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By: Maria Smith and Lisa Dunlap – HCS-OSU
2026 cannot catch a break. Winter freeze injury, spring freeze injury, heat, wildfire smoke, unstoppable rainfall… and it’s still August. We are currently on track across the state for an early harvest with tough management decisions heading into the home stretch of the growing season. It has been a warm year, with about 200 to 400 higher GDD to date from the long-term average. Most notably, however, the whole state has seen above average rainfall, with central and southern half of the state receiving nearly 300% of annual monthly precipitation over a handful of days in early August (Figure 1).
Figure 1. GDD departure from 1 April to 16 August (using modified max temperature value of 86F) and 30-day percent depature of precipitation from historical average from 18 July to 16 August. Maps from https://mrcc.purdue.edu.
Current Vineyard Management Decisions (Pre-harvest)
The grapes are all well into ripening across the entire state, including Ashtabula County, which is currently about 10-14 days ahead of the 2025 growing season. With both an early ripening year and a very rainy year, routine monitoring of fruit conditions becomes even more critical. But also, as recently mentioned, disease management and PHI becomes increasingly important. The following sections will highlight some of the recent rain-related issues that we have encountered through scouting at Hort 2 and regional site visits.
As always, consult management guides and product label restrictions prior to making any pesticide application.
Downy Mildew
Despite best seasonal management of DM, it is popping out following our past couple of weeks of persistent rainfall (Figure 2). How can you manage DM close to harvest? It’s not easy, and some may elect to tolerate some foliar infections to avoid use of fungicides close to harvest. Keep in mind, though, that DM is one of the few diseases that can very quickly defoliate a canopy if left uncontrolled for the remainder of the season. Below are options and supplemental resources to help guide your decisions. More options become available during the post-harvest period to carry the foliage through to the first hard freeze.
- Captan, Phosphorus Acids, and Copper all have a 0-day PHI, however, there are many considerations to make when using low-PHI options. These include residue and potential fermentation inhibitions from Captan and Copper, fungicide tank-mix incompatibilities, and emerging DM resistance to Phos. Acids
Additional resources discussing DM and low-PHI fungicides:
- https://extension.psu.edu/veraison-to-harvest-vineyard-and-winery-considerations
- https://extension.umd.edu/resource/pre-harvest-disease-management-and-late-season-bunch-rots/
Figure 2. Recent downy mildew outbreak and active sporulation from the front (top) and back (bottom) of leaves. 24 August. Photo credit: Diane Kinney.
Powdery Mildew
In warmer regions of the state, PM is emerging as a late-season issue (Figure 3). There are more options to manage PM than DM when it comes to PHI, including the following suggestions from UMD:
- Select FRAC 3 and FRAC 7 fungicides, Quintec (FRAC 13), Vivando (FRAC U8), and Torino (FRAC U6).
Rotation is key for PM management, where excessive and repetitive use of a single FRAC code increases risk of PM resistance.
Figure 3. Powdery mildew and berry splitting in Vidal blanc. August 2026.
Late-season Rots (Sour Rot, Botrytis, Ripe Rot)
Sour rot is typically the worst of the three when it comes to rainy conditions due to berry splitting caused from excessive rainfall. Split berries provide opportunities for fruit fly and other insects that vector bacteria and wild yeasts, leading to berry discoloration and characteristic “sour” vinegar (acetic acid) aromas (Figure 4).
Botrytis infections may also arise from infections that occured earlier in the growing season during bloom or from veraison through to harvest (Figure 4). For cultivars that are highly susceptible to Botrytis, notably highly compact cluster cultivars, there are effettive cultural and chemical management options avaialble. When using Botrytis-specific fungicides, rotation is necessary to limit resistance issues.
- Conventional chemical management for sour rot is to apply one combination of low-PHI insecticides targeted for fruit flies (e.g., Mustang Maxx, Malathion) combined with peroxyacetic acid (e.g., Oxidate) at 15 brix. *Again, it should be noted that insecticide-resistance for fruit flies has been documented in neighboring states (Michigan, New York), which may contribute to sour rot control failure. Judicious use of insecticides for sour management should be practiced.
Figure 4. Botrytis (left) and sour rot (right) in Sauvignon blanc. Botytis is characterized by fuzzy gray spores, while sour rot is typically characterized by tan berries with an acetic (vinegar) odor.
When is your fruit ready to pick?
