Vineyard Winterization

By: Maria Smith, HCS-OSU

Semisonic’s 1998 hit, “Closing Time”, an anthem to endings, encapsulates the take-home message of this post: "every new beginning comes from some other beginning’s end." A chapter ends, and the next begins, each building on the one before. The same applies to vineyards; the success of the 2025 season begins with how we end 2024.

Over the past few weeks, I have received several calls regarding routine preparation and clean-up operations relevant to fall, which finally arrived last week in Wooster (FIG 1). Below are a few that I will highlight relevant to vineyard winterization and preparation for 2025:

Figure 1. Leaf yellowing during senescence in Vitis hybrid ‘Regent’ at Hort Unit 2, Wooster, 21 October 2024.

Q: When should I remove grow tubes?

A: Grow tubes, the blue or white cylindrical tubes placed over the vine in new vineyards (FIG 2), provide deer and herbicide protection on developing, tender new shoots. They also retain heat and moisture, which is beneficial for promoting quicker shoot development in the spring but can be detrimental for cold acclimation and wood health in the fall and winter. Grow tubes should be removed approximately one month prior to the first date of fall freeze.

Figure 2. Grow tubes installed at a new vineyard planting, June 2024.

Q: I harvested my vines, but do I still need to apply fungicides?

A: It depends. Protecting foliage through leaf fall is important for cold acclimation and maximizing winter vine hardiness, as foliage returns nutrients and carbohydrates to perennial storage tissues (roots, trunks, cordons). If your vines are harvested in August or September, and there are still months before leaf fall, then it would be prudent to continue protecting the vine foliage, especially from downy mildew, which can rapidly defoliate shoots in severe cases. Reverting to Mancozeb (at least for now) can protect foliage post-harvest and is an effective multi-site mode of action fungicide with low disease resistance potential. Mancozeb, along with other options for disease management, can be found in the Midwest Fruit Pest Management Guide. Remember, disease resistance is a key issue for powdery and downy mildew, and we should be using best practices to minimize resistance (think: combine with Mancozeb or Captan if using such fungicides as Ridomil, Ranman, Revus Top for more residual control of downy mildew)

However, if your vine varieties have low susceptibility to downy mildew, the forecast does not favor disease development (temps < 55F, dry), or the vines are very late harvest, then it’s possible that you may not require continued post-harvest fungicide use.

Q: How late is too late for sowing ground cover during new vineyard site preparation?

A: You can still sow ground cover through October into early- to mid-November (especially this year), to help stabilize soil and reduce erosion potential. One of the better options for November planting is cereal rye. Resources on cover crop options for Ohio can be found at https://cfaes.osu.edu/features/ohio-cover-crops. Choice of cover crop prior to vineyard establishment depend on your goal (soil organic matter, nitrogen, compaction, etc.) and timing of cover crop establishment.

Q: What do I need to do for fall vineyard weed control?

A: How effective is your current weed management program? For annual weed situations, contact herbicide (Rely 280, Gramoxone, Venue, etc.) application combined with a pre-emergent herbicide is effective for suppressing weeds through winter.

For perennial weed issues, Glyphosate (Round Up) is best applied at this time, since it acts systemically to kill root systems. However, glyphosate should not contact living grape tissues, as this can cause significant injury that may not be visible until growth resumes next spring. You may also consider waiting until after leaf fall to apply glyphosate. Glyphosate can similarly be combined with pre-emergent herbicides for improved weed suppression. It is important, however, that pre-emergent herbicides reach the soil surface, so earlier (now) passes of burn down/contact herbicides may be useful to clear vegetation if weed pressure was high this past year.

A note on pre-emergent herbicides: Selection should consider vine age and target weed species. For more information on grape-registered herbicides, see the herbicides section of the Midwest Fruit Pest Management Guide. Temperature and rainfall are important components of pre-emergent herbicide success, so ensure that the timing of application is appropriate based on label guidelines.

Are your soils mounded for graft union protection? This practice helps control weeds through mechanical disturbance and may mean you do not require as much reliance on herbicides as own-rooted vineyards where weeds are not mechanically disturbed. If hilling, pre-emergent herbicides should be applied after hilling has been completed.

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Winterization in Wooster vineyards is underway now that our harvest has wrapped. This also includes activities like storing netting and removing wire clips. It can also mean taking assessments of the vineyards for possible vine issues such as crown gall that could require trunk replacement in the next year (FIG 3). Now is also a good time to winterize and prepare to store your vineyard sprayer and other equipment. Lastly, now is also an excellent time to sample soils, apply lime, non-nitrogen fertilizers, or organic fertilizer sources (e.g., compost) that slowly break down over winter.

Figure 3. If foliage is not yellow in the fall, that is an indication that there may be other issues with the vine. In the case of this ‘Regent’ vine, crown gall infection is causing die back of the older cordon on the right-hand side of the vine. We will need to replace that trunk and cordon from suckers emerging from the base of this vine in 2025.