apple worms - Knowledgebase Question

aurora, Co
Avatar for kshoener
Question by kshoener
October 5, 2010
How do I prevent worm infestation in my apples (Gala and Honeycrisp) next spring naturally (we don't want to use pestacides)? We live in Denver, Colorado. Thanks.

Answer from NGA
October 5, 2010
The fruits of apple trees can be ruined by two different types of worms: Coddling Moth larvae and Apple Maggot. Coddling moth larvae are usually found in the core area of the apple. The adult lays eggs inside apple blossoms. When the fruit forms, the egg hatches into a worm-like larvae. Apple Maggot is the immature form of an adult fly. The fly lays eggs just under the skin of the developing apple. When the eggs hatch, the larvae tunnel throughout the flesh of the apple, leaving rust-colored frass (bug poop). When it's time to leave the apple, the larvae digs an exit hole, spins a web, and pupates in the soil below the tree, where it emerges as an adult some months later. Control of both these pests is difficult. There are some pheromone traps (sex attractant) available through mail order companies that you can hang in your trees. Many gardeners have success in trapping Apple Maggots by using red rubber balls, or painting styrofoam balls red, coating either with sticky 'Tanglefoot', and hanging them in the tree. The flies are attracted to the red spheres and try to lay their eggs. They'll be hopelessly stuck if they land. Be sure to pick up and bury any infested or fallen fruit from the tree to prevent a population explosion of either pest. For CODLING MOTH (the worm in the apple): Start preventive spraying of the fruit 7- 21 days after full bloom. Keep the trees protected through August. A third generation can occur from late August to mid-September, so additional protection may be needed through this time. Use Spinosad (Bull?s-eye Bioinsecticide); Monterey Garden Insect Spray; or Kaolin (Surround at Home Crop Protectant from Gardens Alive Inc.) Follow label directions on all products. SPRAY TIMING IS CRITICAL. Follow the spray schedule given on the label. Reapply the spray after a brief, heavy rainfall or showers of longer duration and then resume your regular schedule. If the apple is not protected, the egg laid by the codling moth will hatch and the small worm will enter the apple and be protected from the sprays. If your apples become infested with worms, remove the apples from the tree and seal them in large, black garbage bags. Leave these bags in the sun for two weeks to kill the worms. The traditional approach to protecting apples from apple maggot has been spraying backyard trees with organophosphate insecticides. Since apple maggot spends most of its life cycle protected within the fruit or buried in the soil, the insecticides must be timed to coincide with adult fly activity. Apple maggot flies are active from late June to October. Apply the first insecticide spray within 7 days of trapping the first adult on yellow sticky cards. Repeat applications every 7 to 14 days until preharvest, or more frequently if it rains. It is not necessary to reap-ply an insecticide if no more apple maggot flies are captured on traps after 3 to 4 weeks. Observe the preharvest interval (time interval between last spray application and fruit harvest) on the insecticide label. This interval will prevent unacceptable pesticide residues on your harvested fruit. Best wishes with your apples!

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