The last post I wrote on May 17 was optimistic for a good fruit set given the wonderful weather we were experiencing last week. Key word here is “were”.
The weather has been rather wet, cool, and rainy from this past weekend, and continuing through tomorrow. This has been particularly true throughout northern GA, but I’ve also received reports of very rainy weather in NC. Not exactly sure, but at a glance, VA seemed to be north of the most recent foul weather patterns.
What does this mean?
Fruit set: Some in the GA foothills my already be well into fruit set in early varieties, like Chardonnay, and still in the late-bloom period in later varieties. However, many in Rabun, Towns, Gilmer, and surrounding counties with higher elevations are likely right smack in the middle of bloom in some varieties. Regardless of where your vineyard is located, the current rainy weather we are experiencing could adversely affect germination and pollen tube growth rates, thus reducing fruit set percent – especially for those still in some phase of the bloom period. Take home: if you are at pre-bloom or post-fruit set, fruit set will likely be less affected by the rainy weather than if your are actually in bloom.
To follow up on Clark MacAllister’s (clarkmac on the post) recent post:
Disease management: This is a common theme, and will continue to be this time of year, but I would urge you to read Dr. Mizuho Nita’s blog (https://grapepathology.blogspot.com/). Here, his recent two posts explain the importance of managing downy, powdery, and black rot (as well as phomopsis) over the next several weeks. This is especially true given our recent weather patterns – downy mildew thrives in wet weather – see Clark’s post, but I also received word that downy mildew has been observed on grapevines in Blairsville. Remember – bloom and post-fruit set are critical periods when flowers / fruit can become infected, and these are manifested later in the season as “latent infections” around veraison and as berries ripen. Take home: given the weather patterns we are experiencing during these critical grapevine growth stages, please consider disease management to be of paramount importance in order to protect your crop from both primary and latent infections. It looks like Thursday and Friday will be good opportunities to get out and spray fungicides in northern Georgia, as rain is not forecasted again until Sunday.
Best of luck to everyone.
Further reading:
https://www.isaacslab.ent.msu.edu/grapescout/meetings/diseasesduringbloom.pdf
https://msue.anr.msu.edu/news/the_challenges_of_disease_control_during_rainy_spells