Fruit maturity
Measuring basic fruit chemistry (total soluble solids, titratable acidity, and pH) provide basic indicators of fruit maturity, yet do not tell a complete story. Flavor, seed development, and other characteristics aid in identifying peak maturity. Ripening parameters are not always a linear trend and will vary by precipitation amounts (i.e., sugar levels decrease with pulp dilution and rainfall). In some cases, sugar concentration may increase by continuing to hold the fruit on the vines post-rain, but in other instances where harvest maturity may be close, taking a risk-averse approach to harvest prior to any subsequent rain event may be preferable to avoid significant yield loss.
Other indicators may dictate that fruit should be harvested whether chemical parameters indicate full maturity. These can include “shelling” or “shatter”, where individual berries easily detach from the pedicel, and various types of berry shrivel disorders (e.g., bunch stem necrosis) that have associations with abiotic stress. In cases where overall cluster and berry conditions are a factor, fruit should be harvested to preserve yield regardless of our desire to hit certain quality thresholds. This is also where decisions in the winemaking process become integral to achieving quality wine from sub-optimal grapes.
Fruit quality and rot thresholds
Following a season characterized by frequent rainfall and elevated disease pressure, wineries may be faced with fruit containing varying levels of sour rot, Botrytis, and other bunch rots. While there is no universal threshold at which fruit should be accepted or rejected, it is important to recognize that the severity and distribution of rot can significantly impact wine quality, processing requirements, and production costs.
The decision to harvest fruit should not be based solely on soluble solids, pH, or titratable acidity. Cluster integrity, berry splitting, evidence of sour rot, and overall fruit condition must also be evaluated. In some cases, harvesting fruit slightly earlier may preserve more quality than waiting for additional ripening while disease pressure continues to increase.
From a winery perspective, the question is often not "Can wine be made from these grapes?" but rather "What level of intervention will be required to produce acceptable wine, and is that effort justified?" As rot incidence increases, the risk of elevated volatile acidity, microbial spoilage, oxidation, and fermentation difficulties also increases.
Fruit Processing Considerations
Sour rot presents challenges beyond the acetic acid already present in infected berries. The larger concern is introducing acetic acid bacteria (AAB), spoilage yeasts, and other undesirable microorganisms into the winery. Once these organisms enter the production process, they can continue to increase volatile acidity and negatively impact wine quality.
When processing compromised fruit, wineries should consider the following practices:
- Sort aggressively. Remove visibly damaged, split, or sour-rotted clusters whenever possible. This is often the most effective step for reducing microbial load and lowering the amount of preformed acetic acid entering the winery.
- Process fruit promptly. Fruit affected by rot can continue to support microbial activity after harvest. Minimize delays between picking and crushing.
- Minimize oxygen exposure. Acetic acid bacteria require oxygen for growth and metabolism. Avoid excessive fruit handling and limit exposure of crushed fruit to air. The use of carbon dioxide or nitrogen may be beneficial when feasible.
- Maintain sanitation. Equipment, bins, presses, pumps, and hoses should be properly cleaned and sanitized throughout processing to reduce opportunities for microbial contamination.
Options for juice management pre-fermentation
For fruit exhibiting signs of sour rot or elevated microbial pressure, early intervention can help reduce the risk of spoilage during fermentation.
Sulfur dioxide additions at crush remain one of the most important tools available to wineries. Potassium metabisulfite additions help suppress spoilage organisms and slow the development of additional volatile acidity. However, sulfur dioxide does not remove acetic acid already present in the fruit. The goal is microbial control rather than correction. Depending on fruit condition and juice pH, additions of 50 mg/L or greater may be appropriate for compromised fruit.
Clarification and settling can help reduce microbial populations and remove particulate matter that may harbor spoilage organisms. Where appropriate, winemakers may consider settling juice prior to inoculation to improve fermentation conditions.
Prompt yeast inoculation is strongly recommended for compromised fruit. Allowing desirable wine yeast to rapidly dominate the fermentation reduces opportunities for spoilage organisms to proliferate. Cold soaking and uninoculated fermentations generally increase risk when processing rot-affected fruit.
Nutrient management should also receive additional attention. Diseased fruit can create a less favorable environment for yeast growth, increasing the likelihood of sluggish or stuck fermentations. Monitoring and correcting YAN levels may be necessary to support a healthy fermentation.
Finally, wineries should routinely monitor volatile acidity (VA) through both sensory and analytical evaluation. Measuring VA at the completion of primary fermentation provides an important baseline for future cellar decisions.
Remember: you cannot ferment away acetic acid. The most effective strategy is preventing additional volatile acidity development through careful fruit sorting, quick processing, microbial control, and quality fermentation management.
