Codling Moth

Host Plants

Apples, pears, walnut, quince

Regions impacted

Found throughout North America and generally wherever apples are grown throughout the temperate regions of the world.

Description

The codling moth is a tree fruit pest that belongs to the family Tortricidae, one of the largest families of moths. These moths are small, usually gray or brown, with banded or mottled wings spanning ¾ to one inch. The larvae, at about an inch long, are pink or creamy white caterpillars with brown heads.

Life Cycle

• The codling moth winters as a mature larva in a cocoon; they begin changing into pupae early in the spring, prior to the opening of blossoms. Adult moths begin to emerge when apple trees bloom and will continue to emerge for 6 or 7 weeks.
• Moths mate and begin laying eggs within a day of emerging. First-generation eggs are laid primarily on leaves, although some may be found on fruit and twigs.
• Eggs require 8 to 14 days to incubate, and the newly hatched larvae burrow into the fruit core, usually from the blossom end. As they feed, they push excrement out of the apple through an entry hole, which is gradually enlarged and often serves as an exit hole.
• Larvae are fully grown in three to four weeks, at which time they leave the fruit in search of sheltered places, such as under bark or in the ground litter, to spin cocoons.
• There can be two to three generations of codling moth per season, 5 to 8 weeks apart.

Damage and Detection

• Codling moth larvae bore deep into the fruit to feed; if uncontrolled, codling moths can destroy most of the crop. Although codling moths prefer apples, they also attack pear, apricot, cherry, peach, and plum trees. In California, certain races of codling moth also attack prune and walnut.
• Damage inflicted by larvae can take the form of stings, or “shallow entries”, and more damaging, “deep entries”.
• In stings, the larva burrows into the flesh to feed but either moves on or dies.
• In deep entries, the larva proceeds through the fruit’s flesh to the center of the fruit, where it then continues to feed on the seeds.
• Both types of damage make fruit unmarketable, but deep entries have a higher potential for crop damage, given the formation of bacteria and fungi associated with the deep entry damage.
• Larvae can be found under loose bark, in the litter at the base of the tree, and in wood piles or picking bins.
• The caterpillar’s exit hole is often visible on the side of the ripe fruit or at the ‘eye’ end, When the fruit is cut open, the tunnel and feeding damage inside the core can be seen, together with the caterpillar’s excrement pellets.

Prevention and Control

• Scrape off areas of loose bark in early spring to remove overwintering cocoons as a general maintenance matter.
• Pesticide treatment is only possible and worthwhile on small trees that can be sprayed thoroughly. Spraying around the third week of June, with a second application about three weeks, may have some effect. Plants in flowers should not be sprayed due to the danger to bees and other pollinating insects.
• Encourage predators and other natural enemies in the garden, such as birds and ground beetles.
• Consider growing cover crops to attract native parasites and predators, and other natural enemies in the garden especially ground beetles that eat pupae.
• Pheromone traps can be used to trap male moths. They are available from garden centers and consist of an open-sided box hung in the tree in early May. These traps alone rarely control codling moth activity but can assist in catching enough males to reduce the females’ mating success. Hang one codling moth trap per dwarf tree (up to four traps per large tree) and maintain it according to the manufacturer’s instructions. By counting the trapped males every week and following the instructions that come with the trap, the best time to spray can be determined.
• Cover fruits with nylon barriers before they reach a 1-inch diameter.
• Check trees weekly as a routine matter, and remove and destroy any infested fruit.