Q. Two years ago our cherry tree bore sweet, wonderful cherries, but then I started to see little hole in the cherries. As I was pitting a bowl to freeze, I noticed little worms. Ugh! Last year we were away most of the summer, so I never even examined them, and we let the birds have their fill. Now that a new season is here, I’m looking forward to cherries again. Is there anything I can do to prevent the worms? Will they come back every year? Deborah Anderson – Bonney Lake, WA
A. It sounds to me like that you are describing cherry fruit fly maggots. The dark flies (about 1/5 of an inch) have a white stripe across their abdomen. They lay their eggs under the skin of the fruit in a mode very similar to apple maggot flies. The cherry fruit flies can be distinguished a white band on their abdomen. In answer to your question “will they come back” – my magic eight-ball says: “Signs point to Yes”. Once the flies find your cherries it is likely that they will return each year. This is especially true if you have not been taking measures to control them. The size of each generation can depend on the local populations of predatory insects. The flies are active this time of the year so now is the time (May-June depending on the year) to control them. The braconid wasps are parasitic wasps that control many fruit flies including the cherry fruit fly you are dealing with. Many types of insecticidal sprays can kill of the predators as easily as the prey. The Washington State University extension lists a product called Bull’s Eye Bioinsecticide as a control. This is a product that contains Spinosad, which is biological in origin and is purported to have low toxicity (there still is some toxicity) to non-target organisms including beneficial insects. On smaller trees it is sometimes possible to exclude the flies by covering the tree with a spun polyester cover during the vulnerable stage. But this is often impractical.