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.

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This Post Has 5 Comments

  1. I have been battling Phomopsis over the last couple of years in my vines the last couple of years. This year I have been a lot more diligent with my spray program. I was reviewing the 2016 PMG for Home Fruit, including grape and noticed that the spray guide for Mancozeb (page 17) recommends 3.0-4.0 tbsp Mancozeb F1 per gallon. I have Bonide Flowable Mancozeb and the label recommends 3-4 tsp per gallon. Why the difference?

  2. Hi, It could be either 1) simple typo or 2) difference in formulation. Some formulation is more concentrated than others. However, since teaspoon is about 5 ml and table spoon is about 15 ml, I have a feeling it was typo. Please follow the label. Our guides are more for your reference, and we cannot cover all the materials available in the market.

    In anyways, please keep your vines protected. If you are located in VA or surrounding area, we are having a long period of rain. If you can, get a hold of a phosphonate (there is a product called Agri-Fos), which is a systemic material and works well against downy mildew. You can mix mancozeb and Agri-fos together to spray.

  3. This has been an ongoing problem for winery owners. I think your solution is a good one, however I think we still need to pay attention to issues like these!

  4. Hi Robbie,
    We have only sprayed fixed copper so far. Since they are on the top of the hill (good air circulation) and not much of history of Phomopsis, so far, they look pretty clean. We will see how it will progress when temperature gets higher, though.

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