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Links to additional OSU Factsheet Resources:
- Sour rot grapes: https://ohioline.osu.edu/factsheet/plpath-fru-50
- Powdery Mildew grapes: https://bpb-us-w2.wpmucdn.com/u.osu.edu/dist/b/28945/files/2026/08/Grape-Powdery-Mildew-Print-Version-2026.pdf
- Downy Mildew grapes: https://ohioline.osu.edu/factsheet/plpath-fru-33
Tags: 2026 Season, Enology, Juice Management
Comments: 0
By: Melanie L. Lewis Ivey, OSU-Plant Pathology
Once grape clusters reach pea-size, growers may be tempted to relax downy mildew management because the berries themselves are resistant to new infection (referred to as ontogenic or age-related resistance). But when the forecast includes rain, day after day, downy mildew deserves continued attention.
Downy mildew, caused by Plasmopara viticola, thrives under warm, wet conditions. A single rain event can create favorable conditions for infection, but multiple days of rain are especially concerning. Repeated rainfall, high humidity, cloudy conditions, and extended periods of leaf wetness can provide repeated opportunities for the disease to infect new tissue and spread throughout the canopy. When vines have little opportunity to dry between rain events, disease pressure can build rapidly.
Even after berries become resistant to infection, leaves, young shoots, and other susceptible green tissues remain at risk. This is particularly important when repeated rainfall encourages vigorous new shoot and lateral growth. That fresh, succulent tissue can be highly susceptible to downy mildew, providing the disease with new tissue to infect just as conditions become increasingly favorable.
Protecting the canopy as the berries expand is critical because healthy leaves are needed to finish ripening the crop. Severe downy mildew infections can cause premature defoliation, reducing the vine’s photosynthetic capacity at a time when the crop still needs carbohydrates to accumulate sugars and mature properly. Significant loss of foliage can slow ripening, affect fruit quality, weaken vines, and leave them less prepared for winter (i.e., more susceptible to winter injury or early season diseases like Phomopsis cane and leaf spot).
Several rainy days in a row also create challenges for disease management. Frequent rainfall can shorten the effective protection period of some fungicides, make it difficult to get equipment into the vineyard, and create narrow windows for making timely applications. If a spray is delayed while infection periods continue to occur, downy mildew can gain a foothold surprisingly quickly.
For these reasons, the berries reaching pea size should not automatically signal the end of downy mildew management, especially when the rain just keeps coming. During stretches of wet weather, growers should scout susceptible varieties carefully, monitor the leaves for symptoms and signs of disease, watch rainfall and leaf-wetness conditions, and maintain an appropriate disease-management program based on vineyard risk. During rainy periods try not to extend the spray interval beyond 10 days.
Symptoms of grape downy mildew (Plasmopara viticola) on Catawba grapevine.
Fungicide selection and timing become particularly important under sustained disease pressure. Growers should consider product efficacy, rainfastness, resistance-management guidelines, preharvest intervals, and label restrictions when planning applications. At this time of year (nearing harvest), the pre-harvest interval (PHI) is particularly important to consider. Rotating among appropriate modes of action and maintaining good spray coverage are also important components of an effective program. Consult the Ohio Grape Spray Guide or Midwest Fruit Pest Management Guide for guidance on selecting a fungicide.
Symptoms of downy mildew (Plasmopara viticola) on the upper side (yellow spots) of a Catawba grape leaf and signs of the pathogen, seen as whitish-grey areas on the underside of the same leaf.
For more information on grape downy mildew and other grape diseases contact Melanie L. Lewis Ivey, Extension Fruit Patholgist, ivey.14@osu.edu
By: Maria Smith, HCS-OSU
The growing season soldiers on and so do tasks in the vineyard. With high heat and precipitation over the past month, the vines have continued their rapid growth. We’re at the point now where hedging and skirting are necessary (Figure 1). Nearing in at > 8 ft. of growth, the shoots are folding over and shading the canopy. In southern Ohio and some of our early ripening cultivars, veraison is here already and netting should be going on for bird protection.
Figure 1. Regent shoots > 8' in length shade the fruit zone. 13 July 2026
In Wooster, we are largely about 45-50 days following bloom and are taking crop estimations for the 2026 growing season. We expect veraison to begin for most cultivars in the coming days to weeks.
For grape growers and winemakers, crop estimation is important for several reasons:
- Determining needs for fruit thinning and vine balance
- Predicting yields for fruit sales
- Estimating needs for tank space
The grape development process
Understanding the berry growth and ripening process can help understand how and when to take crop estimations.
Grape berry ripening occurs in 3 distinct phases (Figures 2 and 3):
- Berry growth – cells are dividing after flower pollination, leading to rapid growth of the berry and seeds
- Lag phase – the slow, stationary phase of berry growth
- Berry expansion and ripening – this is the period when berry growth is driven by cell expansion through the accumulation of sugar and water
While the pattern is consistent among all grapes, it is important to note that each cultivar varies in 1) when it reaches lag phase, and 2) how long lag phase will last.
