Powdery Mildew

Asked August 3, 2018, 2:37 PM EDT

I have a 2 acre vineyard on Setterbo Rd. I have poweredy mildew. The first signs showed up arounf the 4th of July. I sprayed Stylete Oil (1%) on the 10th and again on the 23rd. (2%). We plan another treatment using coper sulphate and sulfer this weekend and the stylete (2%) on 10 days. Do you have any suggestions on a better treatment strategy? I fear I have lost most my crop this year but I am not sure. i am a weekend farmer but I do have someone working on my vineyard the resides in the area (Warren Schaub). Hope you can help.

Wayne County Michigan

1 Response

If you are growing grapes that are susceptible to powdery mildew you should start your disease control sprays before the disease shows up since you will not be able to stop or cure it after it gets started. Are you organic and that is why you are only using oil, sulfur and copper for disease control?
The sulfur is probably a little better than the JMS Stylet oil for powdery mildew but both are only fair to good. The copper has no effect on powdery mildew so I guess you are spraying it for downy mildew.
All you can do is keep up your program at this point. You will need excellent spray coverage as these materials are only protectants so you need to cover every surface.
Next season start with a dormant spray to reduce the amount of overwintering powdery mildew. http://msue.anr.msu.edu/news/its_not_too_late_for_dormant_sprays_in_grapes
That should give you good control during early shoot growth. Immediately after bloom you should begin you powdery mildew control sprays, especially since you have it on the fruit this year.
There are no fungicides I know of that will knock out powdery mildew once it is established on the vine. Now all you can do is slow down the spread.
If you have any other questions feel free to contact me directly.