UF/IFAS Citrus Magazine - August 2026 by UF/IFAS Statewide Citrus Research and Extension

August 2026 Vol. 2, Issue 1

UF/IFAS

Citrus Magazine From Discovery to the Grove The latest advances in citrus research and management

Welcome

UF/IFAS Citrus Magazine Your Feedback Matters One year ago, in the inaugural issue of UF/IFAS Citrus Magazine, I shared our vision for creating another way to deliver timely, practical citrus research and Extension information directly to Florida citrus growers. Our goal was simple: provide research you can use in a format that is accessible, relevant, and worth your time. As we publish the fourth issue of the magazine, it seems like the right time to ask an important question: How are we doing? Extension has always been built on a two-way exchange. While UF/IFAS faculty work to develop research-based recommendations and educational resources, those efforts are most valuable when they address the real challenges growers face every day. Your feedback helps ensure that our programs remain focused on the issues that matter most in your groves. Over the past year, this magazine has featured contributions from UF/IFAS citrus faculty across Florida, covering seasonal management recommendations, updates on new research, and practical production strategies. We have worked to provide information that you can put to use immediately while also highlighting emerging research that may shape the future of the industry. Whether you receive the magazine in your mailbox or download the digital version, we hope each issue has become a useful resource that you look forward to reading. One comment I have heard repeatedly is that many of you appreciate receiving the magazine as a printed publication. That is valuable feedback, and it tells us that print continues to play an important role alongside our digital Extension resources. But we also want to learn much more. Are we covering the topics that are most important to you? Are there areas of citrus production that deserve greater attention? Is there information you would like to see presented differently? With limited space in each issue, your suggestions help us decide what deserves greater emphasis and where we can improve. I know that Extension programs often ask participants to complete surveys. It can sometimes feel like every meeting ends with another questionnaire. However, this survey serves an important purpose. It will directly influence the future direction of UF/IFAS Citrus Magazine and help us better understand how you prefer to receive citrus Extension information. Photo Credit: Tonya Weeks, UF/IFAS

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If you received this issue by mail, you will find a printed survey enclosed along with a postage-paid return envelope. Simply complete the survey and drop it in the mail. If you are reading the magazine online, or would rather respond electronically, you can scan the QR code or visit the website below to access the online version. You may complete the survey anonymously if you choose. Our goal is to continue making this magazine a trusted source of practical, timely, and science-based information for Florida citrus growers. The only way we can accomplish that is by listening to the people we serve. Thank you for taking a few minutes to share your thoughts. Your feedback will help shape future issues and ensure that UF/IFAS Citrus Magazine continues to provide research, recommendations, and tools that are relevant, useful, and valuable to your operation. As always, thank you for your continued support of UF/IFAS Extension, and I hope you enjoy this issue.

Michael E. Rogers UF/IFAS Statewide Citrus Research and Extension Coordinator

https://go.ufl.edu/magazinefeedback Scan the QR code to provide feedback on the UF/IFAS Citrus Magazine.

Photo Credit: Chris Moran, UF/IFAS

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In Season: What To Do Now! As Florida citrus advances into the fall season, growers should focus on protecting fruit quality, maintaining tree health, and preparing for next year’s crop. Proper horticultural practices are critical for reducing fruit drop and maximizing fruit quality. Pest pressure remains an important concern, as it can affect both fruit quality and tree productivity. For fresh fruit operations, minimizing postharvest decay requires a systems approach that begins in the grove and continues through harvest, packing, degreening, storage, and shipping. Together, careful grove management, timely pest scouting, and strong postharvest handling practices can help preserve yield, improve packout, and maintain marketable fruit quality.

Horticultural Management • Control weeds before harvest • Finish fertilizer applications early • Apply PGRs to reduce fruit drop

Disease Management • Prevent fruit injury during harvest • Keep packinghouses clean and sanitized • Carefully manage degreening conditions • Use fungicides and cold storage strategically

Pest Management Credit: UF/IFAS

• Scout for rust mite damage • Continue ACP management during fall flushes • Protect flushes from leafminer • Monitor mealybug and snail populations

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In this issue.... READ. APPLY. GROW.

Page 26

Page 6

Creating Shade for HLBaffected Florida Citrus

Horticultural Grove Management

Page 9 Fall Fertilization and Fruit Quality

Page 10 Plant Growth Regulators for Fall Application

Page 13 Citrus Insect, Mite, and Snail Management

Page 29 Biological Control Resources for Citrus Pest Management

Page 32 Floods, Pooled Water, and Produce Safety

Page 34

Disease Management

Boosting CUPSchat’s Insights: Adding New Knowledge Improves Fine-Tuning of CUPS Nutrition Management

RESEARCH: WHAT’S NEXT

Page 38

Page 15

Page 18 Solving the ‘LB8-9’ Sugar Belle® Soft Fruit Problem: One Injection at a Time

Page 22 Plant Defense Inducers: A Sustainable Strategy to Reduce Reliance on Conventional Chemicals for Management of Bacterial Diseases of Citrus

Cover Credit: Tonya Weeks, UF/IFAS

An Undercover Assault on Diaprepes Root Weevil

Editorial Committee Ute Albrecht Michelle Danyluk Megan Dewdney Lauren Diepenbrock Mark Ritenour Michael Rogers Muhammad Adnan Shahid Matt Smith Tripti Vashisth Editorial Jamie Burrow Graphic Designer Tonya Weeks

UF/IFAS Citrus Research https://citrusresearch.ifas.ufl.edu

Page 42 Silicon Strategies for Citrus Cold Stress Management

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Horticulture - Read. Apply. Grow.

Horticultural Grove Management Alissa Hevesh and Tripti Vashisth From September through December, citrus trees are primarily focused on fruit growth, maturation, and preparation for the next bloom cycle. During September, most citrus varieties are in Stage II of fruit growth and are moving toward maturation through the fall. This period is especially important because final fruit size, juice quality, peel color development, and overall harvest quality are strongly influenced during this window. Early- and mid-season varieties may also experience significant fruit drop during this period. Therefore, timely irrigation, nutrient management, and applications of plant growth regulators are important for maintaining fruit quality and reducing crop losses. November and December are also important for flower bud induction, which affects upcoming bloom and thus next season’s crop potential. Management decisions made during late fall can therefore influence both the current crop and the following year’s production. This article highlights key horticultural management practices to consider from September through December. For more detailed recommendations, growers should refer to the Florida Citrus Production Guide. Irrigation In most areas of the Florida peninsula, September and October usually receive adequate rainfall. As a result, supplemental irrigation may not be as critical during these months. However, rainfall typically decreases in November and December, resulting in prolonged dry periods. If daily average temperatures remain above 75 °F, trees may still require supplemental irrigation to avoid drought stress. Under these conditions, irrigation every 2–3 days may be needed to keep soil moisture from dropping below approximately 30%. Preventing water stress during this period is important because drought can: •

Reduce photosynthesis

•

Increase pre-harvest fruit drop

•

Promote off-season or prolonged flowering

•

Cause defoliation under severe stress

•

Negatively affects fruit size and quality

Leaf retention is especially important during fruit maturation. Emerging evidence suggests that the number of leaves on a fruiting branch is related to fruit °Brix and size. Therefore, maintaining adequate soil moisture may indirectly support fruit quality by helping

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trees retain leaves, minimize defoliation, and maintain photosynthetic activity. Calendar-based irrigation scheduling can provide a general guide, but it is not always accurate enough to maximize water-use efficiency or prevent nutrient leaching. A more precise approach is to use evapotranspiration-based scheduling. Growers can obtain daily reference evapotranspiration data from the Florida Automated Weather Network (FAWN) and adjust irrigation based on crop water use, soil moisture, and grove conditions.

Weed Management Regular rainfall promotes weed growth, making timely weed management essential because weeds compete with citrus trees for water and nutrients. Unmanaged weeds can also interfere with microjet patterns and with soil-applied pesticides, making harvesting less efficient. When not prevented (through sanitation practices, hand labor, or spot spraying), weeds can be removed via chemicals and mechanical mowing. In late summer and early fall, it is common to apply residual herbicides to maintain a grove with minimal weeds in preparation for and during harvest to maximize efficiency. However, attention should be paid to the herbicide boom shield and off-center nozzle to ensure that low-hanging fruit are not sprayed, as this can lead to fruit drop. When selecting herbicides for weed management, the age of the tree should be taken into consideration, with lower

rates often applied to younger trees. Tree variety should also be considered, as some products are labeled only for some varieties (i.e., oranges but not tangerines).

Fertilization September through December is generally considered a low nutrient demand period for citrus. During this time, the tree is not actively producing major vegetative flushes or setting a new crop. Instead, the main focus is fruit maturation, peel color development, juice quality, and preparation for flower bud induction. Because of this, fertilizer applications late in the fall must be carefully managed.

Citrus

Fruit Variety Display

In general, fertilizer applications should be completed by September or October, depending on variety and crop stage. Fertilization in November and December is not recommended because cooler soil temperatures can reduce nutrient and water uptake, and late nutrient applications may negatively affect fruit quality and tree stress tolerance.

Plant Growth Regulators September through December is an important period for plant growth regulator use in citrus, especially for managing preharvest fruit drop and supporting yield in HLB-affected trees. Preharvest fruit drop is a major concern in Florida citrus. HLB can cause fruit to loosen and drop earlier than normal, and stress events such as hurricanes, drought, flooding, freezing temperatures, and nutrient or water deficits can make fruit drop worse. In some cases, fruit loss may increase several weeks after a stress event, especially following hurricane damage. Fruit drop occurs through abscission, the natural process in which fruit separates from the stem. In HLB-affected trees, this process can begin earlier and progress faster. Hormones play an important role in this process. Ethylene promotes fruit drop, while auxin helps maintain fruit attachment. As fruit matures and senesces, auxin levels decline, making fruit more likely to drop. PGRs, when applied at the right time, can reduce preharvest fruit drop.

December 17, 2026 UF/IFAS Citrus Research and Education Center Lake Alfred, Florida

Summary September through December is a critical management period for Florida citrus. Careful irrigation, fertilization, and PGR timing during this period can improve fruit quality, reduce crop loss, and support both currentseason harvest outcomes and next-season productivity.

UF/IFAS Citrus Research https://citrusresearch.ifas.ufl.edu

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UF/IFAS Statewide Citrus Research and Extension Explore the latest in citrus research from Florida’s leading experts.

https://citrusresearch.ifas.ufl.edu

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Horticulture - Read. Apply. Grow.

Fall Fertilization and Fruit Quality Alissa Hevesh and Tripti Vashisth Fall fertilization, especially with nitrogen, can directly affect fruit quality. Excessive or late nitrogen availability during fruit maturation can delay peel color development, reduce °Brix, and interfere with normal fruit maturation. This is particularly important for fresh fruit, where peel color and internal quality strongly influence marketability and pack-out.

Potassium

When nitrogen levels remain high too late in the season, trees may remain more vegetatively active. This can delay the natural transition from fruit growth to fruit maturation. As a result, fruit may remain greener for longer, color break may be delayed, and juice quality may be less desirable at harvest. Poor peel color and lower °Brix can force growers to delay harvest, which increases the amount of time fruit remains on the tree and may increase the risk of preharvest fruit drop, especially in HLB-affected groves. Late-fall or winter fertilization may also encourage new flush. This can complicate psyllid management and increase the risk of freeze injury if cold weather occurs. For these reasons, avoiding unnecessary fertilizer applications after October is an important strategy for improving fruit quality, reducing risk, and supporting better harvest outcomes.

The timing of a potassium application differs from nitrogen. Citrus trees generally require less potassium in spring during bloom and fruit set, but potassium demand increases during summer and early fall when fruit are growing. Therefore, high-potassium fertilizers are most useful during the warmer months leading into fruit maturation.

Nitrogen Nitrogen management during the fall should focus on maintaining an adequate but not excessive tree nitrogen status. The final split nitrogen application should generally be applied by: •

September for early- and mid-season varieties

•

October for late-season varieties such as ‘Valencia’

During fruit maturation, leaf tissue nitrogen levels of approximately 2.2–2.4% are considered a useful target range. Regular leaf sampling can help guide fertilizer decisions and prevent both deficiency and excessive nitrogen availability. Balanced nitrogen management during this period supports better peel color development, fruit maturation, and harvest quality. In contrast, late or excessive nitrogen can delay color break, reduce °Brix, and increase the risk of delayed harvest and fruit drop.

Potassium is an essential nutrient for fruit development and quality. It is especially important during the later stages of fruit growth because potassium supports cell expansion, fruit enlargement, maturation, and overall fruit quality.

Approximately 60–75% of the annual potassium fertilizer should be applied during late summer and early fall. Late-maturing varieties such as ‘Valencia’ may benefit from potassium applications into October.

