Codling Moth

Codling Moth (Cydia pomonella)

Hosts

Apple, crabapple and pear; rarely other fruit trees in B.C.

Damage

Surface ‘stings’ or holes in fruit plugged with dark masses of excreta; both types of damage allow fungi and bacteria to enter the fruit and cause fruit rot during storage.

Codling moth damage Codling moth damage to apple

codling moth entry hole Codling moth larval entry hole (sting)

Codling moth damage Codling moth larval entries (stings) on apple
Photo courtesy Agriculture & Agri-Food Canada

Identification

Larva - Pinkish-white caterpillar with black or mottled black head; mature larvae 12-20 mm long.
Adult - Brownish-gray moth about 10-12 mm long with a copper spot on the end of each forewing.

Codling moth larva Codling moth larva in fruit

Life History

Mature codling moth larvae overwinter in silken cocoons in protected sites on the tree (under loose bark, in cracks and crevices), in the soil or in wooden materials under or beside infested trees (bins, ladders, poles, buildings, large prunings). Larvae pupate in the spring and adults usually begin to emerge in early May and continue emerging until late June (mid-July in cooler areas), depending on temperature. Mating and egg-laying occur when twilight temperatures are above15°C. Females lay eggs on fruit or on leaves near fruit. Larvae usually wander over the fruit surface before cutting through the skin and boring deeply into the fruit. Mature larvae leave the fruit to pupate in protected sites on and off the tree as described above. Second generation moths appear in late July and August. Because weather during July and August is usually favourable for codling moth activity and reproduction, second-generation larvae can cause considerable damage, often close to harvest. If weather is warm during late August or early September a partial third generation may occur in southern districts.

Monitoring

Use codling moth sex pheromone traps in all apple and pear blocks to estimate population levels and determine the need for sprays. The fact sheet Codling Moth Sex Pheromone Traps, which is available from the Kelowna BCMAL office, provides details on installation, placement, maintenance and use of traps, and assists in the interpretation of trap captures. Install the traps in orchards by the pink bud stage and serviced weekly to record the location and the number of male moths captured. Replace the lures every 5-6 weeks and change the trap bottoms when the stickiness diminishes. Each trap will monitor approximately 1 hectare of orchard. Orchards less than 1 hectare or with mixed fruit types or very irregular borders are difficult to monitor with pheromone traps.

After a spray is applied, service the traps as usual to provide the information needed for decisions on additional sprays. Continue to monitor trap catches until 2 weeks before harvest.

Timing of the first codling moth spray in the spring can be more accurate if the beginning of egg hatch is predicted using codling moth trap captures and degree-day accumulations. The pamphlet Predicting Codling Moth Spray Dates with Degree-Days, which is also available from the Kelowna BCMAL office, explains how to measure temperatures, determine biofix and calculate degree-days necessary to time the first spray. A maximum-minimum thermometer housed in a well-ventilated shelter is required in order to record minimum and maximum temperatures necessary to calculate degree-days.

Control

Banding - To detect and reduce larval emergence, corrugated cardboard bands should be applied to tree trunks and scaffold limbs by mid-June through to the end of July. This encourages any larvae leaving the fruit to enter the cardboard bands and spin cocoons. Replace the bands applied for the first generation larvae at 7-10 day intervals and burn used bands immediately after removal to prevent larvae from completing their development and exiting. Banding for second-generation larvae should commence in early August. Remove and destroy these bands after harvest. In warm years with a 3rd generation, remove the summer bands at regular intervals to prevent development. Banding material is available from chemical suppliers.

Fruit Removal - It is extremely important that fruit found infested with codling moth is not left on the trees at any time during the growing season. Growers should make sure that infested fruit found while thinning and picking is destroyed, in order to kill any larvae in the fruit; complete crushing of fruit is the best way to kill larvae. Culled fruit should never be dumped in orchards. If infested fruit is placed in water to drown the larvae, do not remove the apple for at least one week.

