Pests in Houses Great and Small

HOUSE OF PESTS

Your house can be a perfect refuge for unwanted guests. This drawing illustrates where pests can take advantage of food sources and habitats within your home.

1 Uncapped chimney Detritus feeders and scavengers p.59; birds p.83

2 Unswept ue Clothes moths and house moths p.22; detritus feeders and scavengers p.59

3 Insect nest Detritus feeders and scavengers p.59; bees and wasps p.69

4 Poorly sealed windows and doors Cluster ies p.65; invertebrate invaders p.68; harlequin ladybirds p.71

5 Open water tank Rodents p.74

6 Damp structural wood Woodborers p.40; damp-loving pests p.51

7 Carpet rolls Clothes moths p.22; carpet beetles p.32; rodents p.74

8 Slipped tile Rodents p.74; birds p.83

9 Imported wood ooring and furniture Powder post beetle p.46

10 Under oorboards Clothes moths and house moths p.22; carpet beetle p.32; detritus feeders and scavengers p.59; mice p.75

11 Damp wood furniture Wood-borers p.40; wood weevils p.57

12 Damp paper and wallpaper Damp-loving pests p.51

13 Damp plaster Fungus beetles and plaster beetles p.56

14 Stored woollens Clothes moths p.22; carpet beetles p.32

15 Wool carpet under furniture Clothes moths p.22; carpet beetles p.32

16 Wool rug Clothes moths p.22; carpet beetles p.32

17 Taxidermy Clothes moths p.22; carpet beetles p.32

18 Damp books Silver sh p.53; booklice p.57

19 Leaking downpipe and blocked gutter Damp-loving pests p.51

20 Vegetation growing against wall Damp-loving pestsp.51; birds p.83

21 Blocked air brick Damp-loving pests p.51

22 Stored food Indian meal moths p.28; detritus feeders and scavengers p.59; ants p.68; rodents p.74

23Bins Flies p.64; rodents p.74

24 Food scraps Rodents p.74; birds p.83

INTRODUCTION

Humans versus pests: an age-old con ict

Humans have been ghting a battle against pests ever since we started to wear clothes, live in dwellings and store food. A pest can be de ned simply as an animal living in the wrong place at the wrong time and many of our most troublesome pest species cause no problems to humans when they are living in their natural outdoor habitats, such as a bird’s nest or a fallen log. Our houses, however, provide a warm, sheltered environment with abundant food and few predators – a far more attractive habitat for many species in which to thrive and multiply than the great outdoors.

The rst historical records of pests infesting homes are from Greek and Roman times. Roman writers, such as Cato the Elder (writing in the second century BC), Pliny and Columella (writing in the rst century AD) recommended many different methods for killing pests. These ranged from religious rituals carried out under a full moon, to the use of y swatters and chemicals, such as burning sulphur, and the application of amurca (the sediment, or lees, that settles from un ltered olive oil). Some of these suggestions were more effective than others: sulphur is toxic to most animals and olive oil lees has an insecticidal effect. Natural insect repellents used in Roman times included rosemary and juniper.

(Above) This second-century mosaic, from the dining room of a Roman villa, depicts the remains of a feast, with a house mouse nibbling a discarded walnut – presumably a common sight

‘To protect clothing from moths: boil amurca down to one-half its volume and rub it over the bottom, the outside, the feet, and the corners of the chest. After it is dry, store the clothing and the moths will not attack it.’

Cato the Elder, de Agri Cultura, c.160 BC.

‘The moth breeds among clothes till that they have bitten it asunder and it is a maniable [ exible] worm, and yet it hides him in the cloth that it can scantly be seen and it breeds gladly in clothes that have been in an evil air, or in a rain or mist, and so laid up without hanging in the sun or other sweet air after.

The herbs that be bitter and well smelling is good to be laid among such clothes as the bay leaves, cypress wood.’

Quotation written in modern English from Laurence Andrew, The Noble Lyfe and Natures of Man, of Bestes, Serpentys, Fowles and Fisshes yt be Moste Knowen, 1521; an English translation of a text from 1491.

