How to Effectively Manage Codling Moth, WSU Tree Fruit, Washington State University

How to Effectively Manage Codling Moth

Written by: Vince Jones, WSU Decision Aid System. Updated April 13, 2019

Without any intervention, codling moth numbers increase about four-fold from generation to generation. Therefore, targeting the first generation is important to reset the population size to a minimum. Control measures for subsequent generations can be adjusted to the local pest pressure indicated by trap counts.

What’s in the pest control toolbox?

The targets for pest management are the adults, eggs, and neonate larvae which are affected by mating disruption, ovicides, and larvicides, respectively. The combination of these three tools has proven most effective in keeping fruit damage below the economic threshold.

Mating disruption is the first line of defense – it delays and prevents mating and egg laying. Mating disruption dispensers need to be in place by roughly 100 DD or bloom, before the first adults emerge at 175 DD; these typically last all season long. Mating disruption is particularly effective as the temperatures increase and will dramatically improve the activity of pesticides applied during the season.

Ovicides are the second line of defense. Eggs can be prevented from hatching with topical or residual pesticides. Oil is a preferred option; it suffocates the eggs that have been laid. Its residue is short – only about 1 day, however, because it kills eggs that have already been laid, it has an effective residue of 150 DD (the length of the egg stage). This is extremely important because it makes oil applications very effective in the early spring compared to the codling moth granulosis virus (discussed below). Oil also tends have a relatively minor effect on natural enemies so it is compatible with Trichogramma parasitoids that have been shown to help suppress codling moth populations by attacking the egg stage.

The third line of defense is larvicides, such as conventional larvicides or codling moth granulosis virus. Both target the newly hatched codling moth larvae which almost immediately bore into the fruit. Therefore, precise application timing is important, because once larvae enter the fruit, they are protected from pesticides. Granulosis virus has a relatively short residual activity (5-7 days), so it is best used in the second generation. Conventional insecticides tend to be active from 12-17 days, so residual activity period is not so sensitive as with the granulosis virus.

What’s the best insecticide application timing?

In conventionally treated orchards, the delayed first cover strategy is the best management strategy. This program uses an oil applied at 375 DD to prevent any eggs that have already been laid by that time from hatching. This means that, after this oil application, no newly laid eggs will hatch for another 150 DD (duration of the egg stage). This allows the first larvicide cover spray to be delayed by 150 DD until 525 DD. At that point, the larvicide with its longer residue is active during the majority of the egg hatch period. A second larvicide cover spray is timed depending on the pesticide’s residual activity period. For conventional programs, it is typically about 14 days (see table). So, overall, only the oil spray and two additional sprays would normally be needed to control the first codling moth generation. Sampling at the end of the generation gives a good indication of the efficacy of the program and the need to treat later generations. In many situations, if you are using mating disruption, and the population was under control the previous year, you may not need the second cover spray unless migration from untreated areas occurs.

Organic programs should always use mating disruption, without it, codling moth control is extraordinarily difficult. Compared to the conventional application timings, organic timings are slightly different in that the residue of granulosis virus is fairly short (5-7 days) and during the first generation it is rare that the residue gives as good a control as oil alone. The application of oil at 375 DD, should be followed by 2-3 more applications of oil at 150 DD intervals during the first generation. As with the conventional program, sampling at the end of the generation gives a good indication of the efficacy of the program and the need to treat later generations.

Whether the second and third codling moth generations require additional insecticide applications depends on the pest pressure. It is not always necessary to treat every generation to prevent damage. Remember, mating disruption is still active and keeps reducing the number of eggs laid, which in turn reduces the need for supplemental sprays. Careful monitoring of adult flight with pheromone traps, larval sampling at the end of each generation, and knowledge about potential infestation sources (such as bins or nearby untreated areas), are essential in determining when treatments are really needed. And even if traps show an unexpected increase in numbers in the next generation, a well-timed intervention will knock down the population again.

If sprays are required in organic orchards in the second generation, a oil only treatment program (as used in the first generation) is not recommended because excessive oil applications can reduce tree vigor. In this case, the residue of virus during the summer gives good control of codling moth larvae when used with a delayed first cover program.

The time of year also plays a role in pest pressure. After August 20th, all newly-hatched larvae are destined for diapause because of changes in day length. While those larvae still pose a risk for damage and may need supplemental pesticide application, they will not complete development this year into adults that could lay more eggs. Instead, they will enter the pool of diapausing codling moth that will emerge next spring.

See also:  Greenhouses, Plant Biology

As a general goal, the number of larvae reaching the overwintering stage should be kept as low as possible. The occurrence of a full fourth generation of codling moth, as occurred in 2015, adds more diapausing larvae to the overwintering population unless orchards are protected. Low overwintering numbers, however, lay a good foundation for soft and low-input programs in the following year. Always expect higher codling moth pressure the year following the occurrence of three or more generations of codling moth adults.