Other Nutrients For other essential nutrients, approximately 25% of the annual fertilizer program may be applied during September and October. However, fertilization in November and December should generally be avoided. Late-season nutrient applications may be inefficient because cooler soil temperatures can limit root activity and nutrient uptake. They may also increase the risk of tender flush, freeze injury, delayed peel color development, and poorer fruit quality. The goal during fall should be to maintain tree health without stimulating excessive vegetative growth. A welltimed fertilizer program supports fruit maturation, peel color, increased °Brix, and overall harvest quality.

Summary Proper fall fertilization supports fruit quality, while excessive or late nitrogen can delay peel color, reduce °Brix, and increase fruit drop risk. Nitrogen applications should generally end by September or October, depending on variety, while most of the potassium should be applied during late summer and early fall to support fruit growth and maturation. Avoiding unnecessary fertilizer applications after October helps improve harvest quality and reduce production risks.

Horticulture - Read. Apply. Grow.

Plant Growth Regulators for Fall Application Alissa Hevesh and Tripti Vashisth Gibberellic Acid Gibberellic acid, commonly referred to as GA, can improve tree performance when applied at the proper rate and timing. Field studies in Florida have shown that GA applications can improve yield, reduce fruit drop, and help maintain canopy health in HLB-affected sweet oranges, including ‘Valencia’ and ‘Hamlin’. GA does not directly stop the abscission process. Instead, it helps reduce fruit drop by slowing peel senescence, or aging. By delaying senescence, GA can help retain fruit on the tree for a longer period of time. Repeated GA applications are important. Research shows that GA has a cumulative effect, so multiple applications during the season usually provide greater benefits than a single application. General GA recommendations include: •

Use 20 g active ingredient/acre

•

Apply every 30–45 days starting in July

•

Include a non-ionic surfactant

•

Continue applications through late fall for late-maturing varieties

•

Stop earlier for early- and mid-season varieties to avoid delayed peel color development

For late-maturing varieties such as ‘Valencia’, GA applications may continue through December. For earlyand mid-season varieties, GA should generally not be applied after October because it can delay the peel color break. GA has not been shown to reduce juice °Brix, but it can slow peel aging. Growers should maintain at least a two-month interval between the final GA application and harvest.

2,4-D 2,4-D is a synthetic auxin that can reduce preharvest fruit drop by slowing the abscission process. Unlike GA, which mainly delays senescence, 2,4-D more directly affects fruit attachment by helping maintain the hormonal signal that keeps fruit from separating from the stem. Timing is critical. 2,4-D should be applied before significant fruit drop begins, because it is most effective

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before the abscission process is fully underway. The only 2,4-D product labeled for Florida citrus use is Citrus Fix. General Citrus Fix recommendation: •

Apply Citrus Fix at 3.2 oz/acre

•

Apply during November–December

•

Use for reducing preharvest fruit drop in sweet orange

•

Apply before fruit drop becomes severe

Recent research tested whether multiple low-dose applications of 2,4-D would work better than one labeled-rate application. Results showed that repeated low-dose applications did not reduce fruit drop better than a single labeled-rate application. Therefore, one application of 3.2 oz/acre in November was sufficient for reducing fruit drop in ‘Valencia’.

Combining GA and 2,4-D Recent research indicates that combining GA and 2,4-D can improve fruit drop control because the two products work through different but complementary mechanisms. GA slows senescence, while 2,4-D helps suppress abscission. In a Florida field trial with mature HLB-affected ‘Valencia’ trees, a November application of 3.2 oz/acre Citrus Fix + ProGibb (GA at 10 oz/acre) reduced fruit drop compared with untreated trees. In the first year, the combined treatment reduced fruit drop by approximately 16% compared with the untreated control. In the second year of the study, Hurricane Milton affected the trial site, resulting in higher overall fruit drop across treatments. Even under those conditions, both 2,4-D alone and 2,4-D + GA reduced fruit drop compared with the untreated control. The combined 2,4-D + GA treatment also resulted in higher yield and improved yield efficiency compared with untreated trees. These results suggest that a combined GA + 2,4-D application may be especially useful after stress events such as hurricanes, when fruit drop may increase several weeks after the storm. However, a single combined application should not replace a season-long GA

program. A single GA + 2,4-D spray can help reduce fruit drop, but repeated GA applications are still needed to support canopy health and longer-term tree performance in HLB-affected groves.

Summary Proper use of GA and 2,4-D can help reduce preharvest fruit drop and improve yield in HLB-affected citrus. GA supports fruit retention by slowing peel aging, while 2,4-D helps maintain fruit attachment, and research shows the combination of these products can provide additional benefits. Timing and application strategy are critical to maximizing results and maintaining fruit quality.

Major Categories of Growth-Promoting PGRs PGR Category

Main Purpose

Application Timing

Auxin

Fruit drop

Fall

Cytokinin

Branching, cell division

Spring

Gibberellins

Fruit size, leaf growth, peel integrity

Summer, early fall

These products can be tank mixed. Consider adding to your regular grove management foliar program.

Citrus Phenology

Fruit Set

Flowering Spring vegetative flush

Exponential fruit growth Summer vegetative flush

Save the Date

Fruit maturation Preharvest fruit drop

UF/IFAS Finger Lime Field Day November 4, 2026 UF/IFAS Plant Science Research and Education Unit Citra, Florida

FAWN

Florida Automated Weather Network

Providing weather data for Florida’s agriculture stakeholders https://fawn.ifas.ufl.edu

Entomology - Read. Apply. Grow.

Citrus Insect, Mite, and Snail Management Lauren Diepenbrock The late summer heat often naturally reduces populations of many of our common citrus pest populations; however, under dry and hot conditions certain pests, like citrus rust mite, thrive. If you are a fresh fruit grower, this is a critical time to scout for these populations to reduce visual damage to your fruit. As temperatures cool in September through November, we often see resurgences of several pests.

Asian Citrus Psyllid (ACP) In recent years, we have regulary seen a third flushing period in September, which supports at least one additional generation of ACP. To reduce feeding and reinoculation pressure, continued ACP management through this period is important for tree health.

Citrus Leafminer (CLM) CLM has become a year-round challenge whenever flush are available; therefore, if your groves are flushing, you should consider continued CLM management. Heavy leafminer damage, especially to younger trees, can significantly reduce their photosynthetic capacity. Keeping trees as healthy as possible in the presence of HLB is necessary to protect groves.

Rust Mites (Citrus Rust Mite and Pink Citrus Rust Mite) With a warm, dry fall, rust mite populations flourish and will cause damage to fruit peels. Damage at this time generally appears to be a shiny brown to black coloration, which renders fruit intended for the fresh market unsaleable. For juice fruit, this is less of a concern. Depending on your market goals, be sure to scout and implement a rotational miticide plan to protect your fruit (see the Florida Citrus Production Guide for pesticide recommendations).

Lebbeck Mealybug In the fall, we have a resurgence of lebbeck mealybug, which leads to a higher population going into winter. Because our winter conditions are generally insufficient to knock back this pest, continued management will help reduce the population going into spring and thereby reduce the reproductive population during fruit set in the spring where they do an immense amount of damage.

Bulimulus snails Bulimulus bonariensis, also known as ghost snails, continues to be active until temperatures decrease. At that time, they bury themselves in the soil to persist through the cooler winter periods. While the critical temperatures are yet to be determined, when snail populations “disappear” from groves, they are not gone. They are merely overwintering and will appear again in the spring. Citrus rust mite damage on fruit. Photo Credit: Tonya Weeks, UF/IFAS

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Weeds Highlight : Horseweed (Conyza canadensis) Ramdas Kanissery

Horseweed (Conyza canadensis) is a common broadleaf weed found in Florida citrus tree rows, ditch banks, and along grove edges. This upright annual belongs to the Asteraceae (sunflower) family and thrives under a wide range of soil and environmental conditions. It is established readily in citrus tree rows (Figure 1A). Because a single plant can produce hundreds of thousands of lightweight, wind-dispersed seeds, horseweed can spread quickly through a grove if it is not managed early. Horseweed grows as a single, upright stem covered with short, stiff hairs and can reach 1 to 6 feet tall (Figure 1B). Young plants first emerge as a low-growing rosette before producing a tall flowering stem. The leaves are narrow, arranged alternately along the stem, and give off a carrot-like scent when crushed (Figure 1C). Small flower heads form in clusters near the top of the plant, each with white outer petals (Figure 1D). Horseweed reproduces only by seed, and a single plant can produce approximately 200,000 seeds. Fun Facts Horseweed is also known as marestail, coltstail, and Canada fleabane. The names marestail and coltstail refer to the plant’s tall, narrow flowering stalk, which resembles a horse’s tail or upright broom. Its seeds are built to travel. Much like a dandelion, each seed carries a tiny tuft that catches the wind, and seeds have been found more than a quarter mile from the plant that dropped them. Figure 1. Horseweed growing in a citrus tree row (A), with its stem (B), leaves (C) and flowers (D). Photo Credit: Ramdas Kanissery and Nirmal Timilsina, UF/IFAS

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Horseweed also holds a spot in weed history as the first broadleaf weed found to survive glyphosate, first reported around 2000. Glyphosate resistant horseweed has since spread across much of the country, which is one big reason it can be so hard to control. Management Tips • Control plants while they are small: Young horseweed in the rosette stage is far easier to control than tall, mature plants that have formed a woody stem. Scout tree rows often and treat while plants are small and actively growing. • Mow to keep seed production down: In the row middles, keeping horseweed in check usually comes down to routine mowing as part of your normal vegetation control between the tree rows. Running the mower before flowering keeps a mature horseweed from dropping its heavy load of seed and helps stop seed from building up in the soil and spreading into the tree rows. Just know that mowing can cause horseweed to grow back with several stems, so it pays to stay on top of it and mow while plants are still young and well before they set flowers and seeds. Chemical Control • Include preemergence herbicides: Products containing indaziflam, diuron, flumioxazin, norflurazon, or simazine can help reduce new horseweed emergence. Preemergence herbicides work best on clean soil, so clear existing weeds and debris from the tree row before applying. • Use effective postemergence herbicides: Systemic herbicides such as glyphosate, 2,4-D, and saflufenacil are commonly used to control actively growing horseweed. Because horseweed has developed resistance to glyphosate and some other herbicides in many areas, rotating herbicides with different modes of action is important for keeping control effective. Always read and follow herbicide label directions to achieve good weed control and avoid injury to citrus trees.

Pathology - Read. Apply. Grow.

Disease Management Mark Ritenour and Megan Dewdney Maintaining fresh citrus quality has become increasingly challenging in Florida, especially due to increased tree and fruit stress associated with Huanglongbing (HLB). Even fruit that appear sound at harvest can develop decay during degreening, storage, transportation, or retail distribution if preventive measures are not implemented throughout the handling chain. Successful decay control is rarely achieved through a single treatment. Instead, it depends on a systems approach that begins in the grove and continues through harvest, packing, storage, shipping, and marketing. Every step that reduces pathogen exposure, limits fruit injury, and slows fungal growth contributes to improved packout, longer shelf life, and greater customer satisfaction. Major Decays Affecting Fresh Citrus

Key Practices for Minimizing Fruit Decay

Several pathogens are responsible for most postharvest losses in Florida citrus. During the early season, stemend rots are often the primary concern. Diplodia stem-end rot (Lasiodiplodia theobromae) has become especially problematic in HLB-affected groves because fruit on stressed trees are more susceptible to fungal colonization before harvest. Under suitable environmental conditions, Anthracnose (early season), brown rot (rainy conditions), and green mold (rough handling and/or high spore counts) may also be important. Phomopsis stem-end rot and blue mold can also contribute to losses later in the season, or sour rot, particularly when packingline brushes are not regularly cleaned and sanitized.

Minimize Mechanical Injury

Diplodia stem end rot on fruit. Photo Credit: Tonya Weeks, UF/IFAS

Most postharvest infections begin where the peel has been damaged. Cuts, punctures, abrasions, stem punctures, and impact injuries provide ideal entry sites for decay organisms. Careful harvesting practices, properly maintained equipment, and gentle fruit handling remain among the most effective and economical decaycontrol tools available.

Maintain Excellent Packinghouse Sanitation Sanitation reduces the amount of fungal inoculum present in the packing environment. Fruit, leaves, and debris should be removed routinely from equipment and floors. Decayed fruit should be separated from healthy fruit as early as possible to prevent pathogen spread throughout the packinghouse. Containers, brushes, belts, and fruit-contact surfaces should be cleaned and sanitized on a regular schedule. Good sanitation practices support both decay control and broader food safety objectives. Water sanitation management is equally important. Dump tanks and other water systems should be properly monitored so sanitizer concentrations and pH remain within recommended ranges. Poorly maintained water systems can quickly become sources of crosscontamination.

Manage Degreening Carefully Degreening is often essential for early-season citrus, but it can also increase susceptibility to certain decay organisms. Fruit should be degreened under the recommended temperature, humidity, and airflow conditions. Ethylene exposure duration should be kept to the minimum necessary to achieve acceptable

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area involves chlorine dioxide gas-generating systems. Experimental trials have shown significant reductions in Diplodia stem-end rot following exposure to controlled concentrations of chlorine dioxide gas without causing measurable peel injury under test conditions. Although commercial implementation requires additional refinement, these technologies could eventually provide new opportunities for postharvest disease suppression.

