Although it’s been a rather atypical year for disease pressure, there are a few problems showing up in vineyards around the state.

“It seems that powdery mildew is light in most areas, but a problem in southern San Joaquin Valley and the coast,” says Doug Gubler, UC plant pathologist. “There hasn’t been much Botrytis. However, canker diseases on grapes are severe this year, and esca/grape measles is rearing its head. Canker diseases seem to be active statewide.”

According to Gubler, most of the canker diseases occurring this season seem to be caused by Botryosphaeria spp.

Esca/grape measles is more prevalent in areas with consistently high summer temperatures, such as the central San Joaquin Valley. Heavy spring rainfall also favors disease development, although that runs counter to what transpired earlier this season.