In Winchester area, rains from May 22-23 resulted in ~19 hours of wetness with an average temperature in lower 60's. We had 5-6 hours of dry period, then another rains went through the area, starting around 5PM last night. Relative humidity remained high (>90%) until around 5AM this morning, thus it was about 12 hours of wetness. Average temperature was again in low 60F. Both were infection events for Phomopsis and black rot. A total precipitation of the last three days was about 0.7 inches.
Also, in the last few days, night time temperatures were warm (in 60's) and relative humidity were high, thus, these could be downy mildew sporulation events as well.
At Winchester, we had light rain events during the night of 6/12/09, but it was short events and the relative humidity was low (80% or so), thus it probably did not promote any infections. However, we are experiencing continuing favorable nights for downy mildew sporulation (average T>55F, high RH (80-100%)) for 10 days now. Yesterday, we conducted a formal disease assessment, and observed first incidence of powdery mildew for this season. We had plenty of infection events in last two months, so it was not surprising. At this point, it is a trace level of infection on untreated vines. Downy mildew was the major disease so far. We had up to 40% incidence on untreated vines. Next runner-up was black rot. It varies vine to vine, but some of vine had 10-15% incidence. Phomopsis was omnipresent as I expected from early May rain falls, but severity was low overall. We will examine diseases again in the near future, and I will update as the season goes. Here is downy mildew ga...
Comments
Post a Comment
Please leave your comment here. In order to avoid spam messages, l moderate comments, thus it may take a few hours for your comment to be posted on the page.