Recent Blog Posts

By: Maria Smith, HCS-OSU

May weather:

Precipitation is the story so far.

Rain is an expected feature of spring in Ohio, and that’s not much of a debate. In fact, the 30-year average cumulative precipitation for May in Wooster is 3.73”. This year, we’ve received nearly 1” above that average with 4.59” of total cumulative precipitation (https://newa.cornell.edu Wooster Hort 2 station). The real uncanny part to me is the number of days that it has rained this month: 22 of 31 days. That’s right, we logged measurable precipitation for 71% the month.

…and the fun hasn’t stopped. June to date has logged an additional 2.18” across 4 total days of rainfall so far, which is nearly 57.6% of the 30-year average monthly rainfall, with more forecast over the next 7 days.   

Temperature and Growing Degree Days (GDD)

Not only was May rainy, but it was also cool. The average daily temperature in May was 57.6 F, which is 2.6 F cooler than the 30-year average. Despite below average temperatures, cumulative annual GDD (720, base 50 F, January 1 to June 12) remains similar to, albeit slightly below, the 30-year average (787). 

Phenology

Reports across the state place phenology anywhere from pea-size (Southeast Ohio) to pre-bloom and early bloom (Northeast Ohio). 

In Wooster, we are moving through bloom this week, with some early hybrid cultivars (e.g., Itasca) near fruit set, while others (e.g., Cab Franc) are just beginning bloom (Figure 1, Table 1). 

Figure 1. Clarion approaching post-bloom (top) and Regent at trace-bloom (right). 10 June 2025. 

Table 1. 50% bloom date and GDD for select cultivars at Hort 2, Wooster, OH. 

Canopy management

With the rain and recent warming temperatures, shoots have reached nearly 3’ in length (Figure 2). Shoot and wire positioning Vinifera for VSP and suckering/thinning have been ongoing over the past several weeks. We are waiting to comb the high-wire shoots on the hybrids until the fruit starts to weigh the shoots down and shoot tips become less prone to breaking (Figure 3). 

Figure 2. Regent canopy, VSP, 10 June 2025

Figure 3. Clarion canopy, High-wire cordon, 10 June 2025.

Disease updates

Cool, rainy conditions in May meant Phomopsis in several cultivars at Unit 2 (Figure 4). In more southern regions, many are also seeing Anthracnose stem and leaf infections (Figure 5). Reminder: we are still well-within the critical window for flower and fruit protection for all major diseases. This period over the next several weeks are the most important time of the season to ensure broad spectrum coverage using your best fungicides for preventative protection. For fungicides registered for grapes and disease efficacy, see: Midwest Fruit Pest Management Guide. 

Figure 4. Phomopsis on shoots and leaves, Clarion, 27 May 2025

Figure 5. Anthracnose on Vidal blanc. Note how the lesions are gray in the center and sunken compared with Phomopsis. Leaf lesions of Anthracnose also fall out as the leaf tissue dies, leading to a “shot hole” appearance. June 2025. (Photo used with grower permission)  

Insect management

It is right about time to start turning our attention to Grape Berry Moth (GBM). This is one of the handful of insects that can cause direct crop loss from fruit damage (Figure 6). 

The other major insect to begin to start monitoring for is Japanese beetles. These foliage feeders can get out of hand quickly if allowed to accumulate large populations. 

Some minor pests to monitor for include gall makers (grape cane gallmaker, grape tumid gallmaker), flea beetle larvae, and leafhoppers. 

Scouting and monitoring (using GDD-based tools and traps) are the best means for deciding when insect control is warranted. In Wooster, we typically use fewer than 5 insecticide applications all season (this includes pre-harvest sour rot management sprays) by regular monitoring and providing well-timed and appropriate insecticide applications. Excessive use of insectcides may cause secondary pest infestations, including mites and mealybugs.  

Figure 6. Berry damage from GBM in July 2024 (and some more Phomopsis on the stem). 

Figure 7. Japanese beetle adult (top). Foliar feeding damage from Japanese beetles (bottom). July 2023. 

By: Maria Smith, HCS-OSU

While we anticipate yet another round of arctic air here in Ohio this coming week, we are forecast to be well-above the temperatures we achieved just a few weeks ago (>0F) and not expecting compounding injury from January.

For context: On 22 January 2025, we experienced one of the colder polar vortex events of recent winters, which sent temperatures plunging between -2F and -13F statewide (Figure 1).

With temperatures that cold, some damage (particularly to cold-sensitive Vinifera) is expected. However, spoiler alert, it overall was not nearly as damaging as one might expect.

Figure 1. Minimum temperatures by county on 1/22/2025. Red indicates stations from MRCC (https://mrcc.purdue.edu) and blue indicate NEWA stations (https://newa.cornell.edu). Figure by Fernanda Cohoon.

Bud Injury – Wooster

The station minimum temperatures in the cultivar evaluation blocks of Hort Unit 2 reached -8F. Below is the extent of bud injury experienced among a range of Vinifera and hybrid cultivars (Table 1).

It is important to emphasize that site selection played a critical role in the localized minimum temperatures at Hort 2. Prevailing calm winds (< 2 mph) created radiative conditions, with cold air settling in topographic depressions and lower elevations areas within the site. Across the 45 acres of Hort 2, temperatures from 3 different weather stations ranged between -8F and -10F. The Vinifera grapes (BLK C) and cold hardy hybrid trial (BLK D) are planted on the highest elevation within the site with multi-directional air drainage that inhibits cold air from pooling within the planted grape block.