Brown rot on fruit. Photo Credit: Tonya Weeks, UF/IFAS

peel color. Excessive ethylene exposure or extended degreening periods can increase stem-end rot or anthracnose development and reduce fruit shelf life after packing. See https://ask.ifas.ufl.edu/publication/ HS195 for detailed recommendations related to citrus degreening.

Fungicides Remain Important Tools Postharvest fungicides continue to play a critical role in fresh citrus decay management. Materials such as thiabendazole (TBZ) (FRAC 1), imazalil (FRAC 3), and sodium o-phenylphenate (SOPP) have long been used as components of integrated programs. Combinations containing fludioxonil (FRAC 12) and azoxystrobin (FRAC 11) are newer options that can be effective but have not become widely used in Florida because the traditional methods have remained effective. Because decay organisms can develop reduced sensitivity to fungicides, rotating among products with different modes of action remains an important resistance-management strategy. See https://ask.ifas.ufl.edu/publication/CH081 for detailed information on recommended fungicides to control specific types of decays. More recent research in our labs has identified additional promising options for stem-end rot management. Studies conducted over multiple seasons found that propiconazole (FRAC 3) provided strong activity against Diplodia stem-end rot while also offering benefits against sour rot. Natamycin (FRAC 48) demonstrated less activity against Diplodia but may still provide another useful tool as part of an integrated program.

Emerging Technologies Research efforts continue to identify new methods for reducing decay pressure in fresh citrus. One promising

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Preharvest disease management is another method for reducing postharvest decay. Preharvest copper (FRAC M 01) or phosphite (phosphonate) (FRAC P 07) application can be used to help control postharvest brown rot. Further options for brown rot include mandipropamid (FRAC 40) alone or in a mixture with oxathiapiprolin (FRAC 49). While other preharvest fungicides have been extensively studied for control of the other types of decay, the only ones found to have consistent effects on postharvest decay remain unlabeled for citrus.

Temperature and Humidity Management Cooling fruit promptly after packing is among the most effective ways to slow pathogen development. Maintaining the cold chain throughout storage, transportation, and distribution reduces metabolic activity and delays decay progression. However, recommended temperatures vary among citrus types, and excessively low temperatures can result in chilling injury, particularly in grapefruit, lemons, and limes. See https://ask.ifas.ufl.edu/publication/CH081 for detailed information on optimum storage temperatures and https://ask.ifas.ufl.edu/publication/HS191 about chilling injury. Relative humidity also influences fruit quality and decay development. High humidity helps maintain fruit freshness and reduce water loss, while excessively wet conditions can favor pathogen activity. Maintaining appropriate humidity according to packaging type helps balance these considerations and preserve market quality.

Looking Ahead As fresh citrus production continues to adapt to HLB and other challenges, effective decay management will depend on combining multiple complementary practices. Attention to grove health, careful harvesting, sanitation, responsible fungicide use, optimized degreening procedures, and proper temperature management all contribute to success. No single technology will eliminate postharvest decay. However, integrating proven practices with emerging tools offers the greatest opportunity to maintain fruit quality, reduce losses, and deliver consistently highquality citrus to domestic and export markets.

Cover Crop Highlight : Cowpea Sarah Strauss

Vigna unguiculata L. (‘Iron Clay’ cowpea) is a legume cover crop that is well adapted to Florida’s summer growing conditions. As a legume, cowpea forms a symbiotic relationship with nitrogen-fixing bacteria that colonize its roots. Similar to other legume cover crops, such as sunnhemp, the nitrogen fixed by cowpea is returned to the soil when the cover crop is terminated, helping improve soil fertility.

Cowpea growing as part of a crop mixture in citrus row middles. Photo Credit: Sarah Strauss, UF/IFAS

Cowpea grows best when planted at the beginning of Florida’s rainy season, typically in June. Because it has a vining growth habit, planting cowpea in a mixture with a grass species, such as sorghum or millet, can help reduce vine growth into citrus trees while providing additional biomass and ground cover.

Cowpea growing as part of a crop mixture in citrus row middles. Photo Credit: Sarah Strauss, UF/IFAS

Flowering cowpea. Photo Credit: Sarah Strauss, UF/IFAS

What’s happening in research? Solving the ‘LB8-9’ Sugar Belle® Soft Fruit Problem: One Injection at a Time John Chater From a tree health perspective, ‘LB8-9’ Sugar Belle® (SB) is one of the most HLB-tolerant commercial varieties grown in Florida. When it comes to building °Brix, an indirect measure of the sugar content of the juice, few other selections are known to be able to consistently achieve the values seen in a SB mandarin hybrid fruit. This ability to produce fruit with over 15 °Brix is important. Average juice °Brix has been closer to 9 than the 10.5 required for juice to be legally labeled as orange juice in the United States. As a result, processors often import juice from countries such as Mexico and Brazil to blend with Florida juice to meet the legal standard. Recently, research by Dr. Ute Albrecht has shown that oxytetracycline (OTC) trunk injections can improve the °Brix and other fruit quality characteristics in sweet oranges, allowing many growers to meet the minimum juice standard. After discussing SB with a prominent fresh fruit grower, we were encouraged to evaluate OTC injections on this cultivar. That work has produced several interesting findings. Processors also have another option for addressing low °Brix. Federal standards allow up to 10% of orange juice to be blended with another citrus juice, provided the final product meets the legal standard for orange juice. Any blending candidate, however, must have desirable flavor, color, and other quality characteristics. One important consideration is limonin, a naturally occurring bitter compound that can negatively affect juice flavor. Limonin concentrations can also change following pasteurization. Therefore, an effective blending candidate must maintain low limonin levels after pasteurization as well as before. Evaluating this characteristic requires equipment and methods comparable to those used by commercial processors, making collaboration with processors or specialized laboratories essential. In collaboration with one of the major processing companies, we found that SB juice typically maintains low limonin concentrations after pasteurization. SB also has exceptional juice color, producing a deep orange juice compared with the more yellow appearance associated with ‘Hamlin’ and lower quality ‘Valencia’ juice. Combined with its high °Brix, these traits make SB an attractive blending candidate. The citrus breeding team at the UF/IFAS Citrus Research and Education Center (CREC) has also used pasteurized SB juice in informal blind taste panels, where it compared very favorably with commercially available not-from-concentrate (NFC) orange juice.

Like any cultivar, however, SB also has its limitations. One challenge

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Credit: UF/IFAS

Photo Credit: Tonya Weeks, UF/IFAS

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is its relatively high acidity. SB juice often has high titratable acidity (TA), giving it a sweet-tart to tart flavor profile. Fortunately, the high °Brix helps balance this acidity. TA values above 1.2% are generally considered less desirable by Florida growers and processors. However, SB is commonly harvested at about the same time as ‘Hamlin’, which typically has lower acidity. Blending juice from the two cultivars could improve overall juice quality by increasing °Brix while reducing acidity and enhancing color. Even ‘Valenica’ is known to hold higher acid levels with HLB, reaching 1% or greater on average in some historical data. Another limitation is alternate bearing. Some growers have reported yields exceeding 300 boxes per acre in some years, followed by much lighter crops the next season. Alternative bearing is common among mandarin cultivars and is not unique to SB. Because flowering and fruit set can be manipulated in citrus, it may eventually be possible to reduce alternate bearing through management practices such as controlled drought stress or other approaches, although additional research is needed. Perhaps the greatest challenge with SB, however, is soft fruit. Before I joined the CREC, Dr. Fred Gmitter invited me to participate in a discussion with growers about the soft fruit problem and asked me to investigate possible solutions. During those discussions, growers in Central and South Florida consistently reported soft, unmarketable fruit, while growers in North Florida generally did not experience the same problem. Soft fruit has largely been considered an effect of HLB. Although climate change was initially suggested as a possible cause, available weather records did not support that hypothesis. When I started, Dr. Gmitter told me about a man named Mickey Page, a top-notch grower, who was seeing symptomatic fruit in SB. According to Mickey, he was able to reduce symptomatic fruit by hedging during flowering. To see if this worked several years later, Joe Volpe (my graduate student) and I set up an experiment to see if we could reduce symptomatic fruit with hedging at different timepoints. And because hedging at flowering has a thinning effect, we tried an experiment with hand thinning to reduce the incidence of soft and otherwise symptomatic fruit. Neither approach produced the desired results. We also evaluated controlled-release fertilizer, which affected some fruit characteristics but did not adequately address the soft fruit problem. The most encouraging results came from OTC trunk injections. We began injecting SB trees as soon as OTC became commercially available. Although our first year’s applications significantly improved several traits, in-

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cluding °Brix, the injections were made too late in the season for the results to be considered representative. During the following two seasons, trees were injected according to the product label, producing much more meaningful results. One unexpected observation came when the harvest crew inadvertently harvested the second-year research trees at a cooperating commercial grove before data could be collected. Although frustrating from a research standpoint, the fruit successfully made commercial packout, demonstrating that SB fruit can be packable following OTC treatment. After the first full season of properly timed OTC injections, the only significant improvement was an increase in pounds solids per box. No significant differences were observed for °Brix, juice color, or other major fruit quality characteristics. The second consecutive year of injections produced much more encouraging results. Most notably, some fruit remained firm rather than becoming soft. While the response was not observed throughout the entire tree, it represented meaningful progress after four years of research. We harvested fruit that were firm, large, and exceptionally sweet. Even the seeds were well developed and healthy. Although the response was localized, it raises the possibility that injecting both sides of the tree could further improve results. Regardless, these findings demonstrate that SB is capable of producing firm fruit that would likely meet current packinghouse standards. Some growers have told me that SB was always too soft for the fresh market. However, based on what we have observed following OTC injections, this variety can produce fruit that Florida growers can be proud of, and I know for a fact that it produces juice that is exceptional, which is another story for another time.

This season, the CREC citrus breeding team will have fruit and juice displays and juice sensory panels that will include blending agents. We welcome you to come to the UF/IFAS CREC to try some of the blending candidates and fresh market selections for yourself.

UF/IFAS Citrus Research https://citrusresearch.ifas.ufl.edu

Faculty Spotlight: Nabil Killiny

Professor, Plant Pathology UF/IFAS Citrus Research and Education Center Can you briefly describe your current research in simple terms? I am a plant–insect–microbe interaction scientist,

and my research focuses on how plant diseases are transmitted by insect vectors and how this process can be disrupted. I study the molecular and chemical interactions among plants, insect vectors, and pathogens such as Xylella fastidiosa, Spiroplasma citri, Candidatus Liberibacter asiaticus (CLas), and Citrus tristeza virus. My work integrates plant pathology, entomology, chemical ecology, and applied biotechnology to develop sustainable crop protection strategies. My overall goal is to interrupt pathogen transmission by targeting molecular interactions between pathogens and insect vectors rather than relying solely on insecticides.

What question or problem are you most passionate about solving? One of the major areas of my research has been developing improved methods for collecting and characterizing phloem sap, allowing us to better understand the composition of plant vascular fluids. Using these techniques, I have investigated how phloem sap composition influences insect feeding behavior, vector fitness, and pathogen acquisition. These studies also contributed to improved experimental systems for culturing and maintaining CLas under controlled conditions within microbial communities, enabling deeper investigation of its biology, host interactions, and transmission dynamics. These advances provide important platforms for studying one of the most challenging fastidious plant pathogens affecting citrus production worldwide.

What’s a discovery or project you’re especially proud of? I am especially proud of my discoveries identifying key bacterial surface molecules, including adhesins, lipopolysaccharides, and biofilm-associated factors that regulate how Xylella fastidiosa attaches to insect foreguts and is transmitted between plants. I have also identified insect receptor components in Diaphorina citri that are essential for CLas transmission. In addition, I have developed RNA interference (RNAi)-

Photo Credit: Tyler Jones, UF/IFAS

based approaches to silence insect genes involved in physiology and pathogen transmission, providing powerful tools for environmentally friendly pest management.

How has your research evolved over time? Over time, my research has evolved from plant physiological stress responses into an integrated systems approach combining plant biology, insect vector biology, microbial interactions, chemical ecology, and biotechnology. This evolution has enabled a broader tri-trophic perspective on vector-borne plant disease systems.

What’s the most exciting part of your work? One of the most exciting extensions of my work is the development of biotechnological strategies for insect vector management, including attract-and-kill systems and repellency-based approaches that exploit insect behavioral responses to visual and chemical cues. By identifying compounds that regulate attraction and feeding, my research supports sustainable strategies that manipulate vector behavior to reduce pathogen transmission and crop damage.

What’s been the biggest challenge in your research, and how did you overcome it? The greatest challenge has been managing the complexity of interacting plant–insect–microbe systems, addressed through multidisciplinary approaches including molecular biology, microscopy, behavioral assays, and chemical analyses.

