Rose Chafer Infestation
We recently bought a home that included 32 fruit trees, asparagus, raspberries, and blueberries. We are currently dealing with an infestation of Rose Chafers. They are wreaking havoc on the fruit trees - especially the cherry trees. Pulling them off one by one is not an option - too many. I'm not particularly interested in pesticides, but I'm not ruling it out at this point. Do I just let them run their course and accept the damage? Is there something preventative I can do next year? If I were to use a pesticide, which one should I use and how should I use it?
Grand Traverse County Michigan
Most healthy and well-established plants can tolerate the damage from rose chafers event though it can make them look pretty ragged in an outbreak year. Smaller plants such as vegetables can be protected with a floating row cover. The chafers are only active for a few weeks, and the covers can be removed afterwards. If you can identify an area of your yard where the females seem to be laying their eggs, then you could consider treating that area with beneficial nematodes (also know as Entompathogenic Nematodes). The nematode species Heterorhabditis bacteriophora is effective agains grubs in the soil, which includes the immature stage of the Rose Chafer. However, because this insect is so mobile, treating your yard for them may not have much of an impact on the number that fly in from elsewhere.