Pests in Chokecherry Trees

Anne,

I have several (four or five) large chokecherry trees that are infested with the Chokecherry Midge. The cherries are swollen and when broken open, reveal a worm and eggs. The chokecherries are ugly and unusable for jelly or syrups (that I particularly enjoy making).

My understanding is that the fly emerges in the spring, from the egg that winters over in the soil under the tree. It flies to the blossoms, attaching itself and turning into a worm that crawls into the cherry. It then feeds on the cherry, lays it's eggs there and dies. The ugly cherries drop to the ground and the cycle starts over.

Am I way off in the woods on this, or what? I can't find any recommended treatment to get rid of this problem, so I pruned one tree back drastically last fall and got rid of the branches loaded with infected cherries. I hope it grows back--it's a sorry sight. Now, spring is coming and I don't want to prune back every tree--I'd like to get some chokecherries again. I've asked a puzzled extension agent--no help there... This problem is new to these trees--two years ago, they were beautiful.

Thanks so much!
Deb


Anne's Response:

Deb,

Chokecherry (Prunus virginiana) is grown commercially in Quebec and northern Ontario and prefers cold weather. The trick to breaking the cycle is to remove all the fruit that falls to the ground and get it off the property. Treat the soil under the tree with an insecticide that is labeled for ground dwelling insects. There are orchard sprays labeled for home use that can be used for insect control when fruit trees are blooming. A major problem with such sprays is that they also kill your pollinating insects. Some directions say to use the spray as the buds swell but before they open and then reapply immediately after pollination. Your insects probably came as visitors from a tree in a neighboring property – often miles away. It could also have been in the soil in the pot if the plants were purchased as potted trees rather than bare root ones.