Last year you had problems with your apples. By the end of the summer, some of them appeared knotty and distorted. When you cut the apples open, you would find brown streaks running through them.
1. What damaged those apples?
This problem is caused by apple maggots. The adult fly is about 1/4 inch long with black and white markings on the wings. When adult maggots lays eggs in apples, they cause the flesh underneath to break which leads to the deformed appearance. As the immature maggots tunnel through apples the areas along these trails decay and turn brown.
2. When should I start to treat my apples for this problem?
Apple maggots overwinter in the soil as pupae but are not active in the spring. They first start to emerge July 1 and are active until the end of the growing season in September. Peak emergence occurs during late July and early August. Apple maggots have a greater tendency to emerge a couple of days after a rain of at least 1/2 inch.
3. Are there any nonchemical solutions to prevent this problem?
You can try trapping them. Place five sticky traps in each average-sized tree (about one trap for every 100 apples). You can buy sticky traps from garden centers or gardening catalogs or make them yourselves. You can also manage apple maggots by placing a plastic bag over the apple. Most kinds of plastic bags will work. Place the bag on the apple you want to protect no later than July 1. Tie or staple the bag loosely around the stem. Cut off the bottom corners of the bag to prevent the build-up of water in the bag.
4. If I want to use an insecticide, how often should I spray?
You can choose between one of several schedules. If you want to use less insecticide, although the results may not be as good, you can monitor adult maggots with a single trap and treat whenever you find more than two apple maggots on it. You can also treat apples two days after a rainfall or irrigation of 1/2 inch or more (do not spray more often than once every 10 to 14 days according to label directions). The most effective way to manage apple maggots is to apply insecticides regularly every 10 to 14 days, starting July 1, although this uses more insecticide than the other methods.
An effective product for apple maggot management is carbaryl (Sevin). Be sure to observe the waiting period between when you spray and the time you can harvest as listed on the label.