(Above) Woodcut showing clothes damaged by moths, in the late-15th-century book from which Laurence Andrew’s text was translated

These Classical texts were preserved in compilations of agricultural lore throughout the early Middle Ages and in medieval times there were many books and manuals offering advice on the best methods for preserving possessions and buildings against attacks by pests. Many advocated physical methods, such as beating carpets to kill clothes moths and carbonising the outside of wooden beams to prevent wood-boring beetles and mould, as well as the application of herbs and other botanicals, such as lavender and tobacco. Although such methods would have had some effect on reducing damage, it was not until an understanding of chemistry was established in the 19th century that really effective insecticide treatments were discovered.

From the 16th century onwards, the mania for collecting specimens of animals, plants and ethnographic objects from faraway places had the most dramatic

Clothes Moths and House Moths

A number of moth species that infest and damage textiles and animal- and plant-based material live in houses in Britain. They are all small and relatively inconspicuous compared with the larger moths we may see attracted to lights in the evening. It is important to be able to identify which species has invaded your home, as they have different habits and food preferences.

Adult moths y into buildings through windows or open doors and birds’ nests are a favourite natural habitat. Dead animals, such as birds and mice, may also provide a source of food and support a moth infestation. The adult moths do not feed and therefore cause no damage; it is the grub-like larvae that feed and damage our clothes and other items. One generation normally takes a year to complete the life cycle, but webbing clothes moths can

(Below) An upholstered chair attacked by webbing clothes moth larvae, leaving a mess of damaged fabric, webbing, frass and cast pupal cases

develop more rapidly if they are warm and undisturbed. The pelleted excreta, or frass, produced by the larvae of moths is frequently mistaken for moth eggs. Frass pellets are hard and opaque, however, whereas moth eggs are very small and translucent, and vulnerable to physical damage. Contrary to popular opinion, clothes moth eggs will hatch within a few days and will not remain dormant in textiles and then hatch many months later.

Textiles soiled with food, sweat or urine are preferentially attacked and a stained area may be far more damaged than an adjacent clean one, because the added nutrients have attracted pests. Pure silk is rarely attacked, but damage to silk clothing is sometimes seen under the arms, round the neck and in the groin. Damage is also more concentrated in dark, undisturbed areas, for example where a wool carpet lies under heavy furniture, in crevices and inaccessible places, behind lapels and in pockets of garments, or where carpets or textiles are rolled or folded. Wool insulation in attics and cavity walls can provide a perfect home. Clean cotton materials are not normally attacked.

(Below) A tiny clothes moth egg hidden in the bres of a woollen garment (Bottom) The life cycle of a moth: it is the larvae of clothes moths and house moths that cause damage, not the adult moths themselves

Key points for carpet beetle prevention:

Regularly check and vacuum-clean wool carpets and rugs particularly areas which are dark and undisturbed, such as under heavy furniture and at the edges of tted carpets.

Regularly check wool clothing in drawers and wardrobes. Look in folded textiles and in pockets and under lapels. Winter woollens are often attacked when put away in drawers in the warm summer months. Once insects have been removed, pest-free items (see below) should be stored in sealed plastic boxes or bags until they are needed. Vacuum-sealed storage bags are particularly useful as they occupy less space and prevent reinfestation.

Check and store felt items carefully. Carpet beetle larvae are particularly fond of wool felt and they will damage box linings and felt in pianos and other musical instruments. They will also sometimes damage book spines when the larvae eat the animal glue.

Store fur and feather items carefully. Like clothes moth larvae, carpet beetle larvae will attack fur and feather items, and old furs, pillows and duvets should be stored in airtight boxes to avoid damage.

Avoid storing spare rolls of carpet. Spare pieces of wool carpet or old rugs kept for years in cellars or attics provide an ideal environment and source of food for carpet beetles. The carpet itself may be extensively damaged and the beetles harboured there may then invade other parts of the house.

 Keep chimney ues clean and clear. As for clothes moths, unswept and unused chimney ues full of material from birds’ nests and perhaps even the carcases of dead birds, can provide an ideal habitat and food source for carpet beetle larvae and lead to an infestation. Chimneys must be regularly cleaned and properly capped to prevent debris from dropping down.

Taxidermy. Specimens may be attacked by carpet beetles. If stored, they should be wrapped in plastic sheeting. Note that some old taxidermy is less vulnerable because of the toxic chemicals used in the preparation of the skins.

