More on Phomopsis and other disease concerns

Well, it looks like we will see more rains coming in next week or so. Sounds like a typical start of the season for VA vineyards, doesn't it?

Since most of vines have 2-10 inches of shoots, our main focus will still be Phomopsis, especially if your vineyard(s) experienced Phomopsis in the past.  At Winchester, we are experiencing 27+ hours of wetness with the average temperature of 48F or so. This will be a low Phomopsis risk event, and counting.

Plus, especially if you had a serious downy mildew issue in the past season, it may not be a bad idea to think about downy mildew because the next series of rains for this weekend and early next week may happen when air temperatures will be in 60's and 70's.  As for Phomopsis, a protective spray of mancozeb, captan, etc. is pretty much the only mean of management, but we do have some options for downy after the rain event.

So, if you did not spray before this series of rains, but you are lucky enough to have a window for a spray before the big rain on Sunday, you may want to go ahead with it. I would go with mancozeb (if your aim is Phomopsis alone) or add a phosphite (Prophyt, Phostrol, etc.) to the mix, if you have a reason to believe downy could be an issue at your location. Also, trial reports from Michigan State showed that a phosphite would work against Phomopsis too. (I am not sure that it can have a kick-back activity, though)

If you won't have a chance before Sunday, or you have applied before this week's rains, then I would add a phosphite to the next mix of your fungicide application. As I mentioned above, I am not sure it can have a kick-back activity against Phomopsis, but at least it will provide a good kick-back activity against downy mildew. It looks like the next opening will be on or after Tuesday.

FYI: For our plots, we sprayed mancozeb earlier this week before the rain for older Chardonnay plot where we started to see Phomopsis in the last two years, but did not spray "organic" plot where we have not seen Phomopsis. The timing for next application will be either late next week or early in the week after, depending on the weather conditions.