Why higher mortality among Clarion (MN1220) and NY 06? The higher percentage of bud injury in Clarion (MN 1220) and NY 06 may be related to the herbicide drift injury experienced in the BLK D variety trial vines during the 2024 growing season. BLK D had the highest observed herbicide injury among all 4 planted trial blocks at Hort 2. It’s unknown, however, whether bud mortality was directly caused from herbicide injury or if the observed mortality resulted from lower hardiness and cold injury since bud dissection was not performed until after the January cold event.

Table 1. Bud injury rates of select Vinifera and hybrid cultivars at Hort 2 (Wooster, OH). Data from Fernanda Cohoon and Diane Kinney.

Bud Injury – Ashtabula

Cane samples for several standard and select cold-sensitive Vinifera varieties were collected for bud injury from AARS and commercial vineyards in Ashtabula County to assess damage over a representative range of regional conditions. Overall injury rates from Vinifera at the AARS Kingsville station and commercial vineyards from Grand River Valley (Geneva, OH) and Conneaut Creek (Conneaut, OH) ranged between 2% (AARS Pinot Noir) and 13% (AARS Sauvignon Blanc). Minimum temperatures at AARS reached -5.8F, but temperatures reported from Grand River Valley were reported to be as low as -10F.

Table 2: Overall bud injury (primary, secondary, and tertiary) among of select cultivars and sites within Ashtabula County. Data from Aaron Jaskiewicz, Patrick Turner, and Andy Kirk.

Aligning Wooster DTA information with the Bud Cold Hardiness Model Using Cabernet Franc

The cold hardiness model provided by the Londo lab at Cornell University estimated 50% bud injury for Cabernet Franc at Wooster at -16.78F (Figure 2). DTA (differential thermal analysis – a procedure to collect our own estimates of cold hardiness) from Unit 2 in mid-January estimated LT50 cold hardiness of Cab Franc FPS 11 at -16.55F, which was very close to the model-estimated -16.78F. While it’s possible that hardiness may have been over-predicted (Figure 3), Cab Franc and other Vinifera varieties were able to survive between -5 to -10F actual minimum temperatures without significant injury levels (>15%) in Northeast Ohio.

*Note: the Cornell Bud Cold Hardiness model has been integrated into the NEWA application. For an example of the output, see Figure 4. Only select cultivars are included with the NEWA model integration.   

Figure 2. Predicted cold hardiness of Cabernet Franc using Wooster, OH weather station data. Model-predicted hardiness for Jan 23 was -16.78F and an actual minimum recorded temperature for this station was -9.76F.   

Figure 3. Cabernet Franc cold hardiness data from the Geneva, NY research station that overlays DTA estimated cold hardiness with model-predicted values. LTXX lines indicate estimated temperatures at which 10 (-10.84F), 50 (-14.44F), and 90% (-18.22F) bud injury would occur. LT50 is approximately +2F less hardy than model-estimated values.

Figure 4. An example of the Grape Cold Hardiness Risk Assessment Tool using the Wooster Hort 2 weather station through NEWA.

Recommendations for bud adjustments to accommodate injury rates

We will discuss strategies for adjusted pruning and bud retention at the upcoming Wooster Pruning Workshop on Thursday, March 6.

The best course of action for managing winter cold injury is to 1) assess the amount of injury within your vineyard prior to dormant pruning using a representative sample of 100 buds (10 canes with 10 nodes per cane for each variety/vineyard block to dissect), and 2) adjust bud retention values to appropriately accommodate the amount of sustained injury for your site and varieties.

The additional number of buds to retain is relative to the percentage of damaged primary buds. The following table (Table 3) provides general guidance for how many additional buds to retain with respect to the percent of observed bud injury. Additional information on identifying bud injury and management can be found in the factsheet Assessing and Managing Winter-Damaged Grapevines Part II: Early Spring  

Table 3. Recommended bud retention adjustments based on assessed primary bud injury.

Thankfully, most damage this year thus far appears to be minimal. However, with Buckeye Chuck predicting an early spring, there is still opportunity for injury to occur moving into late winter. Though, to be fair to Chuck’s skills, he currently ranks 8^th among all prognosticating groundhogs and is only right about 55% of the time.

They say history doesn’t repeat, rather it rhymes. And right now, it’s feeling much like January 2014-2015 over here:

• Jan. 7, 2014: The term “polar vortex” enters the public lexicon with extreme damaging cold temperatures. A similar historic event would repeat Feb. 20, 2015.
• Jan. 15, 2015: OSU defeats Oregon in the first 2014 CFP national title, 42-20. 

Ten years later in 2025, OSU wins the first expanded CFP national title and this evening’s forecast tonight calls for lows throughout the state anywhere between 1F and -11F (Figure 1), with cold temperatures (< 0F) expected to persist from 8pm through 10am.

Figure 1. Forecast nighttime low temperatures Jan 22, 2025. Figure from https://weather.gov.

Some key differences from 2014-2015:

• Vine cold acclimation is much better than in 2014-2015. A late first fall freeze aided in improving winter hardiness through extending wood maturation, carbon and nutrient reassimilation. 
• Sustained below-freezing temperatures through January (Figure 2) have aided in achieving maximum cold hardiness while minimizing deacclimation and freeze/thaw cycles, which often leads to more extensive bud/tissue injury.

Figure 2. Average temperature departure from long-term mean from 22 Dec 2014 through 20 Jan 2025. Figure from https://climate.osu.edu. 

• Persistent snowpack provides an insulating layer that helps protect the base on the vine trunk.
• Our most recent estimates of LT50 (e.g., minimum temperatures that result in 50% bud injury) from cultivars at Unit 2 suggest many Vinifera cultivars have attained cold hardiness to approximately -10F and hybrids < -15F. These values are similar to reported LT50 estimates from Cornell University. 

We will be following up in the coming week with temperature minimum descriptions, incidence of bud injury, and recommendations for adjusted pruning. 

In the meantime, stay warm! 

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.