Diseass risks from May 6-9th

Well, it looks like finally we have some break from rains.

In Winchester area, rain started around 9AM on the 6th, and although there were a few interruptions, relative humidity stayed above 90% most of the time until around 9AM this morning (the 9th). Temperature varied from upper 40’s to low 60’s and most of time, it was low 50’s. This rain event was long enough for Phomopsis and black rot infection events.

A few people asked me “What should I do now?”

Well, it depends on when you have sprayed last, and also, what type of history of black rot you had in the past. If you missed the spray before the rain (i.e., your last spray was more than 10-14 days ago), and your vineyards had an issue with black rot (which is not a common), it may be a good idea to consider either a DMI (SI) or a QoI (Strobilurins). We want to keep DMI for later use, so, unless you know for sure that the rain from the past few days will give you an issue with black rot, my recommendation is a use of a QoI, such as Abound, Flint, etc.  Since we still have some time to monitor until bloom, if you prefer not using DMI or QoI, and want to watch for a while, I think that is an option too.

If you missed the spray, but have not seem much issue with black rot in the past, I probably just stick with mancozeb, and see how things go.

Either way, the risk of black rot may become high due to this rain event, please make sure to scout the vineyards!  It takes about two weeks for black rot to produce symptoms.

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