Mounted insects. Decorative cases of butter ies and other insects are very vulnerable to attack by larvae of carpet beetles. Well-sealed airtight cases will prevent this.

Items of clothing found to be infested with carpet beetles should be wrapped in plastic and placed in a freezer at -20°C for at least two weeks. This will kill all eggs, larvae, pupae and adults. After treatment, the items can be cleaned carefully and then stored in plastic bags to prevent reinfestation. Rugs, carpets and other textiles can also be treated by deep freezing after being wrapped in plastic. Large carpets or other objects will need to be treated in a commercial freezer.

Books, taxidermy and cases of insect specimens can be treated by freezing (see page 114). Seek advice from a conservator before carrying out any treatment on valuable musical instruments infested with carpet beetle larvae.

infested wood which is moved from damper to drier conditions, but the eggs and young larvae will not survive.

Anobium larvae will attack most wood except sound heartwood, but they prefer starchy hardwood and softwood. Plywood from the rst half of the 20th century is particularly susceptible, because of the added protein from casein and blood albumen, and it can be severely damaged. Woodworm larvae will even develop in books and wood pulp paper when the leaves are compressed, which is why the larvae are sometimes called ‘bookworms’. They will rarely attack clean, dry books, although an attack may spread from infested wooden shelving.

(Top right) Piles of frass from fresh furniture beetle emergence holes

(Above right) Furniture beetle emergence holes in infested sapwood. The adjacent darker-coloured heartwood is not damaged

Korynetes caeruleus

Shiny metallic blue beetles about 5mm long are sometimes found in old houses. These beetles, called Korynetes, and their larvae are active predators of the larvae of furniture beetles and other woodborers. Although these helpful insects are not pests, they indicate the presence of a substantial wood-boring beetle infestation, which should be investigated.

Case study: Furniture beetles at Deal Castle

In the summer of 2013, adult furniture beetles and frass were found by site staff underneath the seat pads of some of the wooden chairs in the Captain’s Flat in Deal Castle, Kent. An investigation revealed old and new beetle emergence holes in the seat pad frames. The room and its contents were checked for other signs of furniture beetle activity and, in addition to the chairs, some of the oorboards, a wooden wardrobe and a large picture frame were found to have signs of emergence. The room and its contents were thoroughly cleaned and the chairs were placed onto a large piece of white sheeting so that staff could monitor for further signs of emerging beetles and frass during the summer months. Staff regularly checked the chairs and the sheeting and a few more dead furniture beetles and frass were found.

As the wooden chairs were not part of Deal Castle’s collection of historic objects, we decided to dispose of the infested seat pads and replace them. All the other wooden items, including the oorboards in the room, were treated with a permethrin micro-emulsion spray (see page 118) in situ as a precaution to prevent further spread of active furniture beetle infestation.

Since then, the objects in the room have been regularly checked and, after two years, no more signs of infestation have been evident. It is now only necessary to carry out good housekeeping measures and regular visual checks during the spring and summer months.

Key lessons:

Identify the source of a furniture beetle infestation and establish which objects are actively infested.

Checking every year for new beetle activity will determine whether an infestation has been successfully eliminated.

(Above right) Fresh furniture beetle emergence holes in the seat frame of one of the chairs

(Right) Infested chairs standing on white sheeting to show up frass from fresh beetle emergence

Prevention and control of damp-loving pests

Silver sh, booklice and other damp-loving insects thrive when there is moisture in their environment. Damp wood, paper and plaster will encourage infestations.

Key points for damp-loving pest prevention:

Eliminate and control damp conditions. Common sources of additional moisture in houses are condensation, poor air circulation and damp penetration through walls and oors. Other causes may be leaking roofs, gutters and downpipes. In most cases, discovery and elimination of the source of moisture leads to a rapid decline in the insect population without the need for any extensive insecticide treatment. Local treatments will relieve immediate symptoms, but are not likely to cure the problem.

Leave air gaps behind books and objects against exterior walls. Air gaps allow the circulation of air and help to prevent dampness and condensation.

Keep air bricks unblocked in older buildings. It is vital to keep air bricks clear to allow free circulation of air.

