In the past several years there have been an increasing number of these insects damaging our precious cherries! Treatment has to be done weeks ahead of time to stop the damage otherwise the insecticide will not be able to reach the worms inside the fruit.
What is it?
Western Cherry Fruit Fly
What does it do?
In May, as the cherries begin to turn color the flies begin mating and laying their eggs. These eggs are inserted and deposited inside ripening fruit leaving very little evidence of the fact. That is why when we go to pick and eat the cherries there are worms inside!
What do I do?
For the homeowner, monitoring and spraying is the simplest thing to do. As soon as cherries begin to color, put out Pest Wizard Deciduous Fruit Fly traps to monitor when the flies are present. This step can be eliminated and you can just begin spraying as the fruit begins to color but I always spray (even organic sprays) as little as possible so you can wait until you find adult flies to reduce the number of applications.
There are a few different things you can spray but I recommend Monterey Garden Insect Spray. The active ingredient, Spinosad is not as toxic as Malathion or Sevin yet effective on certain insects. It is also OMRI listed! Begin spraying as soon as you see the adult flies on the traps or as the cherry begin to turn color. Spray once per week until harvest.
So it is simple, just a matter of being prepared. Hope this helps!
Happy Cherry Season!
P.S. If you would like to read further about the Western Cherry Fruit Fly, here is a good article.