Apple maggots are annoying, destructive pests for those who grow their own apples. Unfortunately, part of the formula as to whether you'll be successful in controlling these pests is dependent on other factors, such as how many apple maggots are in the area in any given year and how many unmanaged apple trees are around your garden. If you live in an area where others are also growing trees, but they don't maintain them, you may have a tough time on your hands keeping apple maggots under control.
Apple maggots throw a one-two punch when it comes to causing damage to apples. The first damage occurs when they lay eggs on the apples. The apple flesh stops growing at that site, which results in a weird, dimpled or sunken area on the apple—but it doesn't stop there! After the maggots hatch, they tunnel through the flesh of the apple, which causes the flesh to break down and rot. However, with a bit of work and a bit of prevention, you can defeat the destructive apple maggot and have plenty of crisp, perfect apples from your very own garden.
Keep the Area Clean
The first issue to tackle is sanitation. Pick up and dispose of apples within a few days after they've fallen. The best way to dispose of them is to trench compost them—just be sure that your trench or hole is at least a foot deep. If you, like many who grow apples, still want to make use of these fallen apples, you can trim away the bad parts and turn the remainder into cider or applesauce.
The next thing to work on is trapping. The best traps for trapping adult apple maggots are red sticky ball traps. You hang these in the tree, and the adult apple maggots think they're a nice, large apple to lay eggs on—and get stuck to them instead. Use a trap that has a pheromone attractant, which makes even more adult apple maggots attracted to it.
Hang one trap for every 100 apples on your tree, spaced fairly evenly throughout the canopy. For most trees, five traps should do. Be sure to hang your traps as soon as blossoms drop and the tree begins to set fruit. Check the traps regularly to replace pheromones or clean off those that are full of insects and other gunk—the cleaner they are, the better they work.
Bag the Apples
Even if you have unmanaged trees in your area, and it seems like you'll never get rid of the maggots, there is one tried-and-true method of ensuring you get some apples: bagging. If you thin the fruit, then place a plastic bag over each apple when it's small (before the maggots emerge in early summer) they won't be able to lay eggs on them. If they can't lay eggs, then you'll have undamaged apples. Use a zipper-type plastic sandwich bag or any other small bag that you staple or tie around the apple's stem. Poke or cut small holes in the bottom so that any moisture can drain out of the bag. They will need to be bagged all season because the adults are present all season long. The tree may look funny, but at least you'll have perfect apples at harvest time.
Apple Maggots in Home Orchards. University of Minnesota Extension Website