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Apples bloomed early this year, and the early fruit set may mean that we see
apple maggot flies out earlier than usual. Apple maggot larvae can spoil an
apple completely by munching the flesh into mush. (Those warning signs along
the highways aren’t kidding!) If you have apple trees, mid-May is time
to be sure you have hung traps for the apple maggot fly.
Here's why:
Adults have been spent winter and spring underground in pupal cases (the cases
are 1-2 inches underground.) The flies come out under your trees as weather
warms, often as early as May. (Timing depends on your own microclimate.) They
feed, and then mate. The female fly then lays eggs just under the fruit skin
of growing apples. A female can lay around 300 eggs over a 30-day life span.
(You will notice when you check your trees that the apples are beginning to
form and enlarge. This is what the female apple maggot fly is looking for, a
ripening apple. It doesn't have to be red.)
The little apple maggot larvae, small and tan, hatch in 2 to 20 days depending on temperature. They climb inside the apple or pear (and sometimes plums and peaches), and live inside the fruit, eating and growing, for 20 to 30 days. By the time they stop eating, they have ruined the apples by causing the flesh to deteriorate .
Usually the infested fruit falls to the ground after it's been eaten and the mature maggots leave to burrow into the ground and pupate. This is why the highway signs say "don't transport home grown fruit." If a disgusted eater tosses the apple out, the maggot can hatch and emerge as an adult, thus spreading the infection. They won’t emerge as flies until next year.
What can you do? Watch for the adult flies and hang traps. Apple maggots are a bit smaller than house flies and have pretty markings. They are black and white. The clear wings have the pattern of a stylized letter F as though written with India ink. Would you believe apple maggots are bar coded? The female has four white stripes across the abdomen the male has three.
Now is the time to hang traps: Hang sticky traps in your trees between May 15 and June 1 to trap the adult flies. These are basically flypaper with a scented lure; they attract flies that then get stuck on them.
Trap placement is important. Do not hang traps from the lowest branch! Do hang them up in the outer third of the tree canopy near developing fruit. Clear leaves away from the traps To get best coverage, hang a trap for every 100 fruit. (Another good reason to thin fruit when they are the size of a penny.) Clean insects off the traps with tweezers at least weekly. If you observe lots of AM on any one trap, say 50 flies, hang another trap nearby immediately.
You can make your own traps: Western Cascade Fruit Society has a flyer showing how. Commercial trap supply sources include some local garden centers plus Gemplers 800-382-8473; Great Lakes IMP 517-268-5693, Gardens Alive 812-537-8650 and I.F.M. in Wenatchee 800-332-3179. (No endorsement is implied.)
If you spray, WSU recommends “Surround”, a clay compound that
coats the apples and results in fewer eggs being laid. Use of “Surround”
is described on the WSU
publication eb 1928.
Hortsense: Managing plant problems with Integrated Pest Management