What tools or techniques are essential to your work? Essential tools for my research include analytical chemistry, transcriptomics, proteomics, RNAi, qPCR, microscopy, insect transmission assays, phloem sap collection, and chemical ecology approaches. One unexpected finding from my work is that small changes in bacterial surface chemistry or plant phloem composition can dramatically alter insect feeding behavior and pathogen transmission efficiency.

What’s happening in research? Plant Defense Inducers: A Sustainable Strategy to Reduce Reliance on Conventional Chemicals for Management of Bacterial Diseases of Citrus Lauren Fessler Mathews, Ana Redondo, and Ozgur Batuman The Florida citrus industry has battled two major bacterial diseases for decades, citrus canker and Huanglongbing (HLB). Although both diseases were introduced into Florida, they quickly became established and now require ongoing management. For both diseases, one of the primary management strategies is the use of conventional chemical treatments. Citrus canker is typically managed with repeated foliar applications of copper, while HLB has been managed in recent years with annual trunk injections of oxytetracycline (OTC). Both antimicrobial products are widely used in other production systems, where prolonged use has shown that resistant bacterial populations can develop under sufficient selection pressure. Because of this, along with concerns about copper phytotoxicity and environmental contamination associated with both copper and OTC, we explored the use of plant defense inducers (PDIs) as a management tool. Our goal was to determine whether PDIs could help manage these bacterial diseases, reduce reliance on conventional chemicals, and lower the risk of bacterial resistance.

How do PDIs work? Plant defense inducers (PDIs) are compounds that do not kill pathogens directly. Instead, they stimulate the plant’s own immune system, allowing the plant to better resist disease. PDIs activate a range of natural plant defense responses, including the production of antimicrobial compounds, the strengthening of cell walls, the production of pathogen-targeting proteins, and increased antioxidant activity. They can also trigger a whole-plant defensive response known as systemic acquired resistance (SAR), which can reduce the severity of certain infections. PDIs work by activating genes that regulate these defense responses and the signaling pathways involved. Unlike many pesticides, PDIs act on the plant rather than the pathogen, making them broad-spectrum tools that can be effective against a range of pathogens while presenting a low risk of resistance development.

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PDIs for Citrus Canker Management Several commercially available PDIs are already on the market, with additional products currently under development. Previous greenhouse studies have shown that acibenzolar-S-methyl, isonicotinic acid, and other commercial and proprietary PDIs can effectively reduce citrus canker lesion development. To validate these greenhouse results, we conducted field trials in commercial groves in Collier and Charlotte counties to determine whether PDIs, applied alone or in rotation with copper sprays (Kocide® 2000), could reduce copper use while maintaining effective disease control. Treatments were applied to 5- to 8-year-old trees using the program outlined in Table 1. The preliminary results showed that several treatments at both locations reduced the incidence of fruit lesions to levels comparable to those achieved with the standard 21-day copper spray program in mature ‘Hamlin’ trees (Figure 1). These findings suggest that PDIs may provide an effective approach for reducing reliance on copper for citrus canker management and warrant further evaluation.

PDIs for HLB Management Trunk injections of OTC have been one of the most widely adopted HLB management practices in recent years, and for good reasons. Numerous studies have shown that OTC injections improve overall tree health, reduce fruit drop, and increase both yield and fruit quality. However, growing concerns about antibiotic use in agriculture highlight the need for sustainable alternatives that can provide similar benefits. To evaluate this possibility, we tested three plant defense inducers (PDI7, Actigard®, and Regalia®) along with Xytect®, an injectable formulation of imidacloprid that breaks down into a compound very similar to a known PDI. These products were evaluated both as stand-alone treatments and in sequence to determine whether they could improve yield and fruit quality in HLB-affected trees.

Treatment

Application 1st

2nd

3rd

4th

5th

6th

Kocide 21-day

Kocide

Kocide 42-day

Kocide

Actigard

Kocide

Actigard

Kocide

Actigard

Kocide

Actigard

Kocide

Actigard

Kocide

Actigard

Kocide

Actigard

PDI7

Kocide

PDI7

Kocide

PDI7

Kocide

PDI7

Untreated control

Actigard DRENCH Kocide + Actigard DRENCH Actigard SPRAY Kocide + Actigard SPRAY PDI7 SPRAY Kocide + PDI7 SPRAY

Table 1. Treatments applied in the 2025 citrus canker field trial.

Figure 1. Fruit lesion incidence on mature ‘Hamlin’ trees at A) the Collier County commercial plot and B) the Charlotte County commercial plot. Means sharing a common letter are not significantly different, while those with no shared letters differ significantly.

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Figure 2. Graphs depicting fruit quality (pounds solid per box) × yield (boxes per tree) for PDIs used as an alternative to OTC (left) or in sequence with OTC (right) at the commercial ‘Hamlin’ (top), commercial ‘Valencia’ (middle), and experimental ‘Valencia’ (bottom) plots. Means sharing a common letter are not significantly different, while those with no shared letters differ significantly.

The trial was conducted at three locations: an experimental ‘Valencia’ block at the UF/IFAS SWFREC (15-year-old trees), a commercial ‘Hamlin’ block (7-year-old trees), and a commercial ‘Valencia’ block (8-year-old trees). Results from harvest are encouraging. In the commercial ‘Hamlin’ block, Actigard® outperformed the water control. In the commercial ‘Valencia’ block, both PDI7 and Regalia® outperformed the water control and performed similarly to OTC. When applied sequentially with OTC in the ‘Hamlin’ block, all products outperformed the water control, although none provided greater benefits than OTC alone. In the ‘Valencia’ blocks, OTC + Actigard® outperformed the water control at both locations, while OTC + Xytect® also outperformed the water control in the commercial ‘Valencia’ block. Although these results are promising, treatment responses were not consistent across all sites. Additional trials are needed to identify which products consistently provide benefits under commercial conditions. It is also important to note that tree health, or HLB severity, appears to influence activation of SAR. The UF/IFAS SWFREC trees were in severe decline from HLB, received minimal tree care, and did not respond to the SAR inducers evaluated in this study.

Future Directions: Combining OTC trunk injections with PDI sprays In a separate trial, OTC trunk injections were combined with foliar applications of the same proprietary PDI (PDI7). At one location, this combination produced greater harvest performance than OTC alone. Based on

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these results, we plan to further investigate the combined use of OTC trunk injections and PDI foliar sprays as a strategy to manage both HLB and citrus canker. Acknowledgment: We thank our citrus-grower collaborators for allowing us to use their grove sites and for funding from the CRDF (Project nos. 23-014, 24003, and 24-004). We also appreciate the assistance of all Citrus Pathology members who contributed to these studies.

Need a Pesticide License? Looking for CEUs? We can help! https://go.ufl.edu/ceu

Cultivar Highlight : 'C4-10-42' U.S. PPAF John Chater •

Genetic Background: Developed by Dr. Jude Grosser, this selection is a triploid hybrid, meaning it has three sets of chromosomes rather than the typical two, resulting in seedless (technically low-seeded) fruit, similar to seedless watermelon. This hybrid was produced by crossing ‘LB 8-9’ Sugar Belle® with an allotetraploid somatic hybrid of ‘Nova’ mandarin and was obtained via embryo rescue, a common technique in conventional triploid citrus breeding.

•

Fruit Quality and Marketability: This cultivar was selected for its exceptional HLB tolerance and excellent juice quality. Fruit averaged 12.6 °Brix, 1.08% titratable acidity, and a solids-to-acid ratio of 11.8. The average juice color score was 39.1, and the fruit had low limonin content. In a sensory evaluation of 76 accessions, ‘C4-10-42’ was one of only two selections to receive the highest flavor score (38). Pasteurization did not negatively affect flavor.

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Harvest Characteristics: Fruit typically matures from November through December, depending on climate, and can remain on the tree into January.

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Fruit Size: ‘C4-10-42’ produces small, seedless fruit with exceptional flavor and is similar in size to the ‘Tango’ mandarin. It was among the first of approximately 200 accessions to produce fruit in a topwork trial.

Outlook: Yield performance on US-942 rootstock is currently being evaluated at two locations. Long-term compatibility with additional rootstocks is unknown and is under investigation.

•

Performance: On US-942 rootstock, ‘C410-42’ appears to perform well, producing healthy trees in a Polk County grove with high Asian citrus psyllid and Huanglongbing (HLB) pressure despite receiving no oxytetracycline trunk injections. A

(A) ‘C4-10-42’ on US-942 rootstock in Polk County, Florida. The tree is about five years old. Photo Credit: UF/IFAS (B) ‘C4-10-42’ mandarin hybrid is an HLBtolerant cultivar with seedless to low-seeded small fruit that has high external and internal color and an exceptional flavor, suitable for fresh market and juice, although it is not easy to peel. Photo Credit: Tonya Weeks, UF/IFAS (C) ‘C4-10-42’ topworked onto ‘Valencia’ sweet orange on Swingle rootstock in Highlands County, Florida, shown two years after topworking. It has had exceptional health compared to hundreds of other accessions. Photo Credit: UF/IFAS

What’s happening in research? Creating Shade for HLB-affected Florida Citrus Waqar Shafqat, Maryam Khalilzadeh, and Christopher Vincent

Florida citrus growers may be able to improve the performance of Huanglongbing (HLB)affected citrus trees by managing excess sunlight through several techniques. Our research group and collaborators are evaluating several approaches to modifying the canopy environment to improve tree health and productivity under HLB-endemic conditions. Our studies have shown that these approaches can improve tree growth, canopy health, and fruit yield while reducing Asian citrus psyllid populations and HLB disease severity.

Figure 1. (A) Fruit yield (lbs/acre) one year after shade structure installation in five-year-old HLB-affected ‘Hamlin’ orange trees grown under full sun and 30%, 50%, and 70% shade. (B) Fruit yield (lbs/acre) of five-year-old ‘Hamlin’ sweet orange (Citrus sinensis) on Kuharske citrange (C. sinensis × Poncirus trifoliata) rootstock treated with white kaolin particle films, foliar insecticides, or left untreated. Bars represent treatment means, and error bars represent variability around the mean. Different lowercase letters indicate statistically significant differences among treatments.

Among the strategies evaluated, moderate shade (approximately 30%) has provided the best balance between heat stress, protecting trees, and maintaining productivity. Similarly, kaolin particle films have improved tree growth and yield under high HLB pressure. These findings suggest that shading the canopy may be a practical tool for maintaining healthier, more productive citrus trees in HLB-endemic groves. The approaches currently under evaluation include natural shade from other tree species, shade structures, and kaolin particle-film applications. Of these, kaolin particle films are ready for commercial use, while the other approaches remain under evaluation.

How does shade help citrus trees? Shade can benefit HLB-affected citrus trees by reducing heat and water stress during Florida’s hot summer months. Because HLB damages the root system, affected trees have greater difficulty absorbing sufficient water and nutrients. By reducing direct sunlight, shade lowers canopy temperature and slows water loss, allowing trees to maintain healthier canopies and continue grow-

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ing during stressful conditions. Research using shade structures showed that moderate shade improved tree growth and fruit production compared with full-sun conditions. Trees grown under approximately 30% shade produced the highest yields, likely because they received enough protection from excessive heat while still receiving enough light for flowering, fruit development, and photosynthesis (Figure 1A). More shade is not necessarily better. Although increased shade can further reduce heat stress, shade levels above 50% can reduce flowering and fruit production, limiting the benefits of the practice. Kaolin particle films can provide many of the same benefits as shade structures but offer a more flexible approach because they can be applied with conventional spray equipment. By reflecting excess sunlight, kaolin particle films lower leaf temperature, improve water-use efficiency, and reduce heat stress within the canopy. Studies with HLB-infected sweet orange trees found that

Aerial view of newly established shade experiment evaluating pearl, silver, and red shade netting installed before citrus planting (August 2025). Photo Credit: Tyler Jones, UF/IFAS

kaolin particle films improved canopy growth and fruit yield compared with untreated trees (Figure 1B). In addition to improving tree growth and yield, shade may also reduce HLB disease pressure. Studies using shade structures found fewer Asian citrus psyllids on shaded trees. These trees generally produce less intense flushes, making them less attractive to psyllids. Although shade does not prevent HLB infection, the results suggest that shaded trees may experience lower disease pressure while maintaining better growth and productivity under HLB-endemic conditions. Kaolin particle films provide similar benefits. Several research groups have reported that kaolin applications reduce psyllid populations (Figure 2) and delay HLB infection by making leaves less attractive for psyllid landing and feeding. As a result, kaolin particle films provide growers with a practical tool for improving tree performance while also contributing to psyllid management.

Shade Options for Citrus Growers Several approaches can reduce excess sunlight and heat stress in HLB-affected citrus trees. The goal is to protect trees from extreme summer conditions while maintaining enough light for healthy growth and fruit production.

