While the warm springtime weather has given bud break a head start and new shoots are growing rapidly throughout most of Sonoma and Mendocino counties, it may not be all good news in area vineyards.
Writing in Western Farm Press, Greg Northcutt points out the warmer weather was also ideal for powdery mildew, which many farmers control with fungicides. Chemical solution may be needed, too, for a new insect pest that’s been spotted in some areas: the Virginia creeper leafhopper, sometimes called the zigzag leafhopper.
Often, the Western grape leafhopper shows up in vineyards late in the season, McGourty notes. Last year growers were seeing a number of leafhoppers at that time and, without looking closely, assumed it was the Western grape leafhopper. Evidently, there were Virginia creeper leafhoppers in the mix…
[O]rganic growers have long relied on natural predators, including the tiny Anagrus spp. wasp that parasitizes leafhopper eggs, to control Western grape leafhoppers. However, Anagrus doesn’t seem to be effective in controlling the Virginia creeper leafhopper.
The article quotes a Glenn McGourty, University of California Extension viticulture advisor, ““Organic growers may not have the biocontrol agents they need to control this pest. Also, conventional growers, who have done a great job of reducing pesticide use in our two counties, may have to start putting on more chemicals to control this particular leafhopper.”
Read the complete article on WesternFarmPress.com.