According to the UGA Extension Viticulture Blog, Japanese beetles are starting to become more widespread in west Georgia vineyards. University of Georgia entomologist Brett Blaauw says the pests are only beginning to emerge but expects the populations to increase exponentially over the next few weeks.
“In large enough numbers, Japanese beetles can be a severe pest of grapes during the summer, feeding mainly on foliage and (thankfully) rarely on the berries,” Blaauw said. “More problematic is Japanese beetles feeding on new plantings. Older, established vines can withstand some feeding damage, but young vines can quickly become defoliated from these beetles. Special attention should be given to newly-planted vineyards.”
As temperatures continue to heat up as we progress throughout the summer, this is ideal weather conditions for beetles to be active. They love warm, sunny days and congregate in groups on vines to feed and mate near the top of the canopy.
There are no thresholds for Japanese beetle leaf damage. However, management is required when feeding damage is below the top trellis wire or about 15% of the leaves are damaged.
“Growers should rely on their judgment and experience to determine whether beetle abundance and/or injury warrants chemical control,” Blaauw said.
For more information, see UGA Extension Viticulture Blog.