Now that apple trees are finishing blooming, it’s time to consider how to handle codling moth and apple maggot so you don’t end up with wormy apples.
Codling moth adults are about 3/4 inch long with mottled gray wings tipped with coppery brown. They start appearing two to three weeks after the tree reaches full bloom. When the moths emerge, they will lay about 50 to 60 eggs on apple tree leaves, branches and fruit. The larvae, which are pinkish white with brown heads, will feed on the tree as they move to the tiny new fruit. They burrow into its core leaving a frass-filled hole on the fruit skin. The larvae feed on the protein rich seeds for three weeks and then leave the fruit to pupate on the tree or ground for two weeks before beginning the cycle again. Here in the Northwest we can get two to three generations a year which makes control necessary throughout the fruit season.
Apple maggot adults resemble a small fly about 1/4 inch long with dark markings on clear wings and a conspicuous white dot where the thorax and the body meet. Female adults begin emerging from the soil around July 1 and lay numerous eggs directly under the apple skin. The larvae hatch and feed on the apple flesh for three to four weeks mining their way through the fruit and creating brown tracks that destroy the apple’s quality. Damaged fruit containing the larvae drop early and the larvae pupates in the soil over the winter.
Reduce the occurrence of these pests by raking up old fruit and leaves in the fall to remove hiding places and over wintering larvae. Put the old apples and leaves in the trash rather than composting them. Apply dormant oil in the late winter to smother larvae.
Because apple maggots lay their egg directly into the fruit, they can’t be controlled by sprays. The females can be attracted to traps that resemble round, red apples but that are coated with a sticky substance (Tanglefoot) that traps the flies. This breaks the life cycle. Fruit can also be individually bagged with pieces of old nylons, paper bags or plastic sandwich bags. Traps and protective covers need to be out by mid-June.
Pheromone traps can help detect the presence of codling moths. The traps are sticky pieces of cardboard baited with the scent of the female moth. The male moths, thinking they have found their true love, get stuck on the trap. Check the traps every couple of days for the presence of moths. If the moths are present so are their larvae. Once they are present, begin a regular spray program every 10 days. This offsets their life cycle.
Malathion is the conventional spray for codling moth. A relatively new organic control is spinosad, a soil bacteria-based spray that is OMRI listed for use in organic production. The larvae ingest the bacteria and it kills them internally.