UGA Extension Viticulture Blog

Gramoxone (Paraquat) Injury to Young Vines

The school of hard knocks is tough, but lessons learned can be important and they tend to stick.  I encountered an issue in one of our just-planted, on-farm research blocks yesterday.  Vines were collapsing and dying, and symptomatic vines presented a combination of red leaves, and/or leaves with red to…
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Downy Mildew Field Failures in 2018

This article (see link) reviews the state of grape downy mildew resistance in Georgia as of the close of the 2018 season.  Field failures when using strobilurin (QoI) fungicides have been confirmed in Georgia for both research and multiple commercial vineyard sites.  Of major import, efficacy of several downy mildew…
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Pierce’s Disease Update

Pierce’s disease (PD), caused by the bacterium Xylella fastidiosa, is quite prevalent in many locations this year.  The cold winter this last year has not made up for the two previous warm winters, so the bacterium has survived and prospered over the last 2-3 years. Unfortunately, once vines are infected…
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Botrytis Resistance Testing

Some of you already tried sending Botrytis samples to Clemson for fungicide resistance testing — only to find out that the service was no longer offered. However, Dr. Guido Schnabel will be conducting studies with the PROFILE system in early September, so he is volunteering to take Botrytis samples at…
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Crown Gall on Muscadine Grapes in North Georgia

I was at a muscadine meeting in Americus, GA earlier this week (Thursday), and I made comment on how I have never really observed significant crown gall on muscadine grapes in Georgia. I scheduled a muscadine grape visit with a producer near Ellijay, GA the next day, and I can…
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Black Rot Issues

We have been receiving multiple grape samples with black rot in our diagnostic clinic.  Only one or two infected grapes can provide a vast number of spores for secondary infections of clusters going forward.  Prevalent rainfall has made control difficult. The disease cycle will slow as grapes mature, but fruit…
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Downy Mildew, Powdery Mildew, and Black Rot Warnings

We are starting to see diseases pop up on both European vinifera and hybrid grapes.  For some of these, such as anthracnose and Phomopsis, much of the initial infection occurred much earlier.  The goal now would be to prevent secondary spread — especially to developing clusters.  Relative downy mildew, Sarah…
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Downy Mildew Resistance in Georgia

Sarah Campbell, a graduate student in the Plant Pathology Department at the University of Georgia, has been reviewing our situation with downy mildew resistance to three fungicide classes utilized in Georgia.  The maps in the document below show the counties which she has surveyed and whether resistance has been found…
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