Phylloxera on rise…: Deadly insect pest poses increased risk to north coast vineyards

Resistant rootstocks protect grape vines from phylloxera; however, a new form of this insect, Biotype B, threatens the survival of 70% of Napa and Sonoma County vineyards, those which are planted on the rootstock AxR#1. Research demonstrates that different accessions of AxR#l are equally susceptible to damage by this insect, a form of plant lice. The insect has spread from two sites in 1983 to more than 70 sites in those two counties; spread to other grapegrowing counties is likely.