Saturday, June 9, 2018

Watch for Codling Moths on Apple and Pear Trees

Adult Codling Moth, photo courtesy CSU Extension
For the first time in several years, we didn't have a late spring freeze in 2018! That's good news for fruit production in Jefferson County. The fruit trees are already showing signs of a banner fruit yield. Watch your apple and pear trees for codling moth - it's the most important insect pest of these trees in North America.  Damage is done by the larvae, which are cream-colored caterpillars that tunnel fruit and produce ‘wormy’ apples.

Small entry wound indicates infestation by a developing codling moth caterpillar, photo CSU Extension
Here are some quick facts about the codling moth:
  • The caterpillar of the codling moth is the common ‘worm’ in a wormy apple or pear.
  • Most injury is usually produced by the second generation, which begins in early summer.
  • Non-chemical controls that can reduce fruit damage include fruit thinning, prompt removal of infested fruit, bagging of fruit and the use of certain traps.
  • Insecticides are useful when applied to coincide with periods when eggs are being laid and before the newly hatched caterpillars borer into fruit.
  • Pheromone traps can be useful in timing sprays.
Codling moth larvae can enter fruit at any point on the surface of apples but often attack at areas that provide some cover such as the stem end, calyx end, or where two fruit touch. Larval entry into pears, which are harder-skinned, is primarily at the calyx end and attacks of pear occur later in the growing season. Rarely, codling moth larvae have been found in cherries, peaches and large-fruited crab apples. Although control of codling moth in these trees is not necessary, infestations in crab apples can be significant sources of codling moth that may later migrate to nearby apple and pear trees.

Although the caterpillars tunnel through the flesh, most feeding is concentrated on the developing seeds of the core. When full-grown they again tunnel out of the fruit, creating larger wounds. Brown excrement (ick!) is piled around the entry point and where they exit the fruit. 

Codling moth spends winter as a full-grown caterpillar within a silken cocoon, pupating in late winter or early spring. Adult codling moths first emerge in spring, typically within days of apple bloom. Earlier emergence may occur if the insects spent wintering next to a building or other warm area. Peak emergence can occur within a week of the first moth emergence, but the last moth of the first generation may not emerge for six or seven weeks. Mating occurs within a few days of adult emergence followed by egg laying. Egg laying increases as night time temperatures increase above 62°F.

Successful management of codling moth is dependent upon many factors such as size and extent of the codling moth population, number, size and condition of trees, presence of natural enemies, available pesticides, and tree owner attitudes. There is no one-size-fits-all best management strategy for all homeowners wishing to manage codling moth. 

For more information on codling moth habits, natural and cultural controls, mating disruption, trapping and sprays, read CSU Extension's Fact Sheet: Codling Moth: Control in Home Plantings.