As mentioned in Bulletin #12, in early September we discovered larvae in Gravenstein apples
growing on Invermere Court. We recognized right away that these were not codling moth
caterpillars, with which most of us are quite familiar. These damaged apples looked
quite different. There were little ‘sting’ marks on the skin and the larvae had tunneled all through the
flesh of the apples and quite ruined them.
Specimens sent to the Ministry of Agriculture lab at Abbotsford confirmed that the apples
contained larvae and pupae of the Apple Maggot Fly (AMF). This fruit fly has been on
Vancouver Island for several years now and it was probably just a matter of time before it
showed up in Powell River.
So as you are harvesting your apple crops this fall, watch for the Apple Maggot
What is Apple Maggot like?
Apple Maggot Fly is a rhagoletis, relative of Cherry Fruit Fly and Currant Fruit Fly.
• Like them, the fly is about the size of a small house fly with distinctive striped wings.
• It attacks apples, hawthorn, pears, sometimes plums.
• The female fly penetrates the fruit skin to deposit eggs, leaving ‘sting’ scars.
• You don’t readily see the damage until you cut the apple.
• The larvae burrow through the flesh of the apple, making tunnels that go brownish.
• They then begin to pupate in the apple.
• For a time the apple looks fine from the outside although sometimes its surface will start
to get a bit lumpy.
• Eventually it begins to rot and collapse from the inside and eventually falls to the ground
under the tree.
• Then the pupae burrow into the soil and over-winter until next summer – similar to the
CFF and Currant Fruit Fly.
• AMF also generally have just one breeding cycle per season.
• However, flies will keep emerging from the ground all through the fruiting season.
Control methods for Apple Maggot are similar to those used against CFF
and Currant Fly.
- It is difficult to kill the Apple Maggot at the egg, larva or pupa stage. It is the female fly that we have to stop from getting to the fruit and laying eggs
- Put ground cover cloth under the tree to prevent pupae burrowing in during fall, and also to prevent flies emerging in summer.
- If you have chickens, let them run under the trees.
- Cover trees with big nets (‘tree tents’). The mesh does not need to be as fine as for SWD.Such nets can be purchased from Kootenay Covers - www.kootenaycovers.com. Eternal Seeds will order the netting if you place an order.
- It is 7 – 10 days before the emerged female fly matures enough to mate and begin egg laying.This is the time to start to stop them. If you plan on spraying, begin as soon as the first flies are detected/trapped, and then repeat every seven days or so. Google ‘Apple Maggot’ for more details about spraying and also about varying sprays to prevent the flies developing resistance.
- Clean up fallen apples promptly.
- Deal with infested fruit by freezing for several days, baking, boiling, nuking or solarizing.
Apple Maggot is, of course, spread by transporting infested apples, but it can also be
spread in the soil by moving plants from infected areas.
Interestingly, there was a Spartan tree within 50 feet of that infested Gravenstein and its fruit was
nice and clean. We don’t know if this was due to different time of ripening, or different
toughness of skin, or something else. . . However, I have read that the rhagoletis flies do not
travel far if they have a food source, so they might be easier to contain than the SWD if we get
right onto it and use good controls. Hopefully they are not very widespread in Powell River yet.
Please, if anyone else has found Apple Maggot in their fruit, let me know so that we can set out
traps early next summer. We need to know as soon as they appear so that we can alert growers
to spring into action.