Codling moth
Click for larger image Codling moth larva or caterpillar (Lepidoptera) inside an apple (Malus domestica). Clemson U - USDA CES Slide Series, Bugwood.org

The codling moth, Cydia pomonella, is a serious pest on apples, but it can also do damage to pears, plums, quinces, and walnuts. Injury to apples is caused by the codling moth larvae, which tunnel into the fruit, usually to the core. Damage is restricted to the fruit; the larvae do not cause damage to other parts of the tree.

Symptoms and Diagnosis

Larval feeding damage is either "stings" on the fruit skin or tunnelling within the fruit. A "sting" is the result of a larvae taking one or two bites of the fruit which causes a surface blemish. If the larva continues to feed at one site, a deep entry or tunnel will be the result. The tunnel openings are surrounded by the crumbly, brown fecal matter of the codling moth larvae. The feeding damage causes fruit to rot and drop prematurely, reducing yields.

Life Cycle

The adult moth is a small gray-brown moth with pale, fringed hind wings. Their wingspan measures only 3/4 inch wide. Larvae, when fully developed, are 1 inch long worms with pinkish or whitish bodies and dark heads. Only fully grown larvae overwinter. Larval or pupal stages overwinter in a thick, silken cocoon under the bark of trees. Adult moths first emerge from the cocoons in the spring, when apple trees are in bloom. Females lay eggs during flower bloom. Young larvae tunneling through the developing fruits feed and emerge to pupate under the tree's bark. After the larvae pupate, a new generation of codling moths emerges in the midsummer. In Missouri, three generations occur every year.

Integrated Pest Management Strategies

1. Monitor for codling moth. Hang sticky apples prior to petal fall. As soon as moths appear, begin your control strategies.

2. Tie paper bags around the developing fruit. This technique will protect the fruit from pests. This technique is feasible only for low numbers of trees or fruit. This should be done in early May or June, after pruning.

3. Trap mature larvae before they can pupate with a band of Tanglefoot painted around the bottom of the tree trunks.

4. Spray trees with Bt (Bacillus thuringiensis) later on in the season to kill larvae. Repeat at 7–10 day intervals until larvae stop emerging.

5. Apply horticultural oils before the buds begin to open in the spring. This treatment will suffocate the pupating larvae if the entire tree is sprayed.

6. Apply insecticides. Pesticides registered for use include carbaryl (Sevin), cyfluthrinpermethrin and spinosad. Apply as soon as adults appear. Make 2-3 applications, 3-5 days apart.

Organic Strategies

Strategies 1, 2, and 3 are strictly organic approaches. For an organic approach to Strategies 4 and 6, consult the Organic Materials Review Institute (OMRI™) for appropriate Bacillus thuringiensis (Bt) and spinosad products.

More images:

Click for larger image
Adult codling moth (Lepidoptera). Clemson U - USDA CES Slide Series, Bugwood.org
Click for larger image
Damage inside an apple (Malus domestica) from the tunneling of a codling moth larva or caterpillar (Lepidoptera). Clemson U - USDA CES Slide Series, Bugwood.org