Virginia Grape Disease Updates

Today is the one of the days when you find many things in the vineyard!  Mealybugs (white one in the middle of the picture) are also observed, mainly at the base of the shoot (or a spur in this case).  You also see a scale insect on this picture.  Please note that both mealybugs and scale insects can transmit several virus pathogens, including the ones cause grapevine leafroll disease .   Unfortunately, once the vine is infected, only remedy is removal of the infected vine.  (However, please note that the presence of leaf roll virus does not always results in immediate loss of crop.)  If you have both mealybugs and virus infected vines, and have a plan of expansion, it is probably a good idea to protect new vines using insecticides.  However, you have to make sure you have both the virus and mealybugs to justify your action since insecticides for mealybugs are relatively expensive, and as with other chemicals, application of unnecessary insecti...

Rain from yesterday (4/2/12) started around 9PM on 4/1, and lasted until 2:30AM or so.  The RH was high (>90%) until 3:55AM, thus this was about 7 hours of wetness period with an average temperature of 55F.  That was Phomopsis infection event. Our 4th year Chardonnay is about 1.5 inch growth (3rd and 4th leaf visible); however, there are noticeable differences among vines.  Some are almost 100% bud break with a significant growth and the others are less than 10% bud break with very minimal growth.

I've been in and out of my office with my leaf roll survey project, and it has been bit difficult to frequently update the blog. Also, at this point, not much you can do about major fungal diseases. The critical time of infection is gone. If you see downy, powdery, or black rot on your bunches, the infection probably took weeks ago, if it was not a month. Thus, I will point some key issues at this time of the year. Botrytis, downy, and other rot We had a long period of wet and cool nights during the last half of August. This conditions favors both Botrytis and Downy mildew sporulation, and potential infection on nearby leaves. (i.e., it won't spready quicky, but it probably enough to increase number of spores.) If it is followed by rain (like we had last week), the risks of Botrytis and downy mildew increase. As I mentioned earlier, downy mildew won't touch berries at this point. Berries are resistant to the infection. However, with a prolonged rain or high hu...