Grapes - rose chafers
This question came into our office: They planted a few dozen grape vines a couple years ago. Last spring they were full of little grape clusters. Since they don't live on the property, they came back up about 2 weeks later to discover the grapes were gone and the vines were covered with bugs. They did an online search and found out they were rose chafers. The website said if they had more than 2 per vine, it was an infestation; they had about 2 per leaf and had hundreds of bugs on each row. They said that some sites said the traps were the way to go; others said the traps brought more in. They want to know, "What spray should they use that won't hurt their grapes but gets rid of the bugs?"
Kalkaska County Michigan
Traps for rose chafers will not work when the numbers are high - even at low populations they sometimes fail, because more beetles are attracted to the traps then the traps can hold-- the excess beetles end up on the grapes (or whatever).
Many pesticides work well against rose chafer for short periods of time - no matter what you use (that's legal) it will need to be applied often during the peak of beetle activity- possibly every other day for weaker materials. Synthetics: Sevin is still the best; pyrethroids usually work well. Organic: rotenone, pyrethrins are probably best. Folow label directions- some do not allow frequent applications at short intervals. Under moderate populations, spray only clusters, as the leaf injury is tolerated fairly well by grapes. Higher populations may require treating leaves as well. Rose chafer season is short, so at least you won't have to keep up with the spraying routine for much more than 2-3 weeks.