Figure 2. Berry ripening curve - size and sugar accumulation. Figure from OSU Factsheet Crop Estimation of Grapes
Figure 3. Berry development in Cabernet Franc at Hort 2, Wooster, OH on 24 June 2026 (Phase I - Pea-size), 13 July 2026 (Phase II - lag-phase), and August 2024 (Phase III - Veraison - note: we have yet to reach Cab Franc Veraison in 2026)
There are several methods and models for calculating crop estimation. The two most common methods include:
- The Lag-Phase Method: This method is conducted by weighing clusters during lag-phase and doubling the weight. This relies on the principal that berry size at lag-phase is approximately 50% of the final berry weight at harvest.
2026 Yield (tons per acre) = [2 * Cluster weight at lag-phase (2026) * # vines per acre (2026) * # number of clusters per vine (2026)] / 2000
- Harvest Cluster Weight Method: This method requires the historical average cluster weight at harvest, which is used to estimate yields based on the number of clusters per vine and the number of vines per acre.
2026 Yield (tons per acre) = [Ave. historical cluster weight at harvest * # vines per acre (2026) * # clusters per vine (2026)] / 2000
Both estimates require multiplying weight (2x lag phase cluster weight or historical cluster weight at harvest) by the actual number of vines per acre and an estimate of the number of clusters per vine counted following cluster thinning (note: if not thinning, cluster counts can be obtained anytime following shoot thinning between pre-bloom to lag-phase phenology).
There are many assumptions that are pulled into methods for crop load that influence the accuracy of measurements:
- Lag phase timing is accurate for the target cultivar
- Average cluster weight is reliable for the season in which estimates occur (i.e., it is a “normal” year for fruit set)
- Final berry weight at harvest is consistent year-to-year (this gets more accurate with more years of historical data
- Missing vines are accounted for in the vineyard block when multiplying the number of vines per acre
- Sampling and representation are key: the higher the number of samples (vines and clusters) measured, the more accurate the estimates. OSU recommends a 100-cluster sample for estimated cluster weights per vineyard block. These and sampling for the number of clusters per vine should come from a minimum of 25 representative vines per acre across the block.
This year, we are choosing to weigh cluster samples at lag-phase (Figure 4) to obtain crop load estimates. This is because we have had ongoing issues related to fruit set in the past few seasons related to bloom-time weather conditions, 2,4-d drift injury affecting fruit set, and possible injury to inflorescences due to cold injury. This made using historical cluster weights unreliably over-estimate yields for our research vineyards in 2024 and 2025.
Figure 4. Cluster samples for estimating weights at lag-phase for crop estimations from Hort 2, Wooster, OH the week of July 13.
Highly cultivar-specific crop load calculators
If you have Concord, the folks at the Cornell Lake Erie Station have taken a lot of the guess work of lag-phase timing and crop estimation out for you. They have created a crop estimation calculator tool through the Efficient Vineyard website that aids in your crop estimation.
Additional resources
There are several great resources available to help with your crop estimations. Below are ones that provide cultivar-specific information to lag-phase timing in addition to using GDD-based estimations for lag-phase and more general information on crop estimations.
- Differences in Berry Growth in Cold Hardy Grape Cultivars (Iowa State) - https://www.extension.iastate.edu/commercialhort/differences-berry-growth-cold-hardy-grape-cultivars
- Timely Viticulture – Crop Estimation (UMD) - https://extension.umd.edu/resource/crop-estimation/
- HYG-1434-11 – Crop Estimation of Grapes (OSU) - https://ohiograpeweb.cfaes.ohio-state.edu/sites/grapeweb/files/imce/pdf_factsheets/Crop%20Estimation%20FS.pdf
- Between the Vines S5E6 – Concord Crop Estimation Calculator https://www.youtube.com/watch?v=WgTdLPsgdfg
- Skinkis and McLaughlin, 2022. AJEV. Pinot Noir Crop Estimation Method https://www.ajevonline.org/content/6/Suppl_1/30
By: Maria Smith, HCS-OSU
We’re halfway through the year 2026, and the rollercoaster ride has been a wild one. I have been curious for a while just how our vine phenology has been matching up with long-term changes to weather patterns, and I will put together a look at this soon. However, for the upcoming July 4th holiday, let me put it in baseball metaphor: the weather swings taken by this year have sent the ball out of the park.
Let’s take a quick glance at the weather over the first half of the growing season…
Temperatures and Growing Degree Days (Wooster)
The following figures will summarize monthly average temperature, total monthly precipitation, and growing degree days (GDD; daily average temp – base 50F), which represent heat accumulation units that correspond with phenological development of plant growth cycles.