(Top) Poorly maintained waste pipes and gutters can cause signi cant damp issues leading to infestations by damp-loving pests

(Right) Air bricks should be kept clear to allow air to circulate

Detritus Feeders and Scavengers

There are many species of beetle found in houses that are not serious pests, but which can occasionally cause nuisance or even serious damage if populations are able to build up.

Spider beetles

Spider beetles are so-named because they are super cially spider-like and although they only have six legs, their long antennae can be mistaken for a fourth pair of legs. Spider beetles are common in older houses where they live in birds’ nests and organic debris in attics, chimney ues and cellars. They feed on a wide range of vegetable and animal detritus and will thrive on dried human or pet food. They will also feed on dead insects, and dead cluster ies (see page 65) may provide a good food source if they are not removed regularly.

There are many species, but the adults are usually hairy and generally slow-moving and breed slowly. The Australian spider beetle, Ptinus tectus, is 3–5mm long with a dull brown, hairy body and is common in many cooler countries around the world (pictured top). It is easily distinguished from the golden spider beetle, Niptus hololeucus, (pictured right) which is slightly larger and has a round body covered in shiny golden hairs. This species is becoming more common in historic houses where it often lives in disused chimney ues.

It can be dif cult to proof chimneys and attics to prevent wasps and bees from nesting without compromising ventilation. Blocked ues may also cause damp problems as the air ow is restricted. Removal of old nests is really the only way of avoiding future pest problems.

Mason bees are very different from honey bees as they burrow into soft stone to make an individual nest cell. They normally tunnel in soft limestone and hard sand, but can sometimes be found in large numbers living in the mortar between house bricks. As they are not able to bore into sound mortar, an infestation of mason bees in a chimney is usually a sign that it urgently needs repointing. The bees may be doing you a favour by telling you that your chimney is about to collapse.

Ground beetles

There are many types of ground beetles (called Carabidae) and many are predators forming an important part of the food chain. They range in size from very small beetles less than 3mm long to some of Britain’s biggest beetles over 25mm long. Many are black, but some have an attractive metallic sheen. Although their natural home is outdoors, they are often found coming into houses under doors. It is possible that they do this to shelter from the rain and then cannot nd a way back out. They will do no harm to

the structure or contents of a building, although the larger ones are very active and can cause alarm. They are also often found on sticky pest traps that have been placed near doors and it is possible they are attracted to the other insects caught on the trap.

Harlequin ladybird

Harmonia axyridis

Ladybirds have been using our homes to hibernate during winter months for hundreds of years and are generally welcome as useful predators of green y and other garden pests. In 2003, however, a new species of ladybird was recorded in the UK and has since become a serious nuisance. Originally from the Far East, the harlequin ladybird, Harmonia axyridis, probably spread to Britain on nursery plants from Europe. Once here, it rapidly became established in south-east England and has steadily spread northwards in the last 15 years. It is similar to our native seven-spot ladybird, but is much larger. The common form is red with 19 black spots and cream on the head and thorax, but there is also a black form with 2 or 4 red spots. They will hibernate in houses, sometimes in very large numbers, and being larger than native ladybirds, they

are much more obvious. The adults produce a nasty yellow liquid when disturbed which will stain paint and furnishings. Although they are ef cient predators of garden pests, harlequin ladybirds compete with native species and may even eat them when food is short. For this reason they are regarded as an unwelcome alien species which should be controlled where possible. Removal of the hibernating adults with a brush and vacuum cleaner is the best option.

(Below left) Harlequin ladybirds can gather in large numbers to hibernate inside houses (Below right) Two examples of the black variety of the harlequin ladybird

Birds

Birds are an important part of our environment and many of us enjoy watching them and encouraging them into our gardens. Birds nesting or roosting on, or even in, houses can, however, cause a great nuisance with their noise and droppings, and with insects living in their nests. Even old nests can house insect pests which may then invade other parts of the house. Feeding birds can be well-intentioned, but may also encourage rats and mice, particularly if human food scraps are put out.

A number of bird species have adapted well to living in the urban environment, and can develop very high population levels which have a signi cant effect on the buildings and people living in and around them. Feral pigeons, Columba livia, are the most numerous and troublesome.

Feral pigeon

Columba livia

Feral pigeons can breed throughout the year. Nests are built in or on buildings, under eaves or any other structures that provide support and protection. They are usually found on ledges or in hollows and, in time, and with repeated use, these can become lled with pigeon droppings and debris. Up to four broods may be reared during a year with one or two chicks per brood.

