Field observations show that the degree of susceptibility can vary by cultivar.
However, these differences are slight to nil for vines less than 3 years old. Unfortunately, the most resistant wine cultivars are among the least in demand commercially. Conventional plant breeding . Many grape species grow where pressure from PD is high and where GWSS and other insect vectors are abundant. UC Davis plant geneticists have a long-term breeding program under way to identify the X. fastidiosa resistance genes in these grape species.