By far, the greatest deviation in temperatures and precipitation came during April, which saw an overall average temperature deviation of nearly +7F and 3.5” of rainfall greater than the 30-year averages (Figure 1). This was particularly notable for early April, which is what drove so much rapid, early budbreak development and widespread frost damage. For growing degree days, the 30-year average for monthly GDD accumulation is 146. April 2026 accumulated a whopping 259 (+113). In contrast, April 2025 saw 159 and April 2024, our prior notable season of early budbreak, 182.
May and June snapped back and cooled down substantially compared with April, but by that point, the damage was done.
Can this pattern be related to this year’s building El Niño year? Probably. El Niño conditions officially developed earlier this month, which tends to mean, for Ohio, to expect overall cooler, wetter summer conditions, and warmer, drier winter conditions. That isn’t to say that we can’t still have punctuation marks throughout the year (!), as I write this at the start of a “heat dome” today…
What then do I anticipate for the rest of 2026? Idealistic, optimistic me says we can expect an extended fall that lends itself towards full maturation for the fruit that we do have in Ohio this season and a lovely yellowing descent into vine acclimation for this winter. Of course, I want to be balanced to the converse, which says we could be looking at managing late season fruit rots and a winter that is marked by temperature swings that cause more bud injury. But let’s set the cynicism aside for today.
Figure 1. Weather conditions (precipitation, average temperature, and GDD) from April 1 - June 28, 2026 for Hort Unit 2 in Wooster, OH. Data from https://newa.cornell.edu
Phenology
We have been moving at a good clip at Unit 2 this year, and we are currently on schedule to be approximately 1 week ahead of the 2025 growing season. Here is a look across several cultivars at Hort Unit 2 for budbreak and bloom:
Table 1: Phenology (budbreak (BB) and bloom) of key cultivars at Hort Unit 2, Wooster, OH for 2026 and 2025.
|
Cultivar |
50% BB (2026) |
GDD (Jan 1-BB 2026) |
50% Bloom (2026) |
GDD (Jan 1 - Bloom 2026) |
50% BB (2025) |
GDD (Jan 1 – BB 2025) |
50% Bloom (2025) |
GDD (Jan 1 - Bloom 2025) |
|
Cabernet Franc |
13-April |
182 |
8-June |
727 |
21-April |
134 |
13-June |
650 |
|
Chardonnay |
13-April |
182 |
6-June |
683 |
23-April |
153 |
13-June |
540 |
|
Marquette |
13-April |
182 |
1-June |
616 |
23-April |
153 |
9-June |
582 |
|
Frontenac Blanc |
13-April |
182 |
8-June |
727 |
23-April |
153 |
5-June |
512 |
|
Petite Pearl |
17-April |
264 |
1-June |
616 |
25-April |
178 |
9-June |
582 |
|
Clarion |
13-April |
182 |
1-June |
616 |
21-April |
134 |
9-June |
582 |
|
Itasca |
13-April |
182 |
1-June |
616 |
21-April |
134 |
5-June |
512 |
Bloom into fruit set:
Grapes exhibit a “double sigmoidal” growth curve, with two distinct phases of berry growth, one following fruit set (rapid cell division) and one from veraison to harvest (rapid cell expansion). We are currently in the first phase, where we have gone from flower to pea-size berries over the course of the past two weeks (Figure 2). In contrast to the 2025 season, we had overall good bloom-time weather conditions with moderate temperatures and dry conditions, leading to much better fruit set. When we reach lag-phase in a few weeks, we will be conducting crop estimates to understand how much yield we can anticipate towards harvest.
Figure 2. Chambourcin at pea-size on June 25, 2026 at Hort Unit 2, Wooster, OH.
Canopy Management
June is the peak of canopy management time, where we wrap up shoot thinning and move directly into shoot positioning, wire placement, and leaf removal (Figure 3). I’d like to take a moment to refresh a few points on leaf removal here:
Figure 3. Diane Kinney conducting leaf removal in Chardonnay at Hort Unit 2, Wooster, OH. (For those noticing the weed growth, we do in fact have weeds, contact herbicides were applied folloiwng the completion of leaf removal last week)
Leaf removal is a promoted targeted practice in Ohio to optimize sunlight exposure into the fruit zone of the canopy – it does not universally apply for every cultivar nor every training system.
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Why conduct leaf removal? It improves canopy airflow, spray penetration, and sunlight interception into the fruit zone. For the Eastern US broadly, it is a key practice for disease management. For cooler regions and seasons, it promotes increased berry phenolic development in skin (increased color, mouthfeel, and riper aromas) and improved fruit composition (more sugar, lower acid).
