Seattle Tree Fruit Society

Fig 1. Adult maggot flies

What are apple maggots?

Adult female apple maggots are small fruit flies (about ¼ inch long) that lay their eggs just below the skin of apples. They can attack immature fruit starting in June or July and successive flights can continue laying eggs into the fall. The eggs hatch within a few days as larvae.

 

Fig 2. Interior damage

What happens to the infected apple?

While the larvae lack legs, they are prolific tunnelers and will proceed to lay tracks throughout the flesh of the apple. While in some cases you can see the tiny entry wound or the skin will reveal the presence of an infestation, often you won’t know until you cut the apple open after harvest! In most cases, the infected apple is useless.

Fig 3. Exterior damage

What non-chemical control measures are available?

Over the years various ideas have been tried. One is to hang colored sticky traps (yellow sheets or red balls) in the trees with an attractant designed to lure the fly. These may be useful to monitor the presence of maggot flies but are usually ineffective in controlling apple damage. Other approaches involve protecting the apple with a physical barrier. One is to apply a kaolin clay covering but these require re-application (every week or 2) until harvest. Some folks have had luck with paper or plastic bags.

Fig 4. Maggot barrier on apple

Maggot Barriers to the rescue!

Several years ago Seattle Tree Fruit members started experimenting with small nylon sleeves that are applied when the apple is between a dime and a quarter in diameter. A good time to do this is when you thin the tree in May or early June. Once applied the nylon stretches as the apple matures and stays on the apple until harvest. In our experience, the Barriers have proven effective in significantly limiting the damage from the apple maggot larvae.

Maggot Barrier Order Form