August and September are the best months for testing. In California the grape sharpshooter and spittlebug are known to vector PD from host plants to grape vines. Every effort must be made to monitor these pests and control them as they occur. In California these insects are also monitored in the native vegetation adjacent to the vineyards and controlled there before they enter the vineyard. Line drawings of leafhoppers and sharpshooters are enclosed.
Spittle bugs produce a white cotton like substance on the leaves.
Additional information will be forward to you as it develops. For additional information on PD, please do not hesitate to contact me.