- Sun burn, especially under hot and high sun exposure conditions, is a major risk associated with leaf removal (Figure 4). Caution should be taken for weeks like this where, again, we’re under heat advisory conditions… Leaf removal is best performed under cooler, cloudier weather (maybe next week?)
- Traditionally, leaf removal is performed as close to fruit set as possible. This again minimizes sun burn risk. However, it’s common for that timing to extend about a month past fruit set.
-
How much canopy to expose? For red cultivars on Vertical Shoot Positioning, we typically will remove leaves on both sides of the canopy. For white cultivars or cultivars on High Wire Cordon, we may selectively remove only the leaves shaded side of the canopy (E or N sides)
Figure 4. Berry sunburn on HWC Marquette grapes following leaf removal. June 25, 2026, Hort Unit 2, Wooster, OH
Other notable issues around the state
Two major problems have arisen in the past month that have left a major imprint on the 2026 growing season:
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More auxinic herbicide drift injury. This year has been particularly bad given the short windows of dry weather for herbicide applicators. Applications have been coinciding with the slowdown in growth in May and early June that has caused major crop-loss events in several vineyards (Figure 5). Record keeping/documentation, on site weather data, and reporting are all key and timely when it comes to responding to herbicide drift injury. Timeliness is important, and complaints can be filed with ODA directly.
Figure 5. Significant 2,4-D herbicide injury pre-bloom in Vitis hybrid on May 29, 2026. -
Vine collapse (Figure 6) occurs when vascular tissue has been compromised, and the vine cannot move resources (water, nutrients, sugar) to sustain active shoot growth. This damage to the vine’s vasculature can occur through abiotic (e.g., cold injury, weedwhackers, girdling) or biotic stressors (e.g., crown gall, trunk disease).
There has been a notable amount of trunk injury (cracking, splitting) from both winter extreme lows and spring freeze stress that has been causing vine collapse this year. These injury events also contribute significantly to crown gall and trunk infections that may take time to become notable problems. Vines tend to be resilient, and while certainly demoralizing, they can usually be retrained from new growth suckers that arise from the beneath the trunk damage. This, however, may be less true for older vines that do not readily sucker. We have experienced several instances at the Wooster Vineyard where vines could not sustain additional cumulative damage and warrant replacement.
Figure 6. Early season vine collapse in Cabernet Sauvignon following winter injury, June 8, 2026, Ashtabula County, OH. Note that vine retraining can be conducted from new suckers emerging from the base of the vine that was protected with soil hilling in the fall of 2025.
By: Lisa Dunlap, OSU-HCS
This year marked my first time coordinating and directing the Ohio Wine Competition. After shadowing Todd Steiner, our former director, for several years, I thought I had a solid grasp of what I was stepping into. I quickly learned I had underestimated just how much work goes into orchestrating an event of this scale. But once the whirlwind of organizing hundreds of wines settled, the competition itself unfolded smoothly and successfully.
To offer full transparency into how this event comes together from start to finish, I wanted to share an inside look at the operations, decisions, and logistics behind the 2026 Ohio Wine Competition.
A New Host Site and New Tools
For many years, Kent State Ashtabula graciously hosted the competition. When they were unable to do so this year, we faced two options:
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Host the event through The Ohio State University Enology Extension, or
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Outsource the judging to a third party competition in another state.
OSU Enology Extension proposed a plan to host the event in Wooster, and the Ohio Grape Industries Committee (OGIC) approved it. The board also voted to adopt Enofile, a widely used wine competition management software. Both decisions were finalized on January 14, 2026.
Early Preparations: Registration, Categories, and Communication Challenges
Once approved, the first major task was registering with Enofile. Communication delays slowed progress, and setting up our competition categories proved more complex than expected. Our types of categories were not what Enofile typically handles, and I also requested an additional field to quickly identify Ohio-made wines eligible for OQW (Ohio Quality Wine seal). After several rounds of adjustments, the system became workable and clear.
Online registration went smoothly overall, with only a few wineries experiencing issues. If we continue using Enofile in future years, we plan to provide more explicit instructions to streamline the process.
Securing a Venue
Finding a hotel in Wooster that could accommodate our event and accept a temporary F3 permit was another early hurdle. Several hotels declined due to permit restrictions or insufficient event space. Ultimately, the Hilton Garden Inn proved to be the perfect fit, conveniently located across from campus wine storage, just large enough for our needs, and staffed by an incredibly friendly and supportive team. I would gladly host the competition there again.
