Fig. 19. Codling Moth adult
Photo: Whitney Cranshaw,
Colorado State University, Bugwood.org.
Fig. 20. Codling Moth larva
Photo: Clemson University - USDA Coop. Ext., slide set, Bugwood.org.
Fig. 21. Codling Moth external injury
Photo: Eugene E. Nelson, Bugwood.org
Fig. 22. Codling Moth internal injury
Photo: Clemson University, USDA Coop. Ext., Bugwood.org.
Codling moth is an internal feeder, and infested fruit is not suitable for eating. Codling moth is common in southeastern and central Minnesota, particularly in places where commercial orchards are nearby, and less of a problem farther west and north. If you have never had a codling moth problem in your orchard, then you probably have a minimal population of this pest in your area. If codling moth is common in your area, however, it is very important to manage this pest.
The codling moth larva is large (up to ½” long), and has a pinkish body with a brownish head. Codling moth larvae often tunnel towards the apple cores and feed on the seeds before exiting the fruit. Crumbly golden-brown frass (excrement) is sometimes found at the hole where the larva exited the apple.
There are two generations of codling moth in Minnesota. The first generation adults emerge from their overwintering sites in spring, just before bloom. Mated female moths lay up to 100 eggs on small, developing apples (usually only one egg per fruitlet). After hatching, the larvae chew an opening in the apple’s skin. If they are protected by leaves, they may feed at the surface of the fruit before they tunnel into it.
When they have reached maturity, the larvae exit the fruit, drop to the ground, and crawl away to seek sheltered places to spin cocoons. Some larvae remain in this stage the rest of the summer and through the winter, pupating and emerging the following spring. Other larvae pupate immediately, and emerge as adult moths two to three weeks later, flying to the tree canopy to mate. A second generation that can start in late July or early August overwinters as mature larvae in cocoons in sheltered areas after they drop from the fruit. Typically, in home apple orchards, this second flight is not important.
As with many other pests of apple, sanitation is important in keeping pest pressure low. But because codling moth adults can fly as far as a mile seeking an apple tree in which to mate and lay eggs, you probably will not be able to control this pest by sanitation alone if you live in an area where codling moths are common.
Home growers can reduce codling moth populations by maintaining superior sanitation in their plantings. Pick up and remove any fallen apples throughout the growing season and after harvest and place them in
Sometimes, harvested apples contain codling moth larvae. In storage, the larvae exit the fruit and seek a sheltered place in the storage area. If you store apples in a garage, barn, or other outbuilding, this structure may be a source of codling moth adults the next spring. Wooden apple crates, in particular, provide a good spot for the larvae to overwinter. Inspect your crates and the building in which you store the fruit for silken cocoons, and destroy the insects.
Trapping codling moths
You can trap codling moth males entering your apple planting to determine if codling moths are present. Any number of different insects may find their way into the trap, so you should be able to identify the adult male codling moth. Codling moth adults are medium-sized (about 3/8” long) and light grayish brown. A distinctive band of shiny coppery scales at the rear edges of the males’ wings makes them readily identifiable.
Codling moths are trapped using a tent-shaped plastic or waxed-paper trap, hung in a tree. The most common is the "delta” trap; also used are "wing” traps. The interior of the trap is coated with tanglefoot, and the trap is baited with a small rubbery lure that gives off synthetic female codling moth pheromones (attractant chemicals). Male moths seeking a mate detect the attractant pheromone, fly into the trap, and get stuck in the tanglefoot. See Appendix: sources of IPM supplies, for information about where to buy trapping materials. The trap should be hung at about eye level on the outside of the tree canopy, in early May. Lures typically have a useful life of one or two months. When handling the lure, use a pair of tweezers dedicated to handling codling moth lures, or use disposable gloves. Otherwise, you may transfer attractant pheromone to surfaces other than the inside of the trap.
Check the trap weekly starting in mid-May, to determine if you have codling moths in your area. Clean out the moths and any other insects each time you check the trap.
If you don’t catch any codling moth adults, there probably isn’t a large enough population of this pest to require spraying. In most of Minnesota, the second flight of codling moth is not large enough to require a home grower to spray.
However, if you do trap codling moths, be prepared to treat your apples soon after the first flight has begun. The best timing is to spray at petal fall, i.e. when most or all of the petals have fallen from the apple blossoms. Do not treat before this as the sprays will be ineffective and will also kill pollinating bees. Make a second spray, seven to ten days later (check the label for the exact interval).
Insecticides for codling moth control
Chemicals that control codling moth include esfenvalerate, and malathion. Sprays to control codling moth could coincide with fungicide sprays to control apple scab. In this case, you could mix insecticide and fungicide in the same tank, or use a pre-mixed all-purpose fruit spray that does not contain carbaryl.