Feral pigeons normally feed in ocks and become highly ef cient at taking food when it is left unattended

for short periods. They rely mainly on spillage around food preparation areas or on food (including bread, cake and seeds) given, spilt or discarded

by people. The size of a feral pigeon population in an area is directly related to the amount of food available.

Feral pigeons can transmit a range of diseases, including ornithosis (a form of psittacosis) and there are proven cases of humans catching the disease from pigeons. Feral pigeons can also carry the food poisoning bacteria Salmonellosis and, although its incidence is low, this public health hazard should not be ignored.

Most damage caused by feral pigeons arises from their infestation of buildings where populations can build up to high levels. Fouling and contamination of structures and statues can occur where the birds nest, rest or roost. This is not only unsightly, but their acidic droppings cause erosion of stonework and mortar. Old droppings can also produce foul smells and may cause allergic reactions in some people. Accumulations of droppings can

Other birds

In addition to pigeons, many different species, including collared doves, rooks and jackdaws, may nest, or attempt to nest, on chimneys. Nest material and birds falling down chimney ues are a frequent source of insect pest problems in houses. Capping of chimneys and

become infested with large numbers of bird mites and insects. The mobility of feral pigeons means that they are able to transmit these infestations from one building to another. Debris and dead birds can also be a food source for ies, moths, beetles, and other insects, as well as blocking ues and rainwater pipes with subsequent extensive damage.

installation of deterrent spikes will usually solve the problem if they are well maintained.

Nesting house sparrows have occasionally caused problems in the past, but the large decline in the sparrow population has now reduced

PEST MANAGEMENT GUIDE

The horrifying discovery that a favourite item of clothing or piece of furniture has been infested and damaged by insects or other pests is often the rst time that people become aware that they have pests in the house. Pest damage does not occur overnight, however, and is usually an indication that pests have been there for a while, making themselves at home, completely unnoticed.

Integrated pest management (IPM) is a process of identifying pests at an early stage and preventing them from living in your house and multiplying. Grabbing a can of insecticide is not usually the right answer: understanding the most appropriate methods for prevention and treatment is the best way of keeping your home and treasured possessions safe from pests.

Successful control of hygiene pests such as cockroaches, bedbugs and eas usually requires speci c techniques and treatment methods carried out by specialist contractors (see page 120).

Recognising the problem

Where do pests live?

Many of our pests are indigenous to the British Isles and can survive outdoors in the winter in sheltered locations. Others, such as webbing clothes moth, will not overwinter outside and need to live in houses all year. In warmer weather, many insects can y around and come into houses through open windows and doors.

Most pests like to live in dark, undisturbed places, particularly where there is organic dirt and debris. This means that attics, cellars, little-used rooms and cupboards are ideal homes for pests to thrive and increase unnoticed.

(Left) A wool rug from Brodsworth Hall, damaged by clothes moths. The damage is concentrated in the lighter area which lay under a piece of heavy furniture. The furniture protected the rug from dirt and fading, but provided a habitat where the larvae could feed undisturbed

living in them and eating large holes. Pieces of wool carpet stored in cupboards or in the attic are also prime sources of food for textile pests. Wool insulation can cause problems as it provides an undisturbed source of food for clothes moths and other pests.

Areas of persistent dampness, such as damp basements or cellars, cupboards against north-facing walls or behind blocked air bricks, or unheated outbuildings, can harbour damp-loving pests such as silver sh, booklice and fungus and plaster beetles. Damp timbers, either in the structure of a building or in furniture and other objects, provide a perfect habitat for furniture beetle, deathwatch beetle and even wood weevils.

Stored food or other organic material can harbour biscuit beetles or Indian meal moths and inadequately stored food and food waste can attract ies, mice, rats or pigeons who may take up residence nearby to take advantage of a readily available source of food.

With the right environmental conditions, pests can exploit any opportunity they nd within your house for an easy meal.

(Below) Wood objects and furniture stored in damp outbuildings can easily become infested by wood-boring insects. Cluttered storage makes cleaning and checking objects impossible

Thatch

Thatched roofs made from reeds or straw can provide a cosy home for many pest species including rodents, birds and insects.

A well-maintained thatched roof will not result in many pest problems, but if it is neglected, animals will take advantage and take up residence.

Mice, rats, squirrels and birds are obvious invaders; less obvious inhabitants will be woodlice, springtails, silver sh, ies, wasps and other insects.

Jackdaws and crows have been known to attack thatch because they are searching for hibernating cluster ies living inside it. Birds will also remove straws for nesting material. Some birds will also use a thatched roof as a handy nest site and squirrels have been known to use them to bury nuts.

Netting is the main way to deter larger pests, such as birds and rodents, from gaining access and causing damage. Rats living in thatch require a source of water to drink and will often take advantage of open water tanks in loft spaces, so make sure that these are always covered.

Keeping a thatched roof in good condition and regularly inspecting it for early signs of pest activity is the best way of preventing pests from becoming established.

(Below left) Neglected thatch can provide a good home for pests

(Below right) Well-maintained thatch with a wire net cover will result in few pest problems

Case study: The battle of the beetles at Brodsworth Hall

Brodsworth Hall in Yorkshire is a special place with an unusual history. The present Hall was built in the 1860s by Charles Sabine Augustus Thelluson and is a magni cent example of what can be bought with a very large mining inheritance. The family’s fortunes dwindled, however, and by the time the Hall came into the guardianship of English Heritage in 1988, it had been badly neglected for over 30 years.

The lack of maintenance had led to decay and destruction of Brodsworth’s stone, timber and building fabric and considerable damage to the house’s unique contents. A ve-year battle against the agents of decay, including rot and insects, then ensued before English Heritage reopened Brodsworth Hall to the public in 1995. Roof timbers damaged by wood-boring beetles were replaced, and room ttings with active furniture beetle infestations were treated with insecticide sprays and fumigated with methyl bromide (an effective treatment, but one that can no longer be used). The moveable house contents were taken off-site for treatment and most of the wool textiles, which were infested with clothes moths and carpet beetles, were treated by freezing. Objects were carefully conserved and returned to the house uninfested.

Continual seepage of water into the house had led to extensive silver sh damage to the wallpaper in some of the ground- oor rooms. Remedial work has stopped the water ingress and the walls are no longer damp, but the damaged wallpaper has been left in situ to show the ravages of neglect.

Ongoing monitoring

The insect monitoring programme started at Brodsworth in 1998 and traps showed that, in spite of all the remedial work, there were still pockets of infestation surviving in the house. Carpet beetle adults and larvae were found in some rooms and large numbers of golden spider beetles were found on traps near replaces. This indicated that there were still quantities of organic debris in the chimney ues. Although the chimneys had been cleaned, they contain inaccessible ledges where bird nests and dead birds can accumulate. The debris is almost impossible to remove now that small boys cannot be sent up chimneys to clean them out. The chimneys have been re-swept many times over subsequent years, and there has been a

gradual decline in the golden spider beetle population as their food source has diminished.

The remedial work to eliminate water ingress resulted in a dramatic decline in silver sh numbers. They are, however, still present in the house in some parts of the ground oor and service wing where there are higher levels of moisture. Stable, low numbers of silver sh can be tolerated, but their numbers are monitored: an increase of these pests would indicate that the environmental conditions in the house had changed and would need to be investigated.

The devastation that can be wrought on wool textiles and taxidermy by clothes moths and carpet beetles has been combatted by a regular and comprehensive regime of excellent housekeeping by the house staff. Regular thorough cleaning of the rooms to remove hair, uff and other organic debris keeps the carpet beetle and case-bearing clothes moth populations to low levels. It is essential to maintain these high standards to prevent the few remaining moths and beetles from increasing in numbers again and causing further damage. There are still pests in Brodsworth Hall, but with good housekeeping they do not pose a great risk to the fragile collections.

Key lessons:

Years of neglect of a historic house can lead to devastating damage to its structure and contents by pests, which can only be remedied by considerable conservation work.

Regular monitoring and checking, coupled with excellent housekeeping regimes, are needed to prevent pests from increasing in numbers and causing further irreparable damage to collections.

(Right, all) These three photographs from Brodsworth Hall show some of the problems caused by neglect of the building. Water seeping into the house caused signi cant damp and the resulting mould and insect infestations damaged the structure of the building, its ttings and contents