Management strategies and timing for codling moth control. Mating disruption should always be used.

Management Strategy Sprays per
CM Generation
Spray Timing
Conventional Delayed First Cover 3 1 st spray: oil just before egg hatch (375 DD)*

2 nd spray: larvicide at 525 DD (“delayed”)

3 rd spray: larvicide 14 days after 2 nd spray

Organic oil

Only in first generation

3 1 st spray: oil just before egg hatch (375 DD)**

2 nd spray: oil at 525 DD

3 rd spray: oil at 675 DD

Organic Delayed First Cover, virus

(only if needed based on scouting and only in second or later generations)

4 1 st spray: oil just before egg hatch (1375 DD)***

2 nd spray: virus at 1525 DD (“delayed”)

3 rd spray: virus 7 days after 2 nd spray

4 th spray: virus 7 days after 3 rd spray

*For second generation treatments based on need: add 1000 DD to timings above for each generation treated after the first generation.

**Do not use an oil only program in generations after the first

***For third generation treatments: add 1000 DD to timings above; do not use this program in the first generation.

Additional Resources

For specific timings view the Decision Aide System

For a listing of codling moth materials see the WSU Crop Protection Guide


Department of Entomology, Washington State University
Tree Fruit Research & Extension Center


Moth infestations can be a persistent problem if left untreated. The best way to protect your valuables from moth damage is to put in preventative measures and monitor signs of an infestation to counter an infestation early.

A variety of moth species and their larvae feed on textiles such as wool, hair, fur, feathers and debris. Some moths feed on stored food.

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Agent of Deterioration: Pests

by Tom Strang and Rika Kigawa

Table of Contents

List of Pests

Pest Organisms

Pests Footnote 1 ; are living organisms that are able to disfigure, damage, and destroy material culture (Figure 1).

Figure 1. Dermestid beetle larvae have eaten the decoration on this Naskapi hide mitten because the pigment binder has greatly increased the nutritional value for the larvae.

As human habitation and agricultural activities have increased, many pests have adapted to and found niches in our buildings and our undertakings. These pests have moved around the world and proliferated through trade and travel.

Microorganisms, insects, and rodents represent the majority of pests affecting cultural heritage. These three subtypes are significant risks in the north-temperate Canadian environment. Other pests, such as roosting birds, molluscs (marine borers), bats, other invasive mammals, lizards, etc., may be significant despoilers in specific locations, but are not as predominant worldwide inside collection spaces.

There are 830,075 described species of insects, 100,800 species of fungi, and 4,496 species of mammals (Lecointre and Le Guyader 2006 ). While pests are but a fraction of these species, a complete list of pests would be too large for the scope of this document. «Pest» will therefore be defined in general terms by the given subtype accompanied by some common examples; however, the control strategies will not be oversimplified.

Non-pest organisms

In nature, there are dependencies and competition among organisms. For example, «beneficial» organisms (spiders, centipedes, and parasitic wasps) prey on pests. On close observation, these non-pest organisms will be seen in collections. As with pests, their presence may also be objectionable, causing modest soiling, and indicating that a collection enclosure is not sealed properly.

Non-pest, «non-beneficial» organisms can also be found in collections (e.g. sowbugs, millipedes). They sometimes indicate a pest problem because of their association with certain environmental conditions or their association with the presence of building perforations. Their presence may be objectionable for the reasons stated above. As well, their bodies may provide food for some pest species. Therefore, controlling these organisms is usually undertaken, preferably by keeping them out.

Pest Subtypes

Pests can be subdivided by biological classification or by the materials they attack. Correctly identifying pests is the first important step in learning the inherent biological limitations of each organism infecting a collection. These limitations are then exploited in order to control them. Be aware that within the pest subtypes, the materials that are attacked will vary. As well, the species within subtypes may have specialized abilities that enable them to exploit or to withstand control measures.


Fungi (moulds) and bacteria are numerous and ubiquitous. Mould spores and bacterial spores can be airborne or carried along with other particulates. Bacteria are commonly brought into a collection area by contaminated floodwater or can form in standing water in buildings. Fungal hyphae are the destructive phase of mould. The actions of the hyphae stain and digest objects (Figure 2).

Figure 2. Mould colonies on the back of a framed print. Their distribution shows the effect of a microclimate created by the varying distance the backing board hung away from a damp wall. Where the gap was wider (top of picture), ventilation could occur by convection; this prevented moisture from building up to levels that allow mould growth. Where the gap was narrow (bottom of picture), the convection of ventilation was restrained; this allowed enough moisture to support mould growth to diffuse to the backing board.

