Grape Breeding and Enology | Grape Breeding and Enology

Welcome to the Grape Breeding and Enology project website

Located at the University of Minnesota-Twin Cities, we conduct research in the Department of Horticultural Science and at the Horticultural Research Center. Our focus is on grapevine cultivar development which includes: wine grapes, table grape varieties, and ornamentals that survive and thrive in cold-climate conditions. We also work on understanding the mechanisms of disease and pest resistance so that we can incorporate these traits as a way to improve sustainability for Minnesota growers. In addition to breeding grapes, we develop and teach enology best practices for cold-hardy grapes.

Ask for Clarion!

By Kate Fessler, Drew Horton, John Thull, and Matt Clark

We have developed a short guide for our most recent UMN release, 'Clarion'! This high quality white wine cultivar is hardy to USDA Zone 5. Click on the preview below to open the PDF, or at the following link: Link to Clarion fact sheet.

Image of the first page of the Clarion fact sheet

News

Early Season Control of Phomopsis on Grapes

April 8, 2019

Author: Annie Klodd, Extension Educator

Phomopsis is a prevalent grape disease in Minnesota, and should be sprayed for as part of your early season spray program between bud break and pre-bloom stages. If uncontrolled, it causes brown and black lesions on the canes, black/yellow spots on the leaves, and rot on the ripe berries that can lead to weaker plants and yield loss. Below are some key tips for managing phomopsis:

1) Your timing is important: Spray for phomopsis between bud break and bloom after wet weather, typically 1-3 times. Phomopsis disease spores overwinter on last year's canes and woody tissue. In the spring once conditions are right, the spores are released and spread to new shoots and leaves via rain drops. Infection requires at least 6 hours of leaf wetness, and ideal temperatures are between 60-68 degrees. Since these weather conditions are common in the spring, it is usually necessary to spray at least once.

2) Once a shoot is infected, symptoms do not appear immediately. Symptoms of the infection become visible on the leaves a few days after the infection, and on the canes 3-4 weeks after infection. The fungus will lay dormant on the berries until veraison, so symptoms will not be visible until after veraison. In other words, symptoms you see during harvest probably happened during bloom and needed to be treated weeks earlier. By the time the fruit is beginning to rot, it is too late to treat effectively.

3) The following products have effectiveness on phomopsis: Captan (very effective), Mancozeb (very effective), Ziram (moderate), and Pristine (moderate). Apply one or more of those products at bud break, before the shoots are 4 inches, especially if the conditions are right for the fungi to spread (see #1). Do another application when the shoots are between 4-10 inches, and again pre-bloom if needed (weather-depending). Mancozeb, Ziram, and Pristine also control black rot.

Mancozeb: REI 24h, PHI 66 days. High effectiveness on Phomopsis, anthracnose, black rot, and downy mildew
Captan: REI 72h, PHI 0 days. High effectiveness on Phomopsis and downy mildew. Moderate effectiveness on anthracnose.
Ziram: REI 48h, PHI 10 days. High effectiveness on black rot. Moderate effectiveness on phomopsis, anthracnose, and downy mildew.
Pristine: REI 12h*, PHI 14 days. High effectiveness on anthracnose, black rot, downy mildew, and powdery mildew. Moderate effectiveness on phomopsis and botrytis bunch rot.

*Pristine's REI becomes 5 days if you are doing shoot positioning.

4) As much as possible, determine the timing of your sprays based on when weather conditions are right for phomopsis infection. If your work schedule is flexible, do not rely on a "calendar spray" for diseases or insects in general. It is much more effective to spray based on plant growth stage, weather, scouting, and knowing how much infection you have had in past years. If weather has been dry and warm since your last spray, the phomopsis spores are not likely active. If weather has been cool and wet, spraying becomes more necessary because spores have likely spread.

5) Prune out canes that have black lesions on them (See photo above, and in Ohio Sate page below) and remove or destroy them.

Resources:

Tips for Reducing Grapevine Trunk Disease During Pruning

April 2, 2019

Many growers have been inquiring about what they can do during pruning to manage grapevine trunk disease (GTD). Below are a few general tips to reducing the risk or prevalence of grapevine trunk disease. They can be adapted to the individual vineyard based on what is feasible within your management system.

Grapevine wood with trunk disease staining

1) Remove and replace any cordons that are not productive. If the cordon is as thick as the trunk, on a mature vine, and it has been declining in productivity, it is time for it to go; it will only continue to decline. Furthermore, if more than 1/2 of the length of the cordon is not producing spurs, it can be replaced. Lack of productivity on a cordon can be a sign of either trunk disease or winter injury, or both. But either way, the cordon is not as productive as it could be and may be harboring disease.

To replace a cordon, tie down a healthy replacement cane over it and remove the old one either this year or next year, depending on its level of die-back. For instance, if it is mostly not producing, there is no need to keep it; cut it out this year. However if you wish to harvest some fruit off of it this year, keep it and remove it next year. This method will help remove a good amount of diseased wood if it is present, and will make sure disease does not spread from the cordon to the trunk.

2) Remove pruning cuttings from the field, rather than leaving them on the vineyard floor. This is especially if the cuttings have visible disease symptoms on them, like discolored interior wood or black lesions. This can, and is, done successfully in Minnesota. It can be done with a bobcat, or with a trailer behind a 4-wheeler. Once removed, cuttings can be burned in a pile.

3) When cutting down a trunk or a cordon that has died, dab that wound with latex paint, and/or spot spray it with a fungicide that has some surface-level efficacy on trunk disease spores such as Topsin or Rally. This can be done with a handheld or backpack sprayer. Then, come back again a few days later and dab the wound with latex paint to seal it up from incoming spores. This is only effective on the surface of the wound - it will not effect fungal infection that is already established in the wood. This tip is based on research in warmer areas, and has not yet been researched in our Minnesota climate.

4) Next year, consider pruning earlier in the season (Feb-March), rather than starting in late March or April. This is easier said that done in years when there are 2.5 feet of snow on the ground, like this year. But there is good, consistent data out of several areas of the US showing that if temperatures remain below freezing for several weeks after pruning, it drastically reduces the risk of GTD to infect the pruning wounds. This is because the wounds have an opportunity to dry and harden before the fungal spores become active in the spring, therefore they cannot infect the dried up wounds.

5) Check your cordons for interior disease symptoms when pruning, and save those samples so that our team can analyze them for trunk disease. Grapevine trunk disease appears as brown discoloration in the wood. On green wood, it more often appears as black discoloration.

I know of at least two Minnesota growers who plan to try spraying their entire vineyard with Rally or Topsin to control GTD, based on recommendations from warmer wine regions. If you do this, be aware that you are doing it experimentally; we do not yet know the best timing or effectiveness of this treatment in Minnesota, when there is often a long time period between when we prune and when we can spray. The recommendations from other regions say to spray immediately after pruning if you are pruning when the spores are active (above 35 degrees consistently), and then repeat the spray one or two times during pruning and bud break. If the ground is saturated or snow-covered and you cannot get the tractor into the field, you may miss this critical time period. As part of our 2019-2021 research into grapevine trunk disease, we hope to determine the best time frames for spraying based on when the spores become active in Minnesota.

For questions about grapevine trunk disease in Minnesota, contact Annie Klodd at [email protected]