The Q&A Archives: Beetles eating grapevine

Question: I have a young grapevine that was decimated last year by thin, brown beetles eating its leaves. What are these bugs and how do I control them? Dell Mayse Gorham, ME

Answer: The culprit is the rose chafer, says Dave Handley, vegetable crops and small fruits specialist at the University of Maine's Highmoor Farm in Monmouth. The thin, 1/2 inch long, tan colored adult beetles are very similar to the Japanese beetle in lifecycle and in their taste for the leaves of grapes, roses and raspberries, as well as those of many other fruits and flowers, he explains. Usually the larvae live in the soil for two to three years, feeding on plant roots, until they grow large enoughto emerge as adult beetles. In your area, however, the soil generally gets too cold for rose chafers to overwinter. Most of your problems are due to adults that fly up from the South, says Handley. We first see them when the wild roses bloom late June in our area, he says. Although the chafers are most noticeable in early summer, they feed until fall, then mate and lay eggs in sandy loam soil. Adult chafers can quickly decimate a plant, but their numbers and the degree of damage fluctuate from year to year. The best control for small plantings is to handpick adults as soon as you notice them and to drown them in a can of soapy water, says Handley. Grapes can survive defoliation as long as not more than 20% of the grapevine is defoliated for two to three years in a row, he adds.

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