Selecting Judges
The OGIC board approves a list of judges each year. I added several new names to the list, which the board approved. From that list, I selected 12 judges. When one judge had to withdraw shortly before the event, we secured an alternate recommended by an experienced Ohio Wine Competition judge, an excellent addition who performed exceptionally well.
Record Participation and the Mountain of Wine
Registration closed on May 1, 2026, with 59 wineries submitting 523 entries, a record number. My cooler filled rapidly until there was barely room to walk. At one point I simply stared at the stacks of boxes thinking,“What have I gotten myself into?”
Enofile assigned each wine a four-digit code. We printed labels for bottles and judges’ glasses, then organized the wines into four judging panels, each with two experienced judges and one newer judge. Panels were color-coded to match bottle and glass labels.
Sorting, labeling, and paneling the wines took roughly 50 hours. After separating samples for chemical analysis and boxing wines by panel, everything was stored until transport to the hotel.
Flighting the Wines: A Puzzle of Its Own
At the hotel, we set up four long rows of tables, one per panel, and arranged wines in flight order. While Enofile assisted with flighting, the final organization happened in Excel. This step was surprisingly challenging. Many wines were entered into incorrect categories (for example: Sauvignon Blancs listed under American grape categories, dry wines entered as sweet, Cabernet Francs placed in general dry red classes instead of their varietal class).
In total, I corrected around 128 miscategorized wines before judging began. Unfortunetly, I wasn’t able to catch all of them, but I did my best with the information given. For next year, I plan to simplify and reduce the number of categories to make registration clearer and grouping more intuitive.
Judging Days
Most judges arrived the evening before the competition. Over dinner, we reviewed procedures and prepared for a full day of tasting. Judges used the UC Davis 20-point scale and wrote detailed comments for each wine. After scoring individually, each panel discussed the wines to reach a consensus medal:
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17–20 points: Gold
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15–16 points: Silver
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13–14 points: Bronze
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12 points: Above-average commercial wine
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10–11 points: Average wine
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7–9 points: Below average
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3–6 points: Poor to very poor
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1–2 points: Undrinkable
A wine receiving unanimous gold ratings earned a Double Gold. This year, 28 wines achieved that distinction and advanced to Best of Show.
To ensure the integrity of the judging process, all wines were evaluated under strict blind tasting conditions. Judges did not have access to the section of the room where the bottled wines were stored, and at no point were they able to see labels, winery names, or identifying information for any of the samples. Wines were presented only by their assigned codes, allowing judges to focus solely on the sensory characteristics in the glass without influence from branding, reputation, or prior knowledge. The wines were poured and served by our volunteer staff members to maintain anonymity of the wines.
Best of Show
On day two, all Double Gold wines were presented to judges simultaneously. Judges evaluated each wine, discussed them by category, and then voted for their top two wines in each class. If the first-place wine in a category was not Ohio-made (which happened only once this year), the second-place wine received the Best of Ohio award.
A Judge’s Reflection
One judge captured the spirit of this year’s competition beautifully, and I highlighted a major point that was expressed by the judges this year.
“Each panel tasted about 150 wines across two days. And one thing that was clear is, good wine is good. When an exceptional wine comes across the table it demands attention and it's really a delight to experience. We had a huge variety of wines in both style and quality. There were a few heartbreaking wines that I tasted and loved what their potential was but we tasted months too early. It's an interesting thing, scoring the wine in front of me, not the wine I want to be in front of me later this year. Not every wine needs to be thought provoking, but every wine should at least be made with an attentive hand.”
-Tony Jacobson, EnoCraft
My Notes
I just want to say that I had a great time directing the competition this year. It was a learning curve, and I appreciate all of you involved for your patience and understanding this year. I believe future years will be a lot smoother. I wanted to note a few things. A consistent theme noted by judges this year was the number of wines showing signs of “bottle shock,” a temporary condition that can occur after a wine has been recently bottled, transported, or otherwise handled extensively. Bottle shock can mute aromas, flatten flavors, and make wine seem less expressive than intended. In addition, several entries appeared to be simply too young, not yet given sufficient time to integrate and develop in the bottle before evaluation. In both cases, judges were mindful to assess the wine as presented in the glass, while recognizing that some of these wines may evolve significantly over time and show much more favorably with additional aging.
I collected score sheets with any/all judges comments for each wine. I plan to go through these papers and record all notes to provide to each winery along with chemical analyses. If there are questions about medals awarded after you see the notes and the chemical analyses, we can set up times to discuss how to improve your processes. I plan to have all chemical analyses and notes recorded by the beginning of August. Medal results were sent out to the entrants shortly after the competition concluded. I apologize for sending the raw data, and I thank Christy Eckstein for providing the well-formatted version of the results this year. If you have any questions regarding the competition, please feel free to contact me. Thank you!
