Grape Breeding and Enology

Annie Klodd, University of Minnesota Extension, [email protected]

Many vineyards across Minnesota have been severely affected by winter injury, while others survived the winter well. For the vineyards reporting winter damage, many are reporting partial or entire blocks of one variety to have died to the ground, often leaving behind multiple suckers per vine. So far, more damage has been reported on lower sites with higher water tables or more wet, humid environments; while sites on higher ground seem to have faired better overall. Damage also varies by variety. It is also likely that vines that were less healthy going into last winter suffered more extensive damage, although more data must be collected in order to make that conclusion. A formal multi-state survey will be conducted to determine which varieties, site types, and geographic areas were most affected.

Rejuvenating Grapevines Following Severe Winter Damage

If a vine is dead to the ground but has several healthy suckers growing from the base of the trunk, leave roughly five suckers on the vine and select one to train up to become a replacement trunk. If the vine has more than about five suckers, trim the rest off; or if you have less than five, leave as many as you can. Choose a healthy, strong sucker to be your new trunk, but avoid selecting a bull cane (a bull cane is more than pinky-finger diameter, with wide bud spacing). The reason to leave extra suckers is to distribute some of the excess energy that is in the vine's root system and reduce the risk of the vine developing bull canes. Once you have chosen your new "trunk" shoot, use tapener tape or other fasteners to secure it vertically upward onto a fresh bamboo pole or rebar.

In order to spray herbicides, treat these as you would new vines; apply grow tubes so that you can safely spray herbicide around the vines without injuring the suckers. Try to maneuver the suckers into the grow tube. If the suckers are running along the ground and are very thick, it may be too late to get them all into the grow tube without breaking some. At that point, you may consider leaving the weeds, weed-whacking around the vines instead of spraying, or removing the shoots that are causing problems. Leaving the weeds may take away excess vigor from the vines, if that is an issue on the particular site. Therefore, these decisions depend on the needs and goals of the particular vineyard to some extent.

Remove the grow tubes no later than October, or whenever you are done with your last herbicide spray of the season. Leaving them on past mid-fall could lead to poor winter acclimation and further winter damage the next year. During winter pruning, prune off the excess suckers and consider training up one of them as a second "insurance" trunk.

When to remove the dead trunk

You can remove the dead trunk now (June) if it is not producing anything, using loppers or a saw. If the trunk is partially alive and producing a few clusters, it is acceptable to leave it there for the season and cut it down during winter pruning. The fruit may not be high quality if the vine is unhealthy, but it will help distribute some of the excess energy in the roots. 

Is Grapevine Trunk Disease Contributing to Vineyard Die-back?

There has been much discussion about the role of grapevine trunk disease (GTD) in vine die-back in the Midwest. At this point, it is not known how much GTD is contributing to winter die-back in the Midwest. Laboratory analyses are currently underway at the University of Minnesota to help determine this, but at this point it is not possible to say how much it is contributing, and it likely varies depending on the vineyard and on the overall health of the vines. Dispite contradictory claims online, trunk disease species cannot be reliably diagnosed without the help of trained plant pathologists, of whom we are currently working with on this issue. 

As a precaution, when growers cut down trunks to re-train new trunks, they may spray each pruning cut with Rally or Topsin, or apply latex paint. I recommend bringing a small backpack sprayer or handheld sprayer with these products while cutting down trunks in order to make this process more efficient. 

Photos: (top) A vine that died to the ground, with the trunk removed. One sucker should be chosen as the new trunk and trained up on a pole. (bottom) Healthy Frontenac blanc on the left and a dead block of Marquette on the right (photo credit Annie Klodd, 6/12/2019).

 

 

 

Author: Aimee Foster. A warm gentle breeze c

arries the chatter and laughter of happy wine-sipping visitors and cools us off in the miraculous 80 degree heat. We are sitting under the beautiful pavilion at Sovereign Estate Wine, a vineyard and winery in Waconia, Minnesota, where new and experienced Minnesota grape growers from near and far are gathered to learn about managing and trouble-shooting young grapevines. This is the second workshop and tour in a free series put on by the grape and enology team at the University of Minnesota.

After an introduction by Dr. Matt Clark, we walk across the lawn to visit some older Marquette vines. This picturesque block slopes gently downhill towards Lake Waconia where jet skis rip across the open water, soaking in the warm sunshine. Sheep graze the weeds in the next block over - nature’s herbicide. Here we listen to Isaac Savaryn, the vineyard manager at Sovereign Estate, talk about his pruning methods. We also discuss how bud break and shoot growth varies from region to region in Minnesota.

Next, we load up a caravan and drive to the next vineyard block. This is a newer site, planted in 2018. Annie Klodd, UMN Extension Educator, demonstrates how to shoot thin a second year vine that has been winter injured. She also demonstrates how to train two trunks on second year vines and goes into detail about the importance of training two (or more) trunks, especially in a cold climate such as Minnesota. We ask a lot out of our vines in the winter! We also discuss new site preparation, weed management for young vines, and soil and foliar testing.

Once again, we load up and caravan over to yet another new planting from 2018. Sovereign Estate is now up to about 25 acres of vineyard, one of the largest in the state. Here we discuss disease management and trellising systems.

Our last stop, quite naturally, is the tasting room. Isaac shares generous pours of the winery’s Marquette, La Crescent, and Frontenac Blanc wines as we sit at round tables and share our stories.

Thank you to all the growers who attended this workshop and added to our lively discussions. We hope to see you again!

A huge thank you to our partner, Sovereign Estate Wine, for helping to lead and organize this particular workshop and to North Central SARE for support and funding of this project.

The UMN team is partnering with Smiley Vineyard in Cannon Falls, MN for the next workshop on Saturday, June 8. They will discuss canopy management techniques and sustainable pest control. Stay tuned for a recap in a few weeks!