Particle Films The most readily available option for growers is application of particle films. Among the approaches discussed, particle films also have the strongest evidence for delaying HLB infection, reducing psyllid pressure, and improving tree growth and yield. Kaolin particle films are applied with conventional spray equipment and form a reflective coating on leaves and Figure 2. Effect of kaolin particle films on Asian citrus psyllid populations. Plants were observed every two weeks for the first 2.5 years after planting and the total number of psyllids observed on each plant is reported here. White kaolin particle-film treatments reduced psyllid populations compared with untreated trees. The full study was reported in Pierre et al. (2022).

fruit that reduces the intensity of direct sunlight and helps keep the canopy cooler. Because particle films can be applied and adjusted as needed, they may be a practical option for growers looking for a flexible shade-man-

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agement strategy. To learn about how to best apply kaolin particle films, see the particle films page on the UF/IFAS Statewide Citrus Research and Extension website. Our research continues to refine kaolin application programs by evaluating different rates and combinations with other production practices.

Citrus trees protected with individual protective covers (IPCs) and grown near companion tree species. Left: IPC-covered citrus tree located near golden trumpet (Tabebuia spp.). Right: IPC-covered citrus tree positioned near a slash pine (Pinus elliottii). Photo Credit: Waqar Shafqat, UF/IFAS

Shade Structures A second approach under development is the use of shade structures. Shade nets installed over trees reduce incoming sunlight and lower canopy temperatures during the hottest months of the year. Our research has shown that moderate shade reduces heat and water stress while maintaining adequate light for tree growth. Although shade structures require a greater initial investment than particle films, they provide consistent protection throughout the growing season. Current research is evaluating commercial-scale shade netting of different qualities beginning at grove establishment. Preliminary results are expected in 2028. Natural Shade A third option is growing citrus with taller companion tree species that provide natural shade while potentially offering additional ecosystem benefits. Planting citrus beneath taller trees may reduce heat and water stress by moderating the microclimate without excessively reducing available light. Leaf litter and root turnover from companion trees may also improve soil organic matter, water-holding capacity, and nutrient retention. When leguminous tree species are used, they may also contribute nitrogen to the citrus crop. Our research has also found that citrus surrounded by other tree species has very low Asian citrus psyllid pressure. Current studies are evaluating which companion tree species, canopy structures, and spacing arrangements can provide the best combination of shade, citrus

growth, fruit yield, and overall grove productivity. Initial results are expected in 2028.

Looking Ahead Moderate shade offers a promising approach for reducing environmental stress in HLB-affected citrus. By lowering leaf temperature and reducing transpirational demand, shade can improve tree performance under Florida’s high heat and intense sunlight. Shade levels of approximately 30% to 50% appear to provide the best balance between reducing water stress and maintaining sufficient light for growth, whereas excessive shade can reduce photosynthesis and limit tree productivity. Shade should be viewed as a management tool that complements, not replaces, other HLB management practices, including tolerant varieties, sound nutrition programs, frequent irrigation, psyllid management, and trunk injection with oxytetracycline. Future research will evaluate the long-term effects of shade on fruit yield, fruit quality, tree longevity, irrigation requirements, and economic returns under commercial Florida conditions. As HLB continues to challenge citrus production, integrating moderate shade with other site-specific management practices may help growers maintain healthier, more productive trees over the long term.

UF/IFAS Open House

Save the Date 28 | UF/IFAS Citrus Magazine | August 2026 |

November 17, 2026 UF/IFAS Southwest Florida Research and Education Center Immokalee, Florida

What’s happening in research? Biological Control Resources for Citrus Pest Management Jawwad Qureshi Biological control has long played a role in Florida citrus production, but its importance is increasing as growers seek sustainable approaches to managing key pests while preserving beneficial organisms and reducing dependence on insecticides. Advances in mass-rearing technologies, improved understanding of pest-natural enemy impacts and interactions, and growing interest in biological products have expanded opportunities for commercial adoption.

Biological Solutions Gain Importance in the HLB Era Florida’s citrus industry has undergone a dramatic transformation during the past two decades. Since the discovery of Huanglongbing (HLB, citrus greening) in 2005, growers have faced unprecedented production challenges, increased production costs, and declining acreage. Although chemical control remains a cornerstone of pest management, growing economic and environmental pressures have renewed interest in biological control as part of integrated pest management (IPM) programs. Today, biological control in Florida citrus encompasses three primary approaches:

• • •

Conservation of naturally occurring beneficial organisms Augmentation through the release of commercially produced natural enemies Use of commercially available biological products

because successful biological control is reflected by pest populations remaining below economically damaging levels. Our research has demonstrated that biological control can cause substantial mortality of several citrus pests, including ACP, citrus leafminer, aphids, mealybugs, and scale insects. Pests such as Brown Citrus Aphid (BCA) or Florida Red Scale (FRS) are rarely seen in the citrus groves in central and south Florida because aphids and scales are targets of several predators and parasitoids. A recent study did not find FRS in open orchards but did in Citrus Under Protective Screen (CUPS), and a key parasitoid, Aphytis melinus, was observed attacking FRS populations in CUPS. In another recent study, we identified 29 species of phytoseiid mites from traditional open orchards and CUPS and redescribed 7 predatory mites to facilitate the use of appropriate and effective organisms in biological pest control. These and several other studies suggest ongoing impacts of biological control in commercial citrus despite a significant increase in insecticide use after the discovery of HLB against vector ACP. Exclusion experiments conducted in commercial groves from 2020 to 2022 revealed 66-95% mortality of developing ACP immatures that remained exposed to natural enemies. However, this rate of suppression is lower than that observed in the original studies we conducted soon after the discovery of HLB. The increased use of insecticides against the vector psyllid is one factor

The Foundation: Conserving Naturally Occurring Beneficial Arthropods Among the most important natural enemies are lady beetles (Figure 1), lacewings, hoverflies, predatory mites, and spiders. These beneficial organisms attack Asian citrus psyllid (ACP, Diaphorina citri), leafminers, aphids, scales, mealybugs, mites, and other citrus pests. Their contributions often go unnoticed

Figure 1. Common lady beetle predators of multiple pests found in citrus groves.

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contributing to negative impacts on the performance of beneficial organisms. During periods of favorable humidity, fungal outbreaks can also significantly impact psyllid populations. ACP infected with Hirsutella citriformis, Beauveria bassiana, and Cordyceps javanica have been observed in the groves, with H. citriformis being the most common. Although in the last few years we have found a low incidence of H. citriformis. In a study conducted soon after the HLB finding, mummified ACP adult cadavers from H. citriformis infection sometimes accounted for more than 75% of the total number of adults observed during the fall and winter months, but were nearly absent each spring, presumably because relative humidity was suboptimal for the fungus at that time. Temperature, humidity, ultraviolet radiation, and insecticides can significantly influence efficacy, creating challenges for consistent field performance of beneficial organisms under Florida conditions. Another successful example of biological control involves citrus leafminer (Phyllocnistis citrella), a pest that damages young flushes and can exacerbate susceptibility to citrus canker disease. Several native parasitoids and the introduced Ageniaspis citricola have contributed significantly to citrus leafminer suppression. Several predators were also shown to contribute to CLM’s natural mortality. Although leafminer remains present in Florida citrus, outbreaks are generally less severe than they would be without the action of parasitoids and predators. In many cases, naturally occurring predators and parasitoids provide levels of suppression that significantly reduce the need for intervention. Unnecessary insecticide applications during the growing season can negatively affect natural enemy populations, with long-lasting impacts on biological control.

ACP is our primary citrus pest because it serves as a vector for the greening pathogen. During the winter, most citrus trees produce fewer young shoots, limiting ACP reproduction and population growth. The lack of ACP immatures and other pests that feed on young shoots makes citrus groves less attractive to beneficial organisms, which start to colonize groves in the spring. Foliar sprays of broad-spectrum insecticides targeted at overwintering ACP adults significantly reduce their populations and spread during the growing season, when selective insecticides can provide pest suppression and opportunities for functional biological control. Selective pesticide programs, maintenance of refuge habitats for beneficial arthropods, and reduction of unnecessary insecticide applications help preserve populations of beneficial insects and mites already present in citrus groves. Most naturally occurring beneficial organisms are not commercially available and therefore warrant protection to support the development of sustainable IPM programs.

Tamarixia radiata: Florida’s Most Successful Biological Control Agent The greatest biological control success story in modern Florida citrus is the parasitoid wasp Tamarixia radiata. Introduced into Florida to combat ACP, Tamarixia attacks psyllid nymphs by laying eggs on their bodies (Figure 2). Developing wasp larvae consume the psyllid, ultimately killing it. Parasitism rates of 50% have been observed in some locations in Florida and vary based on psyllid populations and insecticide use. Adult Tamarixia also kill psyllids through host feeding, providing additional suppression. Since its release, Tamarixia has established throughout Florida and now occurs naturally across citrus-producing regions. State agencies and research institutions have

Figure 3. Mean mortality (%) of Tamarixia radiata adults after 24 hours of exposure to residues on the field-treated leaves at 1, 3, and 7 days after application (DAA). Means within a DAA capped with the same letter are not significantly different.

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Commercially Available Biological Products

Figure 2. Tamarixia radiata parasitizes an ACP nymph.

mass-produced and released millions of parasitoids, including in urban and residential areas where insecticide applications are limited. However, Tamarixia, like other beneficial organisms, faces a significant limitation due to the use of insecticides in commercial citrus production. Our evaluation of spray residues of insecticides deposited on the leaf surfaces of field-planted citrus showed that the tested chemicals had lethal and sublethal effects on the parasitoid T. radiata. Parasitoid mortality from 1- to 3-day-old residues averaged 90–96% for imidacloprid, 83–94% for fenpropathrin, 38–77% for pyrethrin, 43–44% for Horticultural Mineral Oil (HMO), and 17–33% for spirotetramat (Figure 3). Parasitism by females that survived insecticide exposure was reduced by 71–88% from fenpropathrin, 28–59% from pyrethrin, 31–55% from imidacloprid, 44–4% from spirotetramat, and 39–11% from HMO compared to untreated females. The lethal and sublethal effects of all insecticides on T. radiata were significantly reduced at 7 days after application, suggesting a lower impact on its establishment and performance if releases are made a week after spray application. The value of Tamarixia extends beyond direct pest mortality. Urban citrus trees and ornamental hosts often serve as reservoirs for ACP populations that can reinfest commercial groves. By reducing psyllid numbers in these unmanaged habitats, Tamarixia contributes to area-wide suppression.

The biological products market has expanded rapidly in recent years, reflecting broader trends across agriculture. Commercially available predators, parasitoids, and mycoinsecticides have become valuable components of IPM programs, providing effective, environmentally sustainable alternatives to broad-spectrum insecticides. Predatory arthropods such as ladybeetles Adalia bipunctata, Cryptolaemus montrouzieri, Hippodamia convergens; lacewings Sympherobius barberi, Chrysoperla rufilabris; minute pirate bug Orius insidiosus, and mites such as Amblyseius swirskii and Amblyseius aerialis have been evaluated and found effective in suppressing ACP, aphids, and some pest mites under controlled conditions and warrant field testing. Fungal-based mycoinsecticides, including B. bassiana, C. javanica, and Metarhizium brunneum, are being evaluated for effectiveness against ACP and mealybugs in field conditions and are showing promising results. Biological products can be used as part of IPM programs, whether organic or conventional. Their commercial adoption is driven by several factors, including insecticide resistance, conservation of beneficial arthropods, demand for sustainable production practices, and compatibility with regenerative and environmentally focused management programs.

Implications for the Citrus Industry Biological control is already an important component of Florida citrus pest management, contributing significantly to the suppression of ACP, citrus leafminer, aphids, scales, mealybugs, mites, and other pests. The establishment of T. radiata and other beneficial organisms demonstrates the long-term value of classical biological control programs. Although biological control alone cannot solve crises such as HLB, it offers valuable tools for reducing pest pressure, preserving beneficial organisms, and supporting sustainable production systems. As research continues and commercial products improve, biological control is positioned to become an increasingly significant contributor to the profitability, resilience, and sustainability of Florida citrus production.

Nevertheless, Tamarixia demonstrates that classical biological control can be established permanently, provide long-term pest suppression, and generate economic value.

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Floods, Pooled Water, and Produce Safety Emmy Collins, Billy Mitchell, Taylor O’Bannon, and Michelle Danyluk

How do we define “floods” and “pooled water” in produce safety? In terms of food safety, not all standing water in a field is considered floodwater. After a heavy rain or a problem with an irrigation system, a grower may describe their fields as “flooded.” In the eyes of the Food and Drug Administration (FDA), that water would not be “flood” water but instead “pooled” or “excess” standing water. For the FDA, “flood” water is the water that flows or overflows from open bodies of water outside of the grower’s control. In the Produce Safety Alliance (PSA) Grower Training, “open bodies of water” are called “surface water.” The reason for this difference is that floodwater may contain any number of different unknown hazards, including sewage, chemicals, heavy metals, disease-causing microorganisms, or other contaminants.

