I just picked up a baby grape vine today. I’m not familiar with grapes but noticing this on two leaves I looked it up and seem to be downy mildew? Is it? If so, should I bother to treat it or exchange it? how contagious is this stuff? I’m concerned that the other ones would be suspect.
Black rot maybe? I have some of that on my grapevines around my chicken run. I let the wild strawberry growing around the base get a little too tall and the air circulation got reduced and the moisture built up.
Since you are in Alaska you should verify that this variety will fruit in your climate. Then search for the variety and how other growers are treating it in is growing cycle within Alaska. Almost all grapes need to be sprayed weekly.
Yes that is black rot… bad stuff! If it is only on a couple leaves I would pick them off and maybe you can dodge it for now. I need to do a couple sprays of myclobutanil to keep black rot at bay on my grapes. In fact I need to do the second spray about now…
I have a seedless concord grape vine that has never been sprayed with anything… and I get good grapes almost every year (2019 late late frost exception)…
I prune it, it has a trellis, and I do have to bag the fruit (or birds will get the large majority).
One thing I do that I think helps is this… each year about this time (did this this morning)… when my grape clusters start getting some size to them (space between fruit is getting tight)… I prune my grape vine canopy… for morning sun exposure.
On the Eastern side (where the morning sun comes up) simply remove any foliage that would block that morning sun. Mine often has lots of leaves down low around the grape clusters… that at that point are really not getting much sun at all … the canopy overhead is thick and getting all the sun. I remove all leaves that are near the fruit (open up for air flow) and any canopy that is blocking morning sun… (let the cooler morning sun get to them and dry them out early in the day).
But leave any canopy that shades from mid day and evening sun.
Open up for air flow, and morning sun exposure… and it will help.
Below shows what I took off and used it for mulch.
King of the north is one of the very few varieties that is both hardy and fruits early enough. So is valiant. I picked a frotenac, which is hardy but does not have enough time to fruit, like ever… I’m keeping the frontenac potted and bringing it into the house in late April to get it to wake up early. Even the valiant grape did not wake up until June first, it takes they long for the soil to warm enough to wake them.
The valiant is on its third year and I haven’t seen this on it before.