If you have an orchard or apple trees on your property, you may have had the unpleasant experience of finding misshaped and disfigured apples instead of the beautiful red or yellow ones you’d dreamed of enjoying. You may have bitten into a lovely apple only to find its flesh laced with brownish grey tunnels. Now is the time to act to prevent the apple maggot (Rhagoletis pomonella) from similarly damaging next year’s crop so you can truly enjoy your apples (or other fruits).
Characteristics & Life Cycle
The apple maggot is a small fly that was originally native to the northeastern United States and Canada, where it fed on hawthorn. Today, it has become a key pest of apples in the Pacific Northwest where insecticide sprays are all too often deemed necessary to produce fruit.
The adult is about the size of a small housefly. The body is black, with dark red eyes, and the thorax and abdomen have white bands. The wings are banded with black. The larvae may grow to a little under ½ inch and are white except for two dark mouth hooks.
The flies emerge from the ground throughout most of the growing season. They feed on organic residues on leaves, such as pollen or honeydew produced by aphids or other insects. After 7 to 10 days, they mate and lay their eggs under the skin of the apples, causing small, brown areas to develop. Each female can lay hundreds of eggs. Eggs hatch within a few days, and larvae begin tunneling through the fruit, leaving a brown, threadlike, irregular trail. The tunnels enlarge as the larvae grow. These tunnels may serve as entry points for decay organisms, which cause internal rotting and interfere with winter storage. Development is completed in 20 to 30 days, at which point the fruit usually drops to the ground. The larvae leave through an opening in the side of the fruit and transform into pupae in the soil, where they spend the winter.
Cleaning up the dropped fruits under your trees at regular intervals is one of the most effective management strategies for home orchards- fall is the time to accomplish this important task! If fruit is left on the ground, maggots will continue to develop in them and then pupate in the soil. The infested fruits are harmless to both people and livestock. They make great treats for cows, goats, and hogs. Or in small quantities, if quartered, for horses. If you live in the city they can be sent to the garbage or municipal compost site. Rurally compost or discard as far as possible from your trees.
Apple maggot traps can be used to reduce fly populations by trapping adults before they reproduce. The traps are red spheres covered with tanglefoot, an adhesive designed to capture insects. A scent lure that smells like apples makes them more attractive. Traps can be purchased or you can make them yourself out of wood, plastic or store bought red apples. Place one to eight traps in each tree, depending on tree size. Clean traps and replace adhesive if needed.
If you only have a few trees, damage can be prevented by bagging individual fruits using plastic or mesh baggies. Beneficial nematodes and kaolin clay have also been found to be useful. Birds, ground beetles, ants and spiders have been observed feeding on maggots but the impact of predation on population control has been discounted. Some organic growers have described that a year of severe infestation may be followed by several years of fewer larvae. Natural botanical pesticides generally break down more quickly and have less toxicity than commercial chemical sprays, however they are still toxic and should only be used as a last resort.
- Planet Natural Resource Center. Apple maggot [Internet]. Undated [cited 2020 Aug 20]. Available from: https://www.planetnatural.com/pest-problem-solver/tree-pests/apple-maggot-control/.