The total hours of wetness was about 18h with the average temperature at 50-56F. It was long and warm enough for both Phomopsis and black rot. Also, these spring rains will help powdery mildew spores (ascospores that are from winter survival) to be disseminated to the air.
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
Hi, Great info here but as wondering if you could also post prior to an event with your recommendations based on the forecast.
ReplyDeleteHi, Good question. A short answer is "We are working on it." ;)
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