Flood events can pose a significant public health risk. Even if a crop is not completely submerged, there is potential for microbial and chemical contamination.

What to do after a flood? The most straightforward flooding scenario for a citrus grower to react to is when floodwaters directly touch the crop. In this case, all food crops the floodwater has touched, either in the field or stored in bulk, are considered adulterated under 02(a) (4) (21 U.S.C. 342(a) (4)) of the Federal Food, Drug, and Cosmetic Act and should not be used for human or animal food. While the official definition of adulterated food by the U.S. Food and Drug Administration (FDA) is more than a page long, in the context of flooding it can be briefly defined as “it bears or contains any poisonous or deleterious substance which may render it injurious to health…” Citrus fruit, regardless of its stage of development, that touches floodwater cannot be harvested for use as human or animal food. Sometimes it is difficult to determine whether the crop was in contact with the floodwater (and has become adulterated). An assessment of the potential effect of the flood on the crop will need to be conducted. If it is determined that the crop did not come in contact with the water or the wet soil, it may be harvested if it is possible to do so without contamination. To quote the FDA guidelines for evaluating the safety of produce from fields that were affected by floods, the likelihood of contamination is low if:

• • • •

Flooding in citrus grove after a hurricane. Photo Credit: C. Oswalt, UF/IFAS

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“The edible portion of the crop has developed after the floodwater receded, or The lowest edible portion of the crop was above the floodwaters level with minimum risk of contamination due to splashing; and The crop can be harvested without cross contamination from nearby environment, including flooded soil and flooded portion of the crop.” If that water touches the harvestable portion of a crop, even if it’s not completely submerged, on the tree, in the field, the packhouse, or somewhere else, there is potential for microbial and chemical contamination

After a flood, best practices include: •

Remove all crops that may have come into contact with flood water

•

Wait 30 to 60 days after the soil has dried before replanting

•

Sample the soil for bacterial pathogens or indicator organisms like generic E. coli if you need to replant earlier

Additional Resources:

Please contact the University of Florida Produce Safety Team with questions and comments: https:// producesafety.ifas.ufl.edu/

•

FDA Guidance for Flood-affected Food Crops for Human Consumption https://www.fda.gov/ regulatory-information/search-fda-guidancedocuments/guidance-industry-evaluatingsafety-flood-affected-food-crops-humanconsumption

•

21 U.S. Code §342 adulterated definition -https://www.law.cornell.edu/uscode/ text/21/342

•

Food Safety for Southern U.S. Food Crop Producers After Flooding -https://www.aces. edu/blog/topics/crop-production/food-safetyfor-southern-u-s-food-crop-producers-afterflooding/

Flooding in citrus grove after a hurricane. Photo Credit: C. Oswalt, UF/IFAS

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Boosting CUPSchat’s Insights: Adding New Knowledge Improves Fine-Tuning of CUPS Nutrition Management Arnold Schumann and Laura Waldo

Introduction to CUPSchat CUPSchat is an artificial intelligence (AI) tool that provides instant, conversational access to information about the Citrus Under Protective Screen (CUPS) production system (Schumann et al., 2026). As of June 2026, it draws on 12 years of CUPS research from more than 100 documents, making it a comprehensive resource for growers and others seeking information on this innovative citrus production system. CUPSchat can be accessed online at https:// citrusdiagnosis.ifas.ufl.edu/CUPSchat/. The purpose of this article is to demonstrate how expanding CUPSchat’s knowledge base can improve its ability to provide user-friendly instructions for analyzing leaf nutrient test results using advanced diagnostic tools such as the Diagnosis and Recommendation Integrated System (DRIS). Because CUPS trees are protected from HLB, they respond efficiently to horticultural inputs, including fertilizer. For example, mature CUPS grapefruit groves can yield up to 800+ boxes/acre/year after the fifth or sixth year, while using only 160 to 180 lbs N/acre. However, the intensive production environment can also lead to transient nutrient imbalances that may limit fruit yield and quality. DRIS provides a rapid method for diagnosing and ranking nutrient imbalances, allowing growers to make targeted fertilizer adjustments.

After updating the knowledge base, we tried conversations with CUPSchat: QUESTION 1: How can DRIS help diagnose CUPS citrus? ANSWER 1: DRIS (Diagnosis and Recommendation Integrated System) is a leaf nutrient analysis tool that can be applied to citrus grown inside CUPS (Citrus Under Protective Screens) to give growers a detailed picture of tree nutrition and to guide fertilization decisions. How it works for CUPS citrus •

Collect leaf samples from trees inside the screened enclosure. Because CUPS trees are protected from the Asian citrus psyllid and HLB, the main nutritional issues are related to growth, fruit quality and the “hidden-hunger” imbalances that often appear in high-yielding, protected systems.

•

Analyze the leaf tissue for the standard set of nutrients (% N, % P, % K, % Mg, % Ca, % S, B, Zn, Mn, Fe, Cu). The results are entered in the DRIS required CSV format (CitrusDRISexample.csv).

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Upload the data to the DRIS web app (https:// citrusdiagnosis.ifas.ufl.edu/DRIS/).

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The program calculates a nutrient index for each element and a “dry-mass” index.

•

Interpret the indices – values that are negative indicate deficiency/low status, values near zero are optimal, and positive values signal excess. The indices are ranked by severity, giving a clear priority list for corrective fertilization. An overall Nutrient Balance Index (NBI) summarizes how balanced the tree’s nutrition is; a lower NBI means a more balanced canopy.

•

Use the information to fine-tune management inside CUPS. Because the screen environment can alter temperature, humidity and transpiration, the DRIS output helps identify “hidden hunger” or specific deficiencies that might not be obvious from visual observation alone, allowing growers to apply the right amount of fertilizer at the right time to maintain high yields and fruit quality.

How did we ‘teach’ CUPSchat to understand DRIS and citrus nutrition? To expand CUPSchat’s capabilities, we added Nutrition of Florida Citrus Trees, Second Edition (SL 253; Obreza and Morgan 2008) to its knowledge base. The second edition is a comprehensive document for citrus nutrition in Florida before HLB disease, which is a good match for healthy trees grown in CUPS. We also added two publications describing DRIS (Schumann, 2020). These additions allow CUPSchat to explain both the theory and practical application of DRIS and to help users interpret results generated by the UF/ IFAS DRIS Calculator, available at https://citrusdiagnosis. ifas.ufl.edu/DRIS/.

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In short, DRIS turns leaf nutrient data from CUPS trees into actionable diagnostic scores, enabling precise datadriven nutrition management that supports the high quality, HLB free production that CUPS aims to provide.

QUESTION 2: Give a brief history and purpose of DRIS, and how CUPS could use it.

with yield potential to generate precise fertilizer recommendations.

How CUPS (Citrus Under Protective Screen) could use DRIS •

Optimizing fertigation – CUPS relies heavily on precise irrigation-fertilizer delivery (precision fertigation) to keep trees healthy under screen houses. DRIS can supply site-specific nutrient balance targets, allowing growers to adjust the fertigation blend in real-time and avoid over-orunder-application.

•

Reducing inputs – One of the documented benefits of CUPS is the lower use of water, pesticides and fertilizers per box of fruit. By identifying exactly which nutrients are limiting or excessive, DRIS helps keep fertilizer rates at the minimum needed for maximum yield, supporting the input-efficiency goal of CUPS.

•

Improving fruit quality and growth rate – Faster tree growth and higher quality fruit are hallmarks of CUPS. Balanced nutrition, as diagnosed by DRIS, contributes to the accelerated growth and better fruit attributes reported for CUPS orchards.

•

Monitoring across seasons – Because DRIS norms are derived from multi-year, multi-location data, they are robust to seasonal variations. CUPS growers can therefore use DRIS to track nutrient status throughout the year, complementing the continuous environmental monitoring (weather, soil moisture) that CUPS already employs.

ANSWER 2: **DRIS – Diagnosis and Recommendation Integrated System** History •

•

DRIS was introduced in the mid-1980s by M. E. Sumner and G. Farina (1986) as a surveybased method for generating nutrient “norms” that describe the optimal concentrations of minerals in high yielding crops (Schumann, 2020). The approach builds on the idea that the uppermost response curve in a yield-vs-nutrient plot represents the true optimum, and it uses data from many locations and seasons rather than single-factor experiments.

Purpose •

It provides a statistical framework for diagnosing which nutrients are limiting, excessive, or imbalanced in a plant population.

•

By dividing a large data set into high-yielding and low-yielding groups, DRIS calculates ratios (e.g., N/P, N/K) that can be compared to the field sample; values that fall in the “shaded” (low yield) zone indicate a problem that needs correction.

•

The system therefore integrates nutrient analysis

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In short, DRIS gives CUPS growers a scientificallybacked, data-driven tool to fine-tune their fertigation programs, reinforcing the system’s goals of higher yields, better fruit quality, and reduced resource use.

Conclusion CUPSchat’s knowledge base was quickly upgraded by uploading documents to include new information about DRIS and citrus nutrition. When asked about using DRIS for CUPS, the answers were informative and relevant for growers wanting to maximize the performance of their CUPS trees by integrating DRIS into their nutrition management. The two slightly different sample questions prompted CUPSchat to provide two answers that were different but covered relevant aspects of DRIS use in CUPS. The examples illustrate the importance of “prompt crafting” to obtain the best results with chatbots. It may be useful to ask follow-up questions in the same conversation to extract more information from CUPSchat.

References cited Obreza, Thomas A., and Kelly T. Morgan. 2008. “Nutrition of Florida Citrus Trees, Second Edition: SL 253 SS478, Rev. 1 2008”. EDIS 2008 (2). Gainesville, FL. https://doi.org/10.32473/edis-ss478-2008. Schumann, A., Waldo, L., & Oswalt, C. (2026). CUPSchat: A Specialized Chatbot for Citrus Under Protective Screen (CUPS) Information. EDIS, (SL538). Retrieved from doi:https://doi.org/10.32473/edis-ss754-2026 https:// ask.ifas.ufl.edu/publication/SS754 Schumann, A. (2020). Computer Tools for Diagnosing Citrus Leaf Symptoms (Part 1): Diagnosis and Recommendation Integrated System (DRIS). EDIS, 2020(4), 1-2. Retrieved from doi:https://doi. org/10.32473/edis-ss683-2020

As with any AI tool, remember, chat models make mistakes. Always verify recommendations before making important management decisions.

CUPS grapefruit grown with fertigation optimized using DRIS. Photo Credit: Arnold Schumann, UF/IFAS

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Rootstock Highlight : US-897 John Chater •

Genetic Background: US-897 is a citrus rootstock developed and released by Dr. Kim Bowman. It is a hybrid of Cleopatra mandarin (Citrus reticulata) and Flying Dragon trifoliate orange (Poncirus trifoliata).

•

Disease and Pest Tolerance: US-897 has been reported to be tolerant to Phytophthora palmivora and the Diaprepes root weevil. This rootstock may be susceptible to citrus blight.

•

Tree Size and Performance: This rootstock has good yield efficiency, which means that it produces a relatively high yield per unit volume of canopy. The fruit quality of US897 has been shown to be higher than that of other rootstocks on late oranges. US-897 is a size-controlling rootstock that reduces the size of the citrus tree compared to a rootstock like sour orange or rough lemon. US-897 has been an exceptional rootstock for CUPS growers with ‘Ray Ruby’ scion, with yields close to 1,000 field boxes per acre at tree maturity. •

Propagation and Availability: This rootstock has been available to growers for many years, and its fruit produces seeds that are mostly true to type, which means this rootstock can be propagated by conventional methods in the greenhouse.

