UGA Extension Viticulture Blog

Hey rain… leave!

“Rain, rain go away” sounds too fluffy and soft to me at this point… emotions are involved now. 

RAIN AND FARMING GRAPES: Growers become rather animated when talking about the weather and how it is (currently negatively) affecting their crop. I completely share their sentiment. It is interesting to see how much more one cares about the weather when they have their crop’s success at stake relative to pre-farming days. I know that I personally cared a lot less about the weather before I started in the vineyard industry. But since 2006 or so, the weather between May and September has sometimes dictated stress  levels; I am sure many reading this post have had similar experiences. What this means in light of this year is that I have been grumpy at times (although I do my best to hide it when I am). It’s not logical; we have no control of mother nature. And we do grow grapes in a humid, subtropical climate. Can you believe plant pathologists actually like these weather patterns?!

I would urge all to pray, dance, sing, or whatever it is you feel will aid in parting the clouds for some consistent blue skies.

 

UPDATE: We have been seeing frequent bouts of rain from bloom through veraison (start of grape ripening), the latter which is well underway here in Georgia and North Carolina, and also in most regions in Virginia.  Many of the early fresh market muscadines (e.g. Early Fry) are being harvested in south Georgia while Carlos and Noble (the “wine” muscadines) are just starting veraison. Some winegrowers in south Georgia and the Georgia piedmont have already harvested their Blanc du Bois and will be harvesting their Lomanto very soon if they have not already. Many North Georgia vineyards will soon begin to harvest early whites and fruit used for sparkling production. Reds will follow in late August and September; harvest date will depend on cultivar, wine style production goals, and vineyard site.

Veraison in Merlot

Veraison in Chambourcin

Veraison in Ison

POST-VERAISON COMMENTS: In the meantime, here are some “grape chores” (Small fruits – grape chores July 2018) that will soon be published in the Small Fruit News which can be found here www.smallfruits.org/  Some of these chores will be more or less meaningful to your personal situation as related to the current ripening stage at your vineyard.

In light of the above comments on the rain… please be proactive about managing fungal diseases – particularly late season rots (ripe, bitter, sour, and Botrytis bunch rot) and downy mildew. Follow pest management guidelines which can be found here (https://docs.google.com/spreadsheets/d/1NaIKdGpiLcRMrAOtQpqQca2WYNqcPxJSxkudY9ViwZA/edit#gid=0), here (www.smallfruits.org/assets/documents/ipm-guides/BunchGrapeSprayGuide.pdf), and here (www.smallfruits.org/assets/documents/ipm-guides/Muscadine-IMG.pdf). Please pay attention to label regulations, especially pre-harvest intervals.

Since we have been receiving frequent bouts of rain since bloom, there is high potential for latent infections from Botrytis/other rots to manifest – things may look okay now, but that can change quickly as grapes soften, accumulate sugar, and decline in acidity.  Please do all you can to keep canopies and fruit-zones open so drying time is reduced and spray penetration is optimized. Please also be realistic about harvest decisions and goals.  Use a mix of chemical (Brix, pH, TA) and sensory (varietal character in whites, skin phenolic ripeness in reds, seed color, rot severity) observations to evaluate when to harvest. Keep in mind that 5% rot can turn into 20% rot seemingly overnight in these types of conditions… even at relatively low Brix levels. However, also keep in mind that several whites can have very nice varietal character even at relatively low Brix levels. Make decisions based on chemistry/varietal character and cluster integrity to optimize both crop quantity (e.g. prevent excessive crop loss due to rot) and wine quality potential.

A recently-taken picture of a well-maintained canopy in which spray penetration will be optimized and drying time and reduced throughout post-veraison.

A recently-taken picture of a well-maintained fruit zone in which clusters will dry relatively fast and receive good fungicide coverage.

Blanc du Bois is highly susceptible to rots. But can also have nice varietal character before rots set in.

Botrytis on Cabernet franc harvested from a shaded fruit zone.

Chardonnay that was harvested a bit late in a wet season.

 

We’re good on water – here’s to hoping for drier weather from now until October.

BEST OF LUCK TO ALL.

Please give a holler if you need anything.

Cain