Sanitation – Remove any non-commercial codling moth host trees; if on surrounding properties or public lands, brought to the attention of SIR staff. Woodpiles and any wooden structures, such as fruit bins or boxes, tree props, or ladders, are important sources of overwintered codling moths. As codling moth populations decrease, it becomes important to eliminate or treat wooden structures within or immediately adjacent to the orchards. Pay attention to the source of anything wooden entering the orchard, especially wooden bins and props.

Mating Disruption - Mating disruption works by preventing male moths from finding female moths for mating within blocks treated with the pheromone dispensers, Isomate-C Plus (codling moth) or Isomate CM/LR (codling moth and leafrollers). This control tactic is most effective when applied on an area-wide basis involving as many adjoining orchards as possible. Dispensers should be applied at a rate of 1000/ha (400/ac) before the first moths fly in the spring. Do not reduce the rate before consulting with the SIR program or your crop management advisor. Place the dispensers in the upper third of the canopy, preferably in shaded areas, by wrapping each dispenser once loosely around a twig. Apply a first cover spray if codling moth damage was greater than 2% the previous year. Orchards less than 2 ha in size are not suitable for mating disruption. Growers should apply a border cover spray along edges adjacent to unmanaged sources of codling moth. Place additional dispensers in border trees to minimize the effect of immigration. Carefully read and follow the instructions provided with the dispensers.

Biological - Virosoft CP4 Granulovirus – Codling moth larvae must eat the virus before they enter the fruit, so thorough coverage is essential. The efficacy of the virus deteriorates quickly (short residual period). Apply weekly in the late afternoon or on a cloudy day throughout the period when codling moth larvae are emerging from eggs. Because the granulovirus does not kill codling moth larvae as quickly as most chemical sprays, some feeding damage will occur. Store Virosoft in a cool place between uses to reduce degradation of the granulovirus.

Chemical - Only apply cover sprays in those areas of the orchard where trap captures have averaged 1-2 or more moths per trap per week over 2 consecutive weeks. Use a lower threshold of 1 moth/trap for 2 consecutive weeks for Golden Delicious and high-value apple varieties.

By using degree-day predictions to time the first spray, forecasting dates of codling moth egg hatch is more accurate and spraying can occur when the control products can perform most effectively. The optimum timing varies among the products recommended for codling moth control. Apply Diazinon, Guthion/ Sniper, Imidan and Zolone when the degree-day total predicts that egg hatch is beginning (about 250-300 degree-days). Apply Assail, Confirm (maximum 4 applications per season for all uses) or Intrepid (maximum 2 applications per season for all uses) during egg laying (starting around 200 degree days) as these products kill eggs and newly hatched larvae. Reapply not less than 10-14 days later if required. Information on the approximate time of egg hatch for first brood is available from most packinghouse field service offices and the SIR offices. Use temperatures collected at your own site to achieve the most accurate spray timing.

Apply additional first brood and second brood sprays only after pheromone trap captures reach treatment levels and the residual protection from sprays ends. Under low-rainfall conditions, Guthion/ Sniper provides about 3 weeks protection from codling moth damage; Assail, Confirm, Intrepid, Zolone and Imidan provide about 10-14 days protection. Larvae must eat Assail, Confirm and Intrepid to be most effective so thorough coverage is essential.

Research shows that Assail and Admire may increase egg production in mites. Therefore do not apply more than two applications of Assail or Admire either alone or alternately per season regardless of target pest (codling moth, aphids, leafhoppers, leafminers) to avoid mite flare-up. If Sevin is used as a thinning spray in the same block treated with Assail and/or Admire, consider monitoring mite levels.

Pesticide resistance management - It is important to alternate application of insecticides from different chemical families or with different modes of action in order to avoid development of pesticide resistance.

For more information on codling moth control programs visit the Okanagan-Kootenay Sterile Insect Release Program.

March 2006

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