We had a short shower event last evening; however, it was short and relative humidity did not stay high for a long time. Thus, it was not a major disease infection event, except, probably downy mildew, since it only take about 90 min under optimal condition. Speaking of downy mildew, we have seen the beginnings of downy mildew in our experimental vineyard. Although our last application of mancozeb was only 10 days ago, rain events and humid nights probably promoted their development. At the beginning, you will see yellow circular discoloration on upper surface of the leaf. Please note that sometimes insect can cause similar symptoms. However, if you flip over, you will see tiny white growth (please click the picture to access to a higher resolution file). This won't happen with an insect damage. Please scout your vineyard, and if you see similar symptoms, it is probably a good idea to incorporate some of fungicides with kick-back activity. In fact, we ...