A 3.5-year-old ‘RES 19-56’ U.S. PP36744 early seedless, easy-peel mandarin tree on US-897 rootstock in Polk County, Florida. Photo Credit: UF/IFAS

What’s happening in research? An Undercover Assault on Diaprepes Root Weevil Larry Duncan, Lukasz Stelinski, Lauren Diepenbrock, and Manjul Dutt Diaprepes root weevil (DRW, Diaprepes abbreviatus) has plagued citrus growers in Florida since it was imported from the Caribbean more than 60 years ago. Adults feed on young foliage and lay eggs between older leaves, but the primary damage is caused by larvae feeding below ground. Upon hatching, larvae fall to the soil where they feed and develop on progressively larger tree roots, girdling them and facilitating secondary infections by Phytophthora species. Eventually trees exhibit severe decline or die. The extent of damage is determined by the density of larvae in the soil. DRW is less damaging to trees growing on Florida’s central ridge than in many flatwoods regions because weevil abundance and the incidence of Phytopthora are both significantly lower in the deep, well drained soils Figure 1. Installation of landscape fabric mulch as a soil barrier to citrus root weevils: A) Fabric on the ridge. The reasons applicator to stretch and bury the edges of fabric, B) fabric installed on well-disked soil, C) disked bed after rotovation (right) and rolling (left), D) fabric installed on properly prepared soil, E) experimental plot for the regional difference in with fabric mulch and IPC. Photo Credit: UF/IFAS weevil abundance are poorly understood. Native nematodes the foliage when adulticide toxicity ends. Larvae killed that kill weevil larvae perform better in coarse sandy by an application of entomopathogenic nematodes are ridge soils, but other factors such as differences in soil replaced within a few weeks by neonates falling from drainage and physical/chemical properties are also the canopy to the soil. Prior to the deregistration of likely involved. persistent organochlorine soil pesticides weevils were The detection in 2005 of the devastating citrus greening not a major problem, highlighting the need for longdisease (HLB, Huanglongbing) profoundly shifted the lasting management practices rather than reliance on focus from other soilborne pests and diseases such as available chemical or biological pesticides. An approach DRW, Phytophthora, and nematodes. However, as means that might offer long term, substantial reduction of weevil to improve HLB-affected tree health have developed, larvae in soil is the use of physical barriers that prevent it is apparent that damage to roots by HLB combined most larvae from entering soil or exiting as adults. with that by DRW is unsustainable. The need for better methods of weevil management is urgent, and the key is preventing population buildup in the soil. The difficulty in managing DRW results from the occurrence of different life stages above and belowground and the short residual effects of chemical and biological pesticides. Larvae in soil develop into adults that emerge and re-populate

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Research in Florida, Texas, and California showed that certain landscape fabrics can be used as barriers to prevent the small, newly hatched DRW larvae from entering the soil, and prevent young adult weevils from escaping soil and moving into the tree canopy. A woven weed fabric product (Lumite Inc., Alto, GA), fitted over

soil in pots, prevented soil entry by 99% of neonate weevil larvae. Compared to trees in bare soil, fabricmulched trees in DRW-infested field plots on single row beds near Fort Pierce grew 70% larger after three years. Mulched trees tolerated weevil damage better than trees in bare soil because weevil feeding damage to the roots in each treatment did not differ perhaps because fabric extended only 2.5 feet on either side of the trees. In trials where fabric width was increased to 5 feet on each side of trees, growth of young trees was 31% greater after five years compared to those in bare soil and as few as 1% as many DRW adults were caught in ground traps at the fabric edges as on bare soil. However, the study with wider mulch width did not directly measure the root damage. Fabric mulch beneath lemon trees in California completely suppressed weevil emergence and improved tree health, and research in Florida and Texas confirmed the benefit of fabric mulch for water conservation. Although weevil population control and increased tree growth have been observed in Texas, neither fruit yield, root damage or weevil density have been reported. To date there are no reports of whether fabric mulches in weevil-infested groves affect the fruit yield or the degree to which root damage occurs. With installation cost of landscape fabric exceeding $1000 acre, it is critical to understand if the practice can be profitable, particularly

Figure 2. The height of 5- and 10-month-old trees on Phytophthora resistant or susceptible rootstock, growing on fabric mulch or bare soil and covered or not covered with IPC.

in Florida where profitability has decreased sharply due to HLB. A project was initiated in December 2024 to evaluate the use of landscape fabric mulch for Diaprepes management. The experiment is ongoing in Zolfo Springs and is designed to test the relative value of landscape fabric mulch, individual protective tree covers (IPC) and Phytophthora tolerant rootstocks, in all combinations, in trees exposed to HLB and DRW. The work is funded by Citrus Research and Development Foundation. In addition to the cost of the fabric, installation requires use of an applicator (Figure 1A) to stretch, lay and bury the edges of the fabric. To avoid irrigation runoff, it is critical to use landscape fabric with adequate water filtration (10 gpm/ft2). Bed preparation for the trial was considerably more involved than normal, requiring disking, rotovating and rolling to avoid ruts and an uneven fabric surface (Figure 1B). The planting holes, which were cut with a branding iron, required fabric covers to block weeds, and dams were secured around the tree trunks to prevent dry fertilizer from washing to the fabric edges. Once installed, the fabric plots required vigilance to prevent grass ingrowth from the edges, or weeds from establishing in soil that can accumulate along the irrigation lines or grow from crevasses around the irrigation stakes or tree trunks. The trial is now a grove that can be maintained and

Figure 3. Two weevil species trapped each month in the trial (A) and the total number of weevils trapped on fabric and on bare soil (B).

| UF/IFAS Citrus Magazine | August 2026 | 39

monitored for years to evaluate the effect of fabric soil covers and the other treatments on weevil damage to roots and eventually on fruit production. To date we have seen that all the treatments affected the early growth of the young trees (Figure 2A). Predictably, IPCs boosted the tree size dramatically and fabric mulch added to the early growth. The absence of a significant fabric response a few months later was due to trees reaching the IPC height limitation (Figure 2B). Weevils are monitored with Tedders traps in each plot (64 locations) throughout the trial. To date, the population density of blue green and Diaprepes weevils conform to reports that peaks of weevil abundance occur most often in spring and fall (Figure 3A). It is interesting and perhaps concerning that more weevils have been consistently captured in traps on the fabric than those on bare ground (Figure 3B). Presumably more adults are laying eggs in trees on the fabric which would increase the odds that newly born larvae penetrate the fabric to enter the soil. The preliminary spatial pattern of weevils in the plots also reflects differences in the soil types across the site (Figure 4AB). A majority of weevils have been captured at the grove edges which could result from seasonal migration from outside the grove. But most were recovered from the poorly drained, Ona-Ona soil series, followed by the “somewhat poorly drained” Adamsville fine sand. Few weevils have been captured centrally in the grove on the “moderately well drained” Tavares fine sand. This pattern conforms to anecdotal and published associations between weevil abundance and soil moisture. Future work will characterize the physical and soil food web properties across the site to investigate potential affects of the soil habitat on the

Save the Date Cold Hardy Citrus Field Day

October 8, 2026 UF/IFAS North Florida Research and Education Center Quincy, Florida

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Figure 4. Spatial distribution of citrus weevils (Pachnaeus litus and Diaprepes abbreviates)(A) and soil type (B) in the field trial.

abundance of the pest. It was planned to excavate some of the trees at three years of age to evaluate root damage. However, the trial experienced sub-freezing temperatures as low as 26oF on December 31, January 16 and February 1-3. Microjets were employed during all freeze events except the initial 3 hours on December 31. Damage was immediately apparent and 20% of the one-year-old trees died. They were labeled according to treatment and location, transported to the lab, cleaned and evaluated for root weevil feeding damage (Figure 5 A,B). Tree mortality was correlated (P=0.05) with the cumulative number of weevils recovered in the plots. Fourteen percent of dead trees in plots with fabric ground cover had some evidence of weevil feeding compared to 40% of dead trees in the plots with bare soil. The estimate of damage to roots with visible cortical channeling caused by weevils was 5 times greater (P=0.01) in trees planted in bare soil than trees planted in plots covered by fabric (Figure 5C).

The trial results to date show that fabric mulch can increase the growth rate of young trees and protect their root systems to some degree from feeding by root weevil larvae. As predicted, some weevils manage to enter soil beneath the fabric, but based on the amount of damage to roots, at levels significantly lower than in bare soil. Questions that remain to be addressed in the trial are whether such a reduction in root damage translates into fruit yields high enough to make the use of fabric mulch profitable and whether additional tactics such as IPC and rootstock resistance add value to this approach.

Congratulations

Congratulations to CHRISTOPHER VINCENT on being named a Fulbright U.S. Scholar and for his collaboration on international research in Chile. Figure 5. Weevil damage to roots of mature trees prior to establishing the experiment (A), one-year-old trees that were killed by cold temperature (B), and the difference in weevil damage to roots of one-year-old trees growing on fabric mulch or bare soil in the trial.

| UF/IFAS Citrus Magazine | August 2026 | 41

What’s happening in research? Silicon Strategies for Citrus Cold Stress Management Shahid Iqbal, Davie Kadyampakeni, and Muhammad Adnan Shahid The Florida citrus industry has long been one of the state’s most important agricultural sectors. For decades, citrus production has contributed billions of dollars to Florida’s economy while supporting thousands of jobs in farming, processing, transportation, and marketing. However, the industry has experienced significant challenges over the past two decades, including diseases, hurricanes, climate variability, and declining tree health. Among these challenges, freezing temperatures remain one of the most damaging environmental stresses, particularly for citrus groves located in North Florida.

Silicon helps citrus trees withstand these injuries by stabilizing cell membranes, increasing antioxidant enzyme activity that detoxifies harmful reactive oxygen species (ROS), promoting the accumulation of osmoprotectants such as proline and soluble sugars that protect cells from dehydration, and preserving cellular integrity.

Although growers use several freeze-protection methods, including micro-sprinkler irrigation and protective covers, these practices can be costly, laborintensive, and less effective during prolonged freeze events. As a result, researchers continue to investigate practical and sustainable approaches that can improve the natural cold tolerance of citrus trees.

At the molecular level, silicon acts as a stress-priming agent by activating cold-responsive signaling pathways and defense-related genes. This enables citrus trees to respond more rapidly and effectively when freezing temperatures occur. Together, these protective effects, from cellular membranes to gene regulation, not only reduce freeze injury but also accelerate recovery after freeze events. As unpredictable cold events become more common, silicon is becoming an increasingly valuable component of sustainable, climate-smart citrus production.

How Freezing Damages Citrus Trees

Practical Implications for Citrus Growers

Citrus is a subtropical crop and is naturally sensitive to freezing temperatures. When temperatures fall below critical thresholds, a series of physiological changes occur within plant tissues. First, ice crystals form inside plant tissues, damaging cell membranes. As freezing continues, excessive amounts of reactive oxygen species (ROS) accumulate within plant cells, causing additional damage.

For citrus growers, silicon offers a practical, low-cost,

Freeze damage is commonly observed as leaf curling and wilting, water-soaked tissues, twig dieback, bark splitting, fruit drop, and reduced fruit yield and quality (Figure 1). Severe freeze events may even kill entire trees, requiring costly grove re-establishment.

Why is silicon important, and how does it protect citrus? Silicon is emerging as one of the most promising climateresilient beneficial nutrients for citrus production because it strengthens the tree’s natural defense system against both biotic and abiotic stresses. During freezing events, ice formation within plant tissues causes dehydration, membrane rupture, oxidative stress, and metabolic dysfunction that can result in leaf burn, twig dieback, fruit loss, and even tree death.

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and environmentally friendly tool for improving grove resilience to unexpected freeze events by strengthening the tree’s internal defense system before stress occurs. Applied through soil or foliar applications, silicon improves the tree’s ability to retain water, maintain membrane integrity, and activate antioxidant defenses that reduce freeze-induced injury. Under grove conditions, these benefits translate into less leaf burn, reduced twig dieback, lower fruit drop, and faster canopy recovery following cold events. Silicon also improves overall tree vigor by supporting nutrient balance and photosynthetic efficiency, which helps trees rebuild energy reserves more quickly after a freeze. Importantly, silicon works best as a preventive “priming” tool (Figure 2). Applications made before freezing temperatures occur are much more effective than treatments applied after damage has already occurred. Silicon should therefore be integrated with conventional freeze-protection practices, such as irrigation and wind machines, rather than used as a replacement. For growers facing increasingly unpredictable winter freezes, silicon represents a scientifically supported addition to climate-smart citrus management that can improve both tree survival and long-term productivity (Figures 2 and 3).

How can growers maximize the benefits of silicon applications? Silicon is becoming an important tool for improving plant

growth, increasing tolerance to environmental stress, and supporting overall crop productivity. To maximize its benefits, growers should select products containing monosilicic acid (MSA; H₄SiO₄), the only form of silicon that plants can absorb directly. Because plants continuously absorb monosilicic acid and available silicon declines over time, applications should be made regularly as part of the crop nutrition program rather than as a one-time treatment. Our ongoing research indicates that the greatest benefits are achieved when MSA is applied through both foliar sprays and root applications, allowing plants to absorb silicon through both pathways. When combined foliar and root applications are not practical, growers can still obtain significant benefits by applying 200 ppm MSA as a foliar spray once every month throughout the growing season. For maximum effectiveness, MSA should be applied separately rather than tank-mixed with other fertilizers or nutrients, since tank-mixing may reduce silicon availability and limit its effectiveness.

What other benefits can growers expect from silicon? Although silicon is widely recognized for improving cold tolerance, its benefits extend beyond freeze protection. Our ongoing research has shown that regular applications of monosilicic acid (MSA) can improve several important aspects of citrus production and fruit quality.

