UGA Extension Viticulture Blog

Baby! / shoot thinning / disease management

Grapes are important.

But then I hear news like I did today and I think… grapes are still important.

BUT… not as important as this amazing news:

Kenneth Clay Eason was born as healthy as they come – 9 lbs 14 oz of pure miracle and beauty!

“Clay” is the son of two proud parents: Nathan Eason, White County Extension Agent and Extension Coordinator and UGA Extension Viticulture Team member, and his wife, Kristen.

Congratulations Nathan and Kristen! And welcome to the world, Clay.  The world is a better place with you in it.

Canopy management: Shoot thinning is the first seasonal canopy management task.  The typical recommendation is to aim for roughly 3 to 6 shoots per linear foot of fruit zone (see picture below).  This means that 6 to 12 shoots per linear foot of row in systems with two fruit zones, such as the Geneva Double Curtain or Lyre system.  Lower shoot densities are recommended in cultivars susceptible to bunch rot or over-cropping, in low vigor vines, and in systems with confined fruit zones (like VSP). Higher shoot densities can be retained in cultivars less susceptible to bunch rot or over-cropping, in high vigor vines, and in systems with divided fruit zones (like Watson).  Don’t count the shoots on every vine – you will never finish.  Count bud densities as you shoot thin four or five vines; take a step back, get a mental image of what your target shoot density looks like, and get to work.  You would be surprised how little you might stray from the target with this method.

Like all canopy management practices, time is of essence when implementing shoot thinning.  This practice is optimally executed when shoots are roughly six to eight inches long.  This is when developing clusters can be visualized, when shoots are easily rubbed off the cordon with your thumb, and before the point when tendrils starts grabbing neighbor shoots.  This practice is much less efficient when shoots are becoming longer than 18-24 inches, becoming lignified at their junction with spurs and cordons, and are tied up by tendrils. If pruning was completed, then shoot thinning will be easier; if  several three and four bud spurs exist, it can quickly become a jungle.  Finish this practice ASAP. Next up in canopy management are shoot positioning and fruit zone leaf removal.

Four shoots per linear foot of row in a bilateral cordon system trained to vertical shoot positioning (VSP). Shoot thinning was completed about 10 days before this photo was taken.

Disease management: Dr. Phil Brannen is our UGA Extension Viticulture Team Grape Pathology Specialist.  He can be reached at pbrannen@uga.edu.

In bunch winegrape vineyards, phomopsis, powdery mildew, downy mildew, and black rot all need managed from now through pre-bloom (roughly 28 to 36″ shoots).

Good disease management resources are Dr. Mizuho Nita’s blog (grapepathology.blogspot.com), the Southeast Regional Bunch Grape Integrated Management Guide (www.smallfruits.org/assets/documents/ipm-guides/BunchGrapeSprayGuide.pdf), the Southeast Regional Muscadine Grape Integrated Management Guide (www.smallfruits.org/assets/documents/ipm-guides/Muscadine-IMG.pdf), and the UGA Extension Viticulture Blog – particularly when Phil posts updates.