Black rot long term impact

spaniel · Apr 24, 2016

We had an incredibly wet July last year. Water flowing in a river through my Marquette, I had never seen standing water in that location in the decade we have owned the land. Much less enough to make a river.

The end result was that I had black rot set in to the Marquette terribly, and other varieties in a less wet location to a lesser extent. I did spray, but given my job it was not a diligent schedule one would need to address the issue.

My vines are waking up. Last fall I marked the vines clearly dead and ordered replacements. Well, come spring, I have three times as many vines which appear completely dead at this point. Our winter was VERY mild, except for an unusually cold late March/April, so I can only blame the black rot. Is it typical for it to take out vines? Previously I had considered it a threat to the crop but not the vine long-term. The Marquette, the hardest hit, I considered last year's crop a complete loss to black rot and threw it away.

grapeman · Apr 25, 2016

The black rot problem certainly can weaken the vines and make them look kind of bad. They may be alive at this point and just not waking up yet. Be sure to begin the spray program early and keep up with the schedule. As the vines begin to grow you will be able to verify if those vines are actually dead. Marquette vines can look bad but will grow alright. Sometimes though if they are very weak, they will just lag behind. They also just plain don't like wet feet so if that area kept wet for a long time it may have killed the vine. Good luck with them.

dwhill40 · Apr 26, 2016

Start a spray program. Consider black rot spores to be a zombie horde. I went three years with minimal spraying and it continued to lurk. A good warm wet season with a decent infection and it will be everywhere. Spray a dormant spray of copper or sulfer-lime pre-budbreak. Spray post bud break, etc etc. Your region will probably have a university with a good spray program template. Learn about myclbutanil, mancozeb, strobilurins. If you don't want to spray strong fungicides... grow muscadines. Good Luck!!!

spaniel · Apr 28, 2016

Thanks both of you. Yes I have the proper sprays, but with 30%+ travel the schedule can be difficult to maintain. Last year with the rain we got…I cannot be over-dramatic about it…no amount of spraying would have done any good.

I'm hoping the wet feet thing was a one time issue. In a decade owning the property, this was the only time it was bad enough to really be a problem. If I were to re-plant the 30-vine row would be two 15s on the north half of the plot, but it's too late for that now.

We'll see how it goes with the "dead" ones, I'll let them sit and see if they come back. I already have my replacements for this year in the ground so there is nothing to be gained by digging them out right now.

barbiek · Jun 23, 2016

My 2 month old Marquette seems to have black rot? I didn't spray them cuz I thought they didn't need sprayed the first year? And it's the only vine it's on in the vineyard but I do have a few leafs a few vines down that look like they had been spray painted with a bronzer any comment appreciated
Thanks

barbiek · Jun 23, 2016

Here is a pic of the bronze leaf
This pic is upside down

grapeman · Jun 23, 2016

All vines no matter their age need to be controlled for diseases. The younger ones generally have less dense foliage so don't stay wet as long but as you see in the picture they can get wet by any means, and that can be enough for an infection to occur. That leaf could be the result of some insects feeding on the bottom of it causing the discoloration.

barbiek · Jun 23, 2016

Thank you grapeman! Never had that accur so early in the game. And it has been wet around here. Should I use Mancozeb ? And I was thinking insects too on the bronze colored leaf was gonna get out magnafieng glass. Should I just pick the leaf with the black rot off and spray?

saddlebronze · Jun 23, 2016

Mancozeb is a good product, but you have a limit on the number of applications per year and pre-harvest limits. Also, you need to rotate fungicides throughout the year or you will develop resistant strains. I like to use Mancozeb until just after bloom and then switch to captan or stylet oil for later applications. I also use a bourdeaux spray at bud break. Dramatic difference in black rot with a regular spray program on Marquette. If you are travelling, do a spray every time you are home or each week when you get a dry day. We are having a very dry summer so far so the disease pressure is low, but the problem with black rot is once you see it, the crop is lost, so you have to stay on it.