The Q&A Archives: Preventatives To Minimize Next Year's Black Rot Damage On Grapevine

Question: Bought a new house last year and was pleased to find an old grapevine already trellised over an arbor. Unfortunately, as we discovered just before the grapes ripened, it was also infected with black rot. This year I didn't get to clearing out the area in time - but have now cleaned out all the stacked firewood underneath, raked out the ground, put down cedar mulch, pulled down the rotting latticework underpinning, trimmed all the overhanging tree branches (weeping and wild black cherry) to let in the light and am judiciously plucking out rotted fruit as it appears and have clipped as many infected leaves as I've dared (it's pretty sparse - I get kind of wild with clippers - but it is putting out new growth) and making sure I keep anything picked up off the ground. (Grapes are scuppernongs)

I have two areas of concern:

1. This winter I had thought to prop up the vines off the frame and perhaps wash down the wood with a mild bleach solution and then paint it - of course I'm assuming the spores also overwintered in the damp wood - what thoughts do you have on this, or what tips.

2. I understand there is an organic fungicide (some sort of sulfate/sulfide) that is recommended, but I believe I've missed the proper times for dusting already (before flowering and before setting fruit I think). We have a dog and I've never particularly like using any type of pesticide/fungicide unless absolutely necessary - so I guess my question is; with the maintenance and pruning I'm performing this season, as well as the painting I'd thought to do on the arbor over the fall - do you think that would be enough to minimize the damage next season? This season I don't think there is a leaf that's not infected - and while a few grapes may make it to maturity, it'll be just a few.

While I am planning on adding one or two more resistant varieties (the vine does not originate on my

Answer: As you have already realized, sanitation is very important in reducing reinfection. Additional steps would include proper pruning and possibly preventive spraying. Pruning should be done in late winter and involves cutting the vine back very hard, in most cases to just a few buds. (The trimmings are then removed and destroyed.) This would allow you room to work on the arbor as well.

A spray routine would depend on the incidence of specific problems in your area as well as the built-in tolerances and susceptibilities of your vines. Your county extension (255-5522) should be able to help you determine the most effective program in your area for the particular varieties you have. In addition, grapes do best in an area with full sun and good air circulation so anything you can do to improve those conditions is worthwhile.

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