What causes grapes to shrivel up before harvest?
I have a grapevine in my garden that looks healthy enough and each year it seems to be doing fine, only for the grapes to shrivel up before they are ready to harvest. I have some pics somewhere from last ear but m having trouble finding them. This is an old vine, several years at least and planted by the previous owner of our property. Should I just dig it out and plant new vines?
Posted
by: Fred Johnson
(3 points)
Posted: March 24, 2013
Answers
Typically, black rot is the disease that causes berries to shrivel. (Crown gall is usually associated with graft-unions and trunks and causes vine death.) Removing the mummies from the canopy can help lower the inoculum for the next year, as does vigorous pruning in the winter. More importantly, you'll need to control the disease in the early part of the season with fungicides or canopy management practices.
If you see small, reddish splotches on the leaves (with small black dots in the splotches), that's the start of black rot. The fruit will soon be infected. Once the fruit reaches about 5-10 Brix, it's not susceptible anymore. Most black rot infections occur early in the season (May-June).
If you continue to have problems with black rot and can't control the disease through opening up the canopy or fungicides, you'll have to realize that the site is wrong for that variety or perhaps any variety.
If you see small, reddish splotches on the leaves (with small black dots in the splotches), that's the start of black rot. The fruit will soon be infected. Once the fruit reaches about 5-10 Brix, it's not susceptible anymore. Most black rot infections occur early in the season (May-June).
If you continue to have problems with black rot and can't control the disease through opening up the canopy or fungicides, you'll have to realize that the site is wrong for that variety or perhaps any variety.
Posted
by: Carl Helrich
(12 points)
Posted: April 13, 2013
David Hughes commented,
nice answer Carl. I added some pictures that might help. Do please add you own if you have some. thanks over 11 years ago.
nice answer Carl. I added some pictures that might help. Do please add you own if you have some. thanks over 11 years ago.
I wanted to add some images of blackrot to compliment some of the answers.
Black rot
Guignardia bidwellii (Ellis) Viala & Ravaz
Symptoms on a grapevine leaf: necrotic circular lesions scattered over lamina.
Black rot on grapes
Posted
by: David Hughes
(68 points)
Posted: April 13, 2013
There are a few fungal pathogens that may cause the fruits to shrivel Fred. Crown gall is one. I think that there would be other symptoms on the plant though. Black rot can cause mummified grapes too. You may need to think about applying a fungicide to keep the disease in check rather than tear out the vine.
Posted
by: Maggie Muffins
(1 point)
Posted: March 27, 2013
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