As I have reported over the last 2-3 years, we are observing warming winter temperatures, and as a result, we are also observing increasing levels of Pierce’s disease (PD). With colder winter temperatures, the bacteria that causes PD, Xylella fastidiosa, can actually be “cured” from the vine. With warmer temperatures, the bacteria survives and kills infected plants. In the past, elevations of ~2000 feet or greater did not provide conditions that were conducive to PD development. Unfortunately, that is no longer the case. Numerous vines with PD have now been confirmed by county agents at elevations of ~2000 feet. It is a bit late to start scouting for PD, and leaves will soon change color and start to abscise. However, I would still scout at this time for vines that might be showing signs of Pierce’s disease. These should be marked for destruction, as this is one of the primary means of slowing the spread of disease in a vineyard — roguing symptomatic plants. Clark McAllister and Nathan Eason, county agents in Lumpkin and White Counties, can test for the disease in petioles from suspect vines. This confirmation can give you peace of mind, as you would hate to destroy vines that do not have PD. For additional information on the disease, see the fact sheet below. PD identification can sometimes be a bit tricky in the field, so ask for help if you are not comfortable with identifying symptomatic vines on your own. If you have questions concerning this disease or others, contact your local county agent for additional information.
