Published on Wednesday, 30 November -0001 00:00
The codling moth has become a serious insect pest of apples in many home orchards. Although this insect has caused damage to apples for many years, it appears to have become a greater pest in recent years. Whether it is because of weather patterns, insecticide resistance, timing of sprays, or some other factor, the population and resulting damage to apples has increased.
Codling moths overwinter as mature larvae in silken cocoons found under loose bark or in debris under the tree. The larvae pupate in the spring and begin to emerge as adult moths during late bloom or petal fall stages of apple development. Female moths lay eggs on developing fruit or nearby leaves. The eggs hatch in one or two weeks, depending on temperature. Once hatched, the larvae begin feeding on the apples.
Larvae bore into the fruit either from the side or the calyx end and begin chewing their way to the core where they feed on the seeds, pushing their waste material, called frass, out of the entrance hole as they advance. Sometimes the larvae will either die or move to another site, forming shallow holes called stings. Either way, the larvae leave unsightly holes that can promote internal rotting. The larvae feed for about three weeks and then exit from the apple and pupate on the trunk or larger branches of the tree. A second generation can occur in late July or August.
A second insect that infests developing apples is the plum curculio. The curculio is a weevil that overwinters as adults in plant debris on the ground. They move to the apple trees and begin laying their eggs about the time the trees bloom. As the female curculios lay their eggs in the apples they create crescent shaped scars on the skin of the apple. The apples retain these scars and when severely attacked the apple itself can become deformed. The larvae feed for about two weeks and exit from fallen apples to pupate in the ground. The adults emerge later in the season and hibernate until the following spring.
Timing is vital to control these apple pests. If coddling moth and plum curculio damage has occurred in previous years, the best way to protect the apples is to spray them with a registered insecticide. Make two applications, the first at petal fall - when about three-fourths of the petals have fallen. Follow with a second application ten days later. Do not apply the spray earlier because it will do no good and it will kill the pollinating bees. Use esfenvalerate, malathion, or a complete fruit or orchard spray that does not contain carbaryl (Sevin). Carbaryl is deadly to bees and at petal fall there will still be bees working in the trees.