By: Maria Smith, HCS-OSU
2026 has been a long year, and yet it is only May. All of our fortitude is being tested, whether that is in the form of waiting out the winter polar vortex in January for the hope of primary or secondary buds to emerge this spring, or now, waiting out for any secondary buds to emerge following the past two weeks of sub-freezing temperatures with the growing season underway.
This post serves as an update to the status at Hort Unit 2 and observations from around the state with the past two weeks of spring freeze events.
It has barely been 4 weeks since we wrapped pruning at Hort Unit 2 in Wooster, and in that time, we have completed the following tasks:
- Removing our soil hills for graft union protection in Vinifera varieties
- Removing old vines for replanting
- Applying a post-emergent herbicide application of Forfeit 280 – we will be planting new vines at Hort Unit 2 and do not want to interfere with establishment from pre-emergent herbicides
- Applying a dormant application of Sulforix (sulfur-lime) following a difficult 2025 season with Phomopsis
The growing season in Wooster officially kicked off with 50% budbreak reached between April 13 – April 17 (Figure 1). For reference, this is nearly 8 to 10 days earlier than 2025 (April 21 – 23). Effectively, all cultivars broke bud around the same day this year, which deviates from our typical notion of a stratified bud break (“Early” vs. “Late”) across grape species and cultivars. However, there are still noticeable differences in developmental rates.
Rapid onset of growth the past few weeks was pushed by unseasonably warm April temperatures, which exceeded average daily temperatures from +3 to 7 F (Figure 2). Within the two-week period preceding budbreak, cumulative growing degree days (GDD; a measure of heat accumulation used for estimating plant phenological development = [(Daily max + Daily min)/2] – base 50F) were between 108 (April 1-April 13) to 186 (April 1 – April 17) for Wooster.
Figure 1. Chambourcin (top), Marquette (center), and Cabernet Franc (bottom) at Hort Unit 2, Wooster from 16 April 2026.
Figure 2. Mean temperature deviation for April 2026 (figure from climate.osu.edu)
This is now the 2nd year in recent memory (the other being 2024), where we were this early in phenological development. The problem, however, is that the median date of last freeze (28 F) remains the same (with latest dates being May 1 – May 15; Figure 3). Looking back into the OGEN archives, we have posted about the risk for spring freeze injury every single year dating back to my first spring at OSU in 2019 (7 years, for those counting). While this is clearly not a novel issue, what is novel is how early development is occurring. It’s not a couple of days, it’s weeks.
Figure 3. Median date of last 28 F (figure from mrcc.purdue.edu).
Freeze events 4/20 – 5/3
Temperatures have reached 32 F or below across different portions of Ohio for 4 nights over the past 2 weeks, April 20, April 21, May 2, and May 3 (Figure 4).
Figure 4. Minimum temperatures for 4/20-4/21 and 5/2-5/3. Figures from mrcc.purdue.edu.
At Hort Unit 2, minimum temperatures reached 29 F on April 20 and 21 and 35 F on May 2 and 3. While there was damage (Figure 5), the severity was very dependent on variety and location in the vineyard. We currently estimate anywhere between < 10% to as much as 50-60% primary shoot injury.
Figure 6. Shoot damage varied based on variety and location at Hort Unit 2 (Chambourcin - top, Marquette - center, Cabernet Franc - bottom – 21 April 2026). Shoots will take on a dark green, wilted and “wet” appearance immediately following injury and will “crisp” over the next day or so.
Thus far, most of the state has been spared significant injury over the past few weeks with damage limited to cultivars at more advanced phenological development or those that are in lower-elevational portions of sites. However, in Central and Southern, OH the damage was far more severe following the freezes from this past weekend (5/3) in part due to the advancement of shoot development over the past two weeks (Figure 5). Weather from newa.cornell.edu suggested regional temperatures between 29 to 33, depending on site-specific conditions in Central and Southeast Ohio, where most damage was reported.
Figure 6. Shoot damage in Aromella in Lancaster, OH following below freezing temperatures on 3 May 2026. Photo used with permission from K. Salyers.
Spring Frost FAQs
Over the years, we (OSU) and our regional colleagues have put out guidance following spring freeze events. The most recent guidance can be found in the following resources:
- Dami and Smith. Managing injured vines after frost – May 2023. OSU Viticulture Extension. https://ohiograpeweb.cfaes.ohio-state.edu/blog/may-1-2023-247pm/managing-injured-vines-after-frost-may-2023
- Harner. Post-freeze (4/21) Considerations. VT Viticulture Extension Program. https://vtviticulture.com/2026/04/25/post-freeze