Downy Mildew

[Handy Andy]

I know nothing, this is my first time growing vines to make wine. I should have sprayed earlier.

I have just sprayed for the first time against Downy Mildew. I noted a small problem on some of my vine leaves in one vineyard some weeks ago, and never thought anything of it. I went down to the vineyards last week and noted it had spread and now lots of the grapes were covered in a grey material. I went to the local agricultural advisory service and they told me had downy mildew and needed to treat it immediately to stop it spreading.

My Question is are those grapes with the downy mildew covering now ruined or might they recover????

 

[user 36973]

You may want to post vineyard questions in the grape growing forum on this site for better visibility to your questions.

Pictures are worth a thousand words, so please attach a photo of your disease and the grape varietal for better identification. From what you've described, the "grey material" may be powdery mildew. Downy mildew has yellow/brown spots on the top of the leaves with a grey discoloration on the back of the leaves opposite from the yellow spots. There are many pesticides that treat powdery mildew, including JMS stylet oil, an organic option, if that is your direction.

Here is a comprehensive guide on what pesticides work for the various diseases:
https://ag.purdue.edu/hla/Hort/Documents/ID-465.pdf
I've attached an overview sheet on disease control to help guide you.

 

[Handy Andy]

Thanks, can the infected grapes recover and be use-able.

 

[user 36973]

Caveat that powdery mildew doesn't typically haunt my vineyard, so I don't have loads of experience with fighting it. I'd say that it depends on how far along the infection is as to whether the grapes are salvageable. The problem is that the mold is rapidly making more spores to infect the rest of your grapes. So, It is best to remove the affected clusters and treat the vines. The infection can also damage the shoots and impact the fruitfulness next year.

 

[Handy Andy]

I note some vines were doing badly in comparison with the others, before the mildew problem became apparent. I wonder if this is because they had mildew last year!

 

[Dennis Griffith]

To answer your question, no. I typically pull grapes (or bunches) that are damaged in some way. But once they get this fungus, it was damaged them and they will not recover. I started a soil drench program this year to fight such fungi using a product called Actinovate. And for some of the new vines that I planted this year, a did a root soak prior to planting to help inoculate the vines. Looks like it is working so far.