Figure 1. Freeze events in North Florida during December 2022 caused massive damage to citrus groves, including fruit drop, reduced quality, and lower yields. Photo Credit: Muhammad Adnan Shahid, UF/IFAS

| UF/IFAS Citrus Magazine | August 2026 | 43

Figure 2. Practical application of silicon on young citrus plants before the freezing events showed great protection against freezing damage. Credit: Photo Muhammad Adnan Shahid, UF/IFAS

Figure 3. Fruit from silicon-treated trees maintained better quality after natural freeze events. Photo Credit: Muhammad Adnan Shahid, UF/IFAS

Trees treated with silicon produced firmer fruit with a longer shelf life, helping maintain fruit quality during storage and marketing. Silicon applications also reduced premature fruit drop, allowing more fruit to remain on the tree until harvest and potentially increasing marketable yield. In addition, we consistently observed lower levels of leafminer damage in silicon-treated trees, suggesting that silicon strengthens the plant’s natural defenses against insect pests.

increasing antioxidant activity, improving osmotic adjustment, stabilizing cell membranes, and maintaining carbohydrate metabolism. However, additional research is needed before full commercial adoption. Future studies will focus on optimizing application rates and delivery methods (soil, foliar, and fertigation), evaluating long-term field performance, and further understanding the molecular and genetic mechanisms responsible for silicon-mediated stress tolerance.

These additional benefits make silicon a valuable component of an overall crop management program by improving fruit quality, tree health, and productivity, as well as increasing tolerance to freezing stress.

Conclusion and Future Research

Additional research will also evaluate responses among different citrus cultivars and rootstocks and examine how silicon can be integrated with other nutrient and stressmanagement strategies. Field studies investigating the role of silicon in improving tolerance to citrus canker and citrus greening are also underway.

Climate change is increasing the frequency of unpredictable weather events, including damaging freezes that threaten Florida citrus production. Developing sustainable strategies that strengthen plant defense systems is becoming increasingly more important.

Overall, silicon is a promising, environmentally friendly, and cost-effective tool for improving citrus resilience. As research continues, it has the potential to become an important component of integrated citrus management by reducing freeze-related losses and supporting the long-term sustainability of Florida’s citrus industry.

Research shows that silicon significantly improves freezing tolerance in citrus by reducing oxidative damage,

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International Citrus & Beverage Conference September 15-18, 2026 Clearwater Beach, FL

Providing Ideas for the Citrus & Beverage Industries Since 1960 The ICBC conference focuses on key issues facing our industry, with talks covering global juice and beverage outlooks to the marketing of new and innovative products. Other talks focus on the impact of new technologies in the processing plants, and interesting new research and consumer insights regarding the beverage category. As always, there are updates on matters that affect the worldwide citrus processing industry. On behalf of UF/IFAS, we hope to see you in September at the conference!

Find out more at https://conference.ifas.ufl.edu/citrus

Scan the following QR code to visit the event website where you will find the latest details about the conference.

Pesticide Information Office https://pested.ifas.ufl.edu/

The UF/IFAS Pesticide Information Office (PIO) provides statewide training for pesticide license certification and recertification for new applicators and experienced professionals every step of the way. Whether you’re applying for your first license, renewing an existing one, or exploring a new license type, you’ll find clear and reliable information. No matter who you are or where you’re starting from, PIO has something for everyone.

Scan the QR code for more information.

Food Safety Event Calendar Fall 2026

Produce Safety Alliance Grower Training A one-day course for produce growers and packers who fall under the FSMA Produce Safety Rule. • September 1st - Marianna https://psa090126.eventbrite.com •

September 23rd - Homestead https://psa092326.eventbrite.com

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September 25th - St. Augustine https://psa092526.eventbrite.com

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October 14th - Jacksonville https://psa101426.eventbrite.com

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December 2nd - Lake Alfred https://psa120226.eventbrite.com

Remote - Produce Safety Alliance Grower Training A three-day, three-hour virtual course for produce growers and packers who fall under the FSMA Produce Safety Rule. • October 6th – 8th https://psa100626.eventbrite.com • November 17th - 19th https://psa111726.eventbrite.com

HACCP for Florida Fresh Fruit & Vegetable Packinghouses A four-day course focused on HACCP principles for fresh fruit and vegetable packinghouses. • August 17th - 20th – Remote https://bit.ly/PackingHouseHACCPAug26

Food Safety Preventive Controls Alliance Training A three-day course which teaches participants how to develop and document a Food Safety Plan for their operation based on the requirements of the FSMA Preventive Controls for Human Foods Rule. • October 20th - 22nd - Lake Alfred https://fspca102026.eventbrite.com Food Safety Traceability Rule Training A two-day hands-on course that provides participants with Food Traceability Rule knowledge and approaches to developing and implementing food traceability best practices. • September 30th - October 1st - Lake Alfred bit.ly/4utryPH

For registration questions, please contact Emmy Collins emilyycollins@uﬂ.edu Sign up for our email listserv: bit.ly/foodsafetylistserv

Upcoming events: producesafety.ifas.ufl.edu

Hurricane Preparedness For Citrus Groves • Rainy season supports citrus growth but brings hurricane threats (June 1 - November 30). • Hurricanes can cause wind damage, flooding, and saltwater intrusion. • Severe damage includes fruit drop, uprooted trees, and suffocated roots. • Quick replanting and water removal within 72 hours are critical. PLANNING AND PREPARATION Timing • Develop hurricane plans ahead of time. • Hurricanes peak in August and September. Plan Goals • Protect people, equipment, and recovery resources. • Maintain adequate insurance coverage. Resources • Local Emergency Management, Sheriff, Chamber of Commerce, and Economic Development offices. PRE-STORM PREPARATION Personnel Assignments • Assign duties for pre-, during, and post-storm. • Set up damage inspection and repair teams. • Maintain contact info for all workers. Safety Training • Train workers on equipment like chainsaws. Liquid Tanks • Keep full to prevent movement and ensure availability. Ditches • Keep clean and drained for post-storm water removal. Cultural Practices • Prune trees regularly to reduce breakage. • Use windbreaks to reduce canker spread and damage. Emergency Equipment • Ensure availability and maintenance of generators, chainsaws, and compressors. • Rent diesel generators (25-60 kW) during hurricane season. Communications Equipment • Ensure radios and cell phones work. • Use hand-held radios with spare batteries for field workers. Hazardous Materials • Secure all hazardous substances. • Shut down gas pumps.

48 | UF/IFAS Citrus Magazine | August 2026 |

Emergency Contacts • List important numbers (utilities, sheriff, medical, etc.). POST-STORM RECOVERY Activity Checklist • Prioritize block-by-block recovery plan. Employee Call-In • Have updated contact list for quick mobilization. Damage Inspection • Use trucks or aerial services (helicopter) for grove survey. Clear Road Access • Remove debris to allow equipment and personnel access. Water Removal • Drain water from root zones within 72 hours. Tree Rehabilitation • Upright toppled trees quickly. • Use pruning saws, loaders, and backhoes. • Paint exposed wood to prevent sunburn. CONCLUSION • Regular pruning is the best pre-storm protection. • Post-storm, quickly: • Clear debris. • Repair irrigation. • Reset and protect trees. • Fertilize and irrigate frequently for recovery.

Adapted from UF/IFAS HS-804 https://go.ufl.edu/hurricaneprep

Damage after Hurricane Milton at UF/IFAS CREC. Photo Credit: Tonya Weeks, UF/IFAS

Publication Highlight

Combining Individual Protective Covers and Homobrassinolide Treatment Prolongs Tree Health and Increases Fruit Yield in Young Tango Mandarin Trees Under Endemic HLB By Saoussen Ben-Abdallah and Fernando Alferez A UF/IFAS study found that combining individual protective covers (IPCs) with homobrassinolide (HBr) sprays improved growth, yield, and health of young ‘Tango’ mandarin trees under HLB pressure. IPCs delayed CLas infection and promoted tree growth, while HBr enhanced canopy development and activated plant defense responses. Trees receiving both treatments showed the best overall performance. Results suggest that combining IPCs and HBr may help young citrus trees stay healthier and more productive in HLB-endemic conditions.

https://doi.org/10.3390/agronomy16141321

Magazine Contributng Authors Fernando Alferez UF/IFAS Southwest Florida REC Ozgur Batuman UF/IFAS Southwest Florida REC Saoussen Ben-Abdallah UF/IFAS Southwest Florida REC John Chater UF/IFAS Citrus REC Emmy Collins UF/IFAS Citrus REC

Larry Duncan UF/IFAS Citrus REC Manjul Dutt UF/IFAS Citrus REC Alissa Hevesh UF/IFAS Extension Highlands County Shahid Iqbal UF/IFAS North Florida REC Davie Kadyampakeni UF/IFAS Citrus REC

Michelle Danyluk UF/IFAS Citrus REC

Ramdas Kanissery UF/IFAS Southwest Florida REC

Megan Dewdney UF/IFAS Citrus REC

Maryam Khalilzadeh UF/IFAS Citrus REC

Lauren Diepenbrock UF/IFAS Citrus REC

Nabil Killiny UF/IFAS Citrus REC

Lauren Fessler Matthews UF/IFAS Southwest Florida REC Billy Mitchell UF/IFAS Gainesville Taylor O’Bannon UF/IFAS Citrus REC Jawwad Qureshi UF/IFAS Southwest Florida REC Ana Redondo UF/IFAS Southwest Florida REC Michael Rogers UF/IFAS Citrus REC Mark Ritenour UF/IFAS Indian River REC

Arnold Schumann UF/IFAS Citrus REC Waqar Shafqat UF/IFAS Citrus REC Muhammad Adnan Shahid UF/IFAS North Florida REC Lukasz Stelinski UF/IFAS Citrus REC Sarah Strauss UF/IFAS Southwest Florida REC Tripti Vashisth UF/IFAS Citrus REC Christopher Vincent UF/IFAS Citrus REC Laura Waldo UF/IFAS Citrus REC

REC: Research and Education Center

| UF/IFAS Citrus Magazine | August 2026 | 49

Florida Citrus Production Guide The latest recommendations from UF/IFAS

New 2026–2027 Florida Citrus Production Guide

Now Available at Your Local UF/IFAS Extension Office or Research Center.

Extension Agents Madelyn Greathouse Sumter, Pasco, and Hernando Counties mgreathouse@ufl.edu Edwin Gutierrez DeSoto, Hardee, and Manatee Counties edwingr@ufl.edu

Alissa Hevesh Highlands County ahevesh@ufl.edu Amir Rezazadeh St. Lucie County amir2558@ufl.edu

Matt Smith Lake and Orange Counties smith197@ufl.edu

Mongi Zekri Charlotte, Collier, Glades, Hendry, and Lee Counties maz@ufl.edu

Danielle Williams Gadsden County dsprague@ufl.edu

Research Faculty Ute Albrecht ualbrecht@ufl.edu

Larry Duncan lwduncan@ufl.edu

Amit Levy amitlevy@ufl.edu

Sarah Strauss strauss@ufl.edu

Fernando Alferez alferez@ufl.edu

Manjul Dutt manjul@ufl.edu

Graciela Lorca glorca@ufl.edu

Barry Tillman btillman@ufl.edu

Yiannis Ampatzidis i.ampatzidis@ufl.edu

Choaa El Mohtar mohtarc@ufl.edu

Xavier Martini xmartini@ufl.edu

Eric Triplett ewt@ufl.edu

Ozgur Batuman obatuman@ufl.edu

Svetlana Folimonova svetlana@ufl.edu

Zhonglin Mou zhlmou@ufl.edu

Nikolaos Tziolas ntziolas@ufl.edu

Bryony Bonning bbonning@ufl.edu

Fred Gmitter fgmitter@ufl.edu

Ahmad Omar omar71@ufl.edu

Tripti Vashisth tvashisth@ufl.edu

Stephanie Brown Claudio Gonzalez stephaniebrown@ufl.edu cfgonzalez@ufl.edu

Nicole Quinn nicole.quinn@ufl.edu

Christopher Vincent civince@ufl.edu

Tom Burks tfburks@ifas.ufl.edu

Jude Grosser jgrosser@ufl.edu

Jawwad Qureshi jawwadq@ufl.edu

Tara Wade tara.wade@ufl.edu

Liliana Cano lmcano@ufl.edu

Zhengfei Guan guanz@ufl.edu

Mark Ritenour ritenour@ufl.edu

Nian Wang nianwang@ufl.edu

José Chaparro jaguey58@ufl.edu

Sandra Guzmán sandra.guzmangut@ufl. edu

Pam Roberts pdr@ufl.edu

Yu Wang yu.wang@ufl.edu

Michael Rogers mrgrs@ufl.edu

Flavia Zambon f.zambon@ufl.edu

John Chater jchater@ufl.edu Michelle Danyluk mddanyluk@ufl.edu Megan Dewdney mmdewdney@ufl.edu Lauren Diepenbrock ldiepenbrock@ufl.edu

Davie Kadyampakeni dkadyampakeni@ufl.edu Ramdas Kanissery rkanissery@ufl.edu Nabil Killiny nabilkilliny@ufl.edu

Arnold Schumann schumaw@ufl.edu Muhammad Adnan Shahid mshahid@ufl.edu

Mark Kistler Lukasz Stelinski mark.kistler@ifas.ufl.edu stelinski@ufl.edu

| UF/IFAS Citrus Magazine | August 2026 | 51

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UF/IFAS

Citrus Magazine August 2026