Codling Moth

Table of Contents

1. Introduction
2. Description
3. Biology
4. Damage
5. Monitoring and Management

Introduction

The codling moth, Cydia pomonella (Linnaeus), is considered a major pest of apples in Europe, Asia and North America. In Ontario apple orchards it is controlled by normal summer applications of insecticides. However, because of the enormous potential economic impact this pest can have, it is still considered a major pest.Alternate hosts of the codling moth include hawthorn, crabapple, pear, quince, walnut and other Juglans species.

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Description

The larva is a light pink with a brown head and measures 10-12 cm at maturity (Figure 2). It may be confused with the larvae of the Oriental fruit moth (Figure 3) or the European corn borer (Figure 4), which also occasionally attack apple.

Figure 2. Codling moth larva

Figure 3. Oriental fruit moth larva.

Figure 4. European corn borer larva.

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Biology

In Ontario there are two generations of codling moth per year except in the coolest areas (Georgian Bay) where there is only one generation.

The insect overwinters as a late stage (5th instar) larva within a cocoon under bark scales and crevices. The majority of these are located between 30-60 cm off the ground, where snow cover offers insulation. In mid- to late April the larvae pupate inside the cocoon. Adult emergence usually begins in late May or early June depending on temperature.

After mating, female moths will lay up to 20 eggs over a period of about a week. Eggs are laid singly, directly on the fruit, or sometimes on leaves. Eggs take one to three weeks to hatch depending on temperature.

Young larvae immediately seek out a fruitlet where they may feed on the surface for a short time before tunneling into the fruit (Figure 5) to feed on the pulp and seeds. This feeding on seeds is unique and allows codling moth larvae to be distinguished from other "worms" such as oriental fruit moth and European corn borer. The larva develops through five instars before emerging from the fruit and dropping to the orchard floor. Once on the ground, the larva moves to a tree, crawls partway up (geotaxis), and pupates under bark on the trunk or lower scaffolds.

First generation larvae are present in fruit from mid- June to late August. Second generation moths emerge in early August. Mature larvae of the second generation leave fruit as early as late August and well into October.

Figure 5. Codling moth larva, and tunneling in apple.

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Damage

"Stings", caused by the first instar larvae as they enter the fruit, are shallow excavated areas below the skin surface. This injury results in surface blemishes but do not result in any interior breakdown of the fruit's flesh. Deep entries are caused by larvae eating through the flesh as they tunnel toward the core to feed on the seeds. This injury causes internal breakdown of the fruit often leading to premature drop. The exit hole, from which the mature larva emerges is plugged with frass (Figure 6).

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Monitoring and Management

In major apple-producing areas in Ontario, pheromone traps are placed in representative regional sites by OMAF. The traps, consisting of a diamond trap and a pheromone-impregnated lure (Figure 7) are placed into commercial orchards at bloom. Four traps are placed several rows in from the orchard perimeter adjacent to wild hosts or abandoned orchards, preferably downwind of the orchard. The traps are placed at eye level on the north side of the tree and spaced 30 - 50 metres apart. Leaves and branches should be removed from a 30 cm area around each trap. Lures and traps should be changed for each generation and removed in September.

Pheromone traps are monitored twice weekly and male moth trap catches recorded. All counts are inputted into a computer prediction model called Bugwatch. This program predicts critical life stage events such as first egg hatch and peak egg hatch. Information of spray timings is then put on regional agri-phones (or code-a-phones) which growers can access.

Figure 7. Pheromone trap for monitoring codling moth.

Apple growers and consultants are encouraged to place their own traps in orchards, as outlined about and time sprays as follows:

First sustained moth catch is the biofix.

First Spray Date is 100 DDC, base 11°C after Biofix or 50-55 DDC after peak catch (this timing equates to when the first eggs are hatching), roughly 10-14 days after peak catch.

Subsequent sprays may be applied at 14-21 day intervals, based on continued adult trap catches. These "summer sprays" should be timed to coincide with apple maggot activity. An application for second generation codling moth control should be applied in problem orchards at 700 DDC, base 11°C after the first sustained catch of the first flight (Biofix).

Until recently, organophosphates were the only recommended material for codling moth control. However, in the last few years several alternative materials (e.g., the insect growth regulator, Confirm) have been registered in Ontario.

Several strategies for codling moth control exist.

• If plum curculio activity is prolonged into the first codling moth spray (mid- to late June), apple azinphos-methyl (i.e., Guthion, APM, Sniper).
• If plum curculio is not a concern, use either phosmet (Imidan) or tebufenozide (Confirm) for the fist codling moth spray.
• For subsequent "summer sprays" use phosmet (Imidan) which also controls apple maggot.

Following the first insecticide application, usually in mid- to late June, border sprays can be used. Border sprays are pesticide applications applied to the outer 50 metres of orchard perimeter. This distance is usually sufficient to intercept codling moths flying into the orchard from the surrounding environment.

Border sprays are effective only when the following conditions are met:

• orchards are larger than 10 acres
• orchards are square or rectangular, not irregularly shaped
• there is no history of codling moth or apple maggot infestations
• the orchard is not directly adjacent to any abandoned orchard or under heavy pressure from nearby wild hosts
• adequate pesticide coverage over 50 m deep orchard perimeter is attainable (dependent of factors such as canopy density and spray droplet size and velocity).

Additionally, orchards should be well-maintained (e.g., regular annual pruning, balanced fertilizer program etc.)

At the headlands, nozzles on one side of the sprayer should be turned off and the spray blown into the orchard while traveling along the outer edge. Imid-an is the recommended insecticide. Imid-an generally gives 18-21 days of residual - less if frequent, heavy rains occur. Subsequent sprays should be timed for increases in codling moth and apple maggot activity. This information is supplied on local fruit agri-phone updates.

A careful assessment of pest damage to fruit in the orchard should be carried out at or just prior to harvest. If an increase in injury is observed in a given year, a return to cover sprays during the summer months should occur the following season. At that time a reassessment can be done as to whether the problem was rectified and a return to border sprays is possible.

The benefits of border sprays are: they could save hundreds of dollars in spray costs; they allow populations of beneficial insects and mites to build up during the summer months; and the overall environmental impact of pesticides is reduced.

Predators, such as ground beetles (Carabidae), ants and crickets, and parasitic wasps, will attack larvae as the leave fruit and crawl towards tree trunks, but do not give economically acceptable levels of control.

in western North America (Washington, British Columbia), pheromone distribution techniques and sterile male release have been successful in controlling codling moth in apple orchards. These techniques are not feasible or economical in Ontario due to the abundance of wild hosts and the number of other pests that need to be controlled using other methods.

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For more information:
Toll Free: 1-877-424-1300
Local: (519) 826-4047
E-mail: ag.info.omafra@ontario.ca