UGA Extension Viticulture Blog

Bloom

Bloom is upon us in bunch grape vineyards in the piedmont and mountains of north Georgia. This is likely also the case in most bunch grape vineyards in Alabama, Tennessee, South Carolina, and North Carolina, excepting those vineyards planted above 2,000 ft. above sea level and/or those with late-blooming cultivars.

Bloom in a Chambourcin vineyard in Cleveland, GA.

And, thankfully, this year looks to be a drier, warmer bloom-fruit set period relative to last year (which was really as bad as it gets). Warm, dry weather during bloom hastens and improves fruit set relative to cool, wet weather. Good news there. Let’s hope the weather forecast is accurate.

Since bloom also marks the beginning of the critical period for fungal disease management of clusters, dry weather is good news yet again. But – please remain diligent in protecting clusters from diseases from bloom through bunch closure. Here are some links to help y’all with your disease management from the bloom through bunch closure period

http://extension.uga.edu/publications/detail.html?number=C1151

http://www.smallfruits.org/assets/documents/ipm-guides/BunchGrapeSprayGuide.pdf

 

Things to do in the vineyard during bloom:

Sample tissues (petiole and/or leaf blades) for nutrient analyses. These can be submitted to UGA’s Soil, Plant, and Water Laboratory (2400 College Station Road, Athens, Georgia 30602-9105). Please contact your local extension office for assistance with tissue sampling and submission for analyses. Here are some helpful links regarding grapevine tissue sampling for nutrient analysis (FYI – we soon plan on releasing a new extension bulletin on grapevine tissue sampling; stay tuned!):

https://articles.extension.org/pages/31517/monitoring-grapevine-nutrition

www.uvm.edu/~fruit/grapes/gr_horticulture/GrapevineNutrition.pdf

Apply fertilizer (if needed). Research has shown that bloom is a good time to apply fertilizer to the soil as roots are highly active in their growth at this time and are thus able to uptake soil mineral nutrients. Don’t simply assume your vineyard needs fertilizer; use your records and observations to guide actions. Use previous soil and plant tissue reports to help diagnose nutrient needs. Check records to see the last time fertilizer was applied. Recall visual observations of foliar nutrient deficiency symptoms from late last summer. Are certain blocks of vines showing attenuated growth patterns? and is this reduced growth consistent with land topographical patterns that point to rocky, low organic matter soil? Has crop yield steadily declined over time (sub optimal nutrient status can limit fruit set, berry number per cluster, cluster weight, and thus crop yield). Use these suggestions and more to help guide your fertilization practices.

Shoot positioning. The optimal time for grapevine shoot thinning has passed; vegetative shoots are now becoming lignified at their junction with the spur/cane and have begun to fasten to neighboring shoots and trellis wires with tendrils. Shoot positioning is an important canopy management practice that trains shoots to the intended training/trellising system. The benefits of the chosen trellising system are limited by poor, or lack of, shoot positioning. Good shoot positioning aids in fruit zone airflow which reduces drying time and improves spray penetration, ultimately aiding in fungal disease management of clusters. Shoot positioning also limits foliar overlapping, optimizes radiation capture, and improves overall net photosynthesis and carbon gain; the result is a healthier vine and canopy that will aid in fruit maturation in the post-veraison period. Here is a link to shoot positioning:

https://articles.extension.org/pages/33061/canopy-management:-shoot-positioning

A lyre system after shoot positioning. Note the open center between canopies which greatly aids in radiation interception, air movement, tissue drying, and spray penetration through the canopy.