This spring I planted some muscadines, a Black Spanish (aka Lenoir/Jacquez) and a Lomanto vine. All are doing remarkably well except the Black Spanish vine. It grew at an alarming rate, from a 1/8th inch diameter twig with roots, to two trunks 5' up to the wire and four foot down in each direction, lots of canes, the cordons are as thick as my thumb at the head, but now it has this leaf disease. Other grapes seem to be unaffected. If it is downy mildew, unsure of the cause, it has been very dry recently, although humidity has been high. Would you treat this late in the year? I rooted two cuttings from the same plant earlier this year and both have similar leaf lesions. I was looking for low maintenance vines, this may have to go.
is this downy mildew?
- Thread starter Huba Huba
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Cynewulf
Senior Member
It looks like downy mildew to me since you have the oil spots on the top and fuzzy brown on the bottom of the leaves. It’s too late to spray with a preventative material like Captan or mancozeb, but you can try phosphorus acid which has some kick back properties. You want clean foliage both to keep the disease from gaining a foothold in your vineyard and to help store up energy for next year as the vines enter dormancy. That said, don’t despair as I deal with it almost every year at the end of the season when the rains start picking up.
"try phosphorus acid which has some kick back properties".
Could you define "kick back " properties? Would this type of product be carried by big box stores or only ag supply type. No grapes around here, unless it's used in corn/rice /soybeans I will probably have to order online
Could you define "kick back " properties? Would this type of product be carried by big box stores or only ag supply type. No grapes around here, unless it's used in corn/rice /soybeans I will probably have to order online
Cynewulf
Senior Member
It just means it can be curative. Most fungicides we use in the vineyard are preventative and have to be sprayed before an infection in order to be effective, but there are some that have some efficacy post infection. Even then, the timeframe after an infection is limited to a day or two. You might be able to find it at an ag/farm supply, though I ordered mine from Amazon. I bought Garden Phos, which seems to have gone up 30% since last year. Reliant is another brand.
thank you. I see it on amazon
