Pierce’s disease (PD) is showing up in numerous vineyards on quite a few grape varieties — V. vinifera and hybrids. Vines should be scouted in each vineyard for the three characteristic symptoms of PD: leaf scorch showing marginal chlorosis and necrosis, leafless petioles “match-sticks”, and “green islands” on the canes. In advanced cases, the grapes actually form raisins due to the lack of water supplied to the clusters. Once symptoms confirm the presence of PD, diseased vines should be destroyed as soon as possible. If producers are too busy with harvest to address diseased vines at this time, they should clearly flag the PD vines now for later destruction during the winter. Unfortunately, there are no curative measures for PD, and cutting out symptomatic canes or cordons will not help; half measures will not do, and the whole vine must be destroyed to prevent further spread of Xylella fastidiosa, the bacteria that causes the disease.

Pierce’s disease symptoms on Chambourcin (photo courtesy of Cain Hickey)