Microorganisms digest, stain, weaken, convey moisture (e.g. «dry rot» fungi), and attract insect pests by modifying and augmenting the nutritive value of an object. Aside from the pathogenic effects of infection, bacteria and fungi pose a health risk to humans simply through high concentrations or chronic exposures that lead to allergic and severe respiratory conditions. Using effective personal protective equipment is strongly advised when working with microorganism contamination (Strang and Dawson 1991 a; consult Guild and MacDonald 2004 for current recommendations on working with mouldy collections).


Insects and other arthropods are the most numerous animal pests. Because of their specialization, small size, mobility, sensory capability, and fecundity, insect pests are a persistent threat to the collections they favour (Figure 3).

Figure 3. Anobid beetle larvae have chewed most of the wood away from this table’s leaf support. Very little activity is seen, however, on the exposed varnished surfaces.

Insects can have very specialized food requirements; therefore, the hazard they pose should be thought of in terms of material type, not object type. Insects are normally present in the natural environment and find their way into collections. Or, they enter collections from infested objects that are sent on loan or are newly acquired, much as insect pests are carried around the world through trade and travel.

Insect life cycles vary. The two common patterns are:

  • egg → larval stages → pupae → adult
  • egg → nymph stages → adult

Larvae and nymph stages are marked by more or less constant eating and growth. This encourages multiple moults as the insect outgrows its hard integument (outer shell). Adult forms may not eat (e.g. clothes moths), may eat different foods than they do in their larval stage (e.g. dermestids), or be as voracious as larvae are on the object (e.g. Stegobium) Footnote 2 . Pupation may occur away from the food substrate, which decreases the chance the pupa will be preyed upon. Adults may also seek alternative sites to meet mates (e.g. dermestid adults meet on flowers where they also eat the pollen). Insects often rely on pheromone cues to find mates (e.g. clothes moths and wood-boring beetles). Some insects disperse quickly throughout collections, while others tend to stay in one place and reinfest the same materials over subsequent generations. However, the potential to spread is always present.

Insects, and less commonly other arthropods, in their need for food and shelter cause damage ranging from incidental soiling to complete digestion of organic materials. Some insects will also bore into soft plastic foams and materials composed of minerals to lay their eggs or to pupate. Some insects transmit human diseases. The presence of food pathogens, insect body parts, and faecal matter in collections can induce allergic reactions in humans. Therefore, precautions similar to those for handling mouldy material should be used when working around insect-contaminated objects.


Rodents are the most dominant mammalian pest in agriculture and commerce. They are usually present in urban or rural localities. (Alberta is the major exception: its long-running, province-wide rat extermination program has been very successful.) Rats and mice easily climb, burrow, swim, and gnaw. They are also very fecund. Because they are often associated with human food and garbage, they are frequently found in collection buildings. They usually establish home ranges within a 20- to 60-metre radius, but may range even farther.

Mice usually establish territories within a 20-metre radius, or even smaller areas inside a building, but can range farther abroad, even up to a couple of kilometres. They breed quickly and, thus, will spread out looking for more resources (food, water, and nesting material). They may find these resources easily available in collection rooms. Rats also live in colonies. They live in established burrows outside buildings or in nests inside a building. Because all rodent pest activity is strongly associated with food availability, control activities are often aimed at making these resources unavailable.

Rodents gnaw all the time on non-food items to deliberately wear and sharpen their constantly growing teeth. They cache food for future use; urinate to form trail marks and deposit faeces as they explore; leave grease marks along trails; disrupt material by gathering nest materials; and create shelters in protected locations (Figure 4).

Figure 4. Rats have left distinctive grease marks on the walls where they constantly rub as they move around their range. Photo: Department of Integrated Pest Management, University of Aarhus.

Dead rodents, sloughed hair, and faecal matter attract and support keratin- and protein-eating insects, which then can spread into collections. A number of human diseases are transmitted from rodent waste; therefore, using respiratory protection and barrier-protective clothing is advised when cleaning any rodent-infested material.

Birds and bats

Several species of birds roost or build nests on buildings. Their nests and faeces soil and deface the supporting structure. This detritus supports populations of keratin- and protein-eating insects. Their nests also harbour parasites. Exposure to avian source dusts (created from faeces, feathers, and nesting materials) may enhance the development of bacterial and viral zoonoses (e.g. chlamydiosis in pigeons and poultry) as well as cause chronic allergic responses. These reasons, along with disturbing patrons by defecating in public spaces, are incentives for suppressing birds (most often pigeon flocks). Accumulations of bird guano (e.g. in attic roosts) can pose microbial human health hazards if this dust is inhaled (e.g. histoplasmosis, cryptococcosis); therefore, full respiratory protection, barrier-protective clothing, and post-exit sanitary practices are advised if entering these spaces or removing such wastes (Strang 1991 b). Several prevention methods can be used to reduce bird roosting in vulnerable locations (Figure 5).

Figure 5. Anti-bird roosting spikes on this heritage building protect patrons and the structure from soiling.

Sensitivities of Collections to Pest Attack

What pests want

The object stands in for what the pest would normally search for (food, water, or nesting materials) in its natural environment.

Surface effects from infestations range from cobwebs and dried faecal excretions, to urine stains and agglomerations such as bird nests, and mud wasp and paper wasp nests. These surface effects can permanently mar an object’s vulnerable finishes or accelerate a microbial attack on an object.

Grazing and gnawing activities are accelerated by surface deposits and salts that attract a pest, or by the pest’s need to chew. Pests chew and digest these materials, not the objects per se. Their attraction to particular objects may be further increased by the object’s design if it facilitates access (e.g. the rough surface of an exposed end grain that allows the wood borer to lay its eggs) and shelter, or by residues on the surface. Whatever the reason, it is the pest’s native ability to recognize and utilize the material that stimulates and sustains pest damage.

In describing the risks, listing some representative object classes will indicate the vulnerability of materials and the possible extent of pest risk. (Consult Materials, objects, and common damaging insect pests, which uses familiar curatorial categories of materials.)

Sensitivities to moulds

All organic and inorganic surfaces can be colonized by moulds under the right conditions of high humidity and dispersion of nutrients. Damp cellulosics (paper) and proteinaceous (parchment) materials are the most affected because they are entirely digestible, relatively soft, and can be hard to clean at the porous cellular level where microorganisms contaminate an object (e.g. invasive fungal hyphae, tiny spores with strong pigmentation). Paper and parchment objects often have high information content (text, illustrations, etc.), so the obscuring effects of microorganisms are often gravely disfiguring. Moulds will also grow on inorganic surfaces in the presence of nutrients and moisture. The ability to identify microorganisms and their degree of risk to people and materials requires special equipment and training. Being able to distinguish surface mould from dust and other soiling matter is a useful skill that will help guide preventive conservation decisions.

Sensitivities to insects

Due to insects’ specialization in feeding, burrowing, and breeding activities, there is a wide diversity in a collection’s vulnerability to specific insects. However, some insect pests are generalists, and will affect related groups of materials.

Insects are specialized in their feeding habits due to differently adapted mouthparts, digestive systems, and symbionts (e.g. gut-dwelling microorganisms that convert cellulose to usable sugars). For example, different insects are attracted to dry seeds and to starch-adhesive pasted paper. Although both objects are largely starch-based, weevils are more likely to attack dry seeds and silverfish are more likely to attack starch-adhesive pasted paper because of their different mouthpart structures.

Soiling of objects increases their susceptibility to pest attack, in particular silk and cotton fabrics. These fabrics are not usually eaten as food by insects without the presence of added nutritional materials.

Consult Materials, objects, and common damaging insect pests for a material’s vulnerabilities and the corresponding insect pest that will attack the material. Major insect pests and their associated, diagnostic signs describes the insect pests referred to in Materials, objects, and common damaging insect pests.

UK Plant Health Information Portal
An online hub for plant health information, data and resources

Alternatively, use additional searches based on risk register priorities for actions or try an image based search

About the UK Plant Health Information Portal

Defra recognises the additional challenges being presented to industry as a result of the current COVID-19 outbreak. We aim to support businesses involved in the trade in plants and plant products, to help ease pressure on the food supply chain without compromising the safeguarding of UK biosecurity. We are also contributing to central initiatives, for example, on how Defra can best support the UK’s food supply chain through this period. For guidance and support for businesses and employers, visit

There are many pests and diseases that can seriously damage crops and plants in the UK. Assessing and understanding these threats is essential to informing the actions needed to protect plant health set out in Protecting Plant Health — A Plant Biosecurity Strategy for Great Britain .

As the Strategy makes clear, tackling threats to plant health is not just a matter for government; success is dependent on partnership working between all those with a role to play. To this end the Portal is a shared resource providing information about plant pests and diseases, including the assessments of risk undertaken by government and the data underpinning those assessments, with links to other sites of interest, including non-government sites, as well as information on the plant health controls and services provided by government.

The smarter rules for safer food (SRSF) package is a set of EU regulations for the protection against animal disease, plant pests, and for the organisation and performance of official controls. SRSF brings major changes to the UK plant passport system, and the importing and exporting plants and plant products. The PHR and OCR became applicable on the 14 December 2019. Use the ‘Smarter Rules for Safer Food (SRSF)’ page to find out more.

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