Leaf Thinning for vineyarads and wineries

Leaf Thinning

Leaf thinning is a key step towards quality fruit at harvest. The June 2017 program discussed the practice of leaf thinning around the world, the benefits to growers and winemakers, as well as location, timing, and quantitative results.

Grower Benefits

  • Better air flow
  • Better spray penetration
  • Less disease pressure
  • Even ripening
  • Easier harvest

Winemaker Benefits

  • Consistent fruit quality
  • Less disease
  • Color stability
  • Enhanced phenolics
  • More fruit, less vegetative flavors

pdfDownload the presentation (minus videos) here

Video 1: Vit Minute Leaf Pulling
Video 2: Jordan Winery: Leaf pulling preparing our grapevines for ripening
Video 3: One Acre in Napa Valley – Episode # 5 Leaf removal
Bonus Video:  Sheep thinning leaves at Shannon Ridge

Other Primary Resources: Recent Advances in Grapevine Canopy Management – July 16, 2009 University of California, Davis

dormant vines

Spring Vineyard Checklist

  • Order replacement vines. If you are wanting to use cuttings from your own vines or from another grower, get permission and coordinate with them about their pruning schedule.
  • Be sure that you have the chemicals and supplies that you will need for the first month or so of spraying and vineyard maintenance
  • Check your spray equipment for damage due to freezing this winter or need for maintenance from last season.
  • Decide on the winter pruning method you are going to use this spring. Remember that pruning can stimulate bud break. So consider one of the multiple stage pruning methods that have been talked about over recent years.
  • Re acquaint yourself with the life cycles of the pests that have plagued you in the past and layout a theoretical spray program for their control. “The plan is worthless but the process of deriving the plan is priceless!” Ike Eisenhower talking about the Normandy Invasion planning.
  • If you have not had a soil test in the last 3 to 5 years, it is time to take another one. You know your soil better than anyone. If you have distinct differences, take separate samples from each area…very sandy and more clayey.
  • grape bud slicesWhen you are ready to begin your final pruning stage this spring, it would be good to examine your buds for damage first. You will want to look at several samples across the vineyard. I usually do this in the field with a multi-lens magnifying glass and a razor blade knife. Look at the buds that are closer to the end of the shoot, since you will be cutting this part of the shoot off in your final pruning. If you find considerable damage, it would be advisable to plan to leave more buds than you normally would.
  • All of those suckers are not your enemy. We use interstate 40 as a rule of thumb for varietal selection. Most think that you can be pretty safe over the long haul to plant Vitis vinifera vines south of I-40. However, the farther north of I-40 your vineyard is located, the more you should consider French-American hybrids. That does not mean that the Vitis vinifera vineyards south of I-40 are always safe. Freeze damage is cumulative. So we get a little each year. And that damage can be the entry point for insects and fungus. So it is beneficial to have a multi trunk vineyard with planned renewal. Plan to have two trunks. Each year as you prune through the vineyard, inspect the trunks for damage. As damage increases, use those suckers as renewal trunks. It is possible to not miss a crop by using those suckers as renewals.
  • Spray Schedule 1st spray when shoots are 3”; 2nd spray when shoots are 10”; 3rd spray pre bloom; 4th spray is post bloom; 5th through the 9th are cover sprays and every 14 days unless rain is frequent and then reduce the interval to 7 or 10 days. You need to be ready but remain flexible. You cannot cure black rot in a berry. All you can do is prevent it. So as rain becomes less frequent, watch the weather and be prepared to spray your grapes before the rain arrives. One of the most important spray applications is the “pre-closure spray”. This is particularly important for varietals that form tight clusters. The idea is to get that last spray into the center of the cluster before it closes up. If black rot is established inside the cluster and it is closed to your spray program, it will spread unabated no matter how many times you spray.The 1st and 2nd applications can come pretty close together depending on the moisture and temperature.

GLYPHOSATE that wonder chemical that keeps you from being the “best hoe-r on the block”

MANCOZEB has a 66-day harvest interval so it can only be used for the early sprays.

RALLY is the workhorse for black rot prevention

ABOUND is the rotational spray for black rot prevention to prevent developing immunity in the existing strain of fungus.

SEVIN is the workhorse insecticide for chewing insects.

PROVADO is good with sucking insects.

MICRO NUTRIENT FERTILIZER an insurance policy for nutrient imbalances can be applied in a tank mix with other sprays.

SURFLAN is a pre-emergent chemical that can be tank mixed with glyphosate and sprayed in the row and other areas where weeds are a problem.


Pre-bloom is after the flowers are evident but before they have opened.

Post-bloom is well you know…

All of the above applications can use Mancozeb, so you need to plan on at least 4 applications. If insects become evident, it is best to spray before or after bloom to avoid harming the beneficial insects in the vineyard.

ABOUND is a good chemical to alternate with RALLY. RALLY is less expensive so will probably be the chemical of choice. But to prevent a strain of Rally resistant fungi from developing in your vineyard it is good to intersperse a couple rounds of ABOUND to be safe.

Contributed by Tom Knots, January 2016 meeting.

Dr William McGlynn at sharing results of the 2014 wine quality project

Wine Quality Project with Dr McGlynn

The April meeting program featured OSU’s Dr. William McGlynn, sharing results of the 2014 Oklahoma Wine Quality Project.   Dr. McGlynn’s presentation sparked a great deal of discussion on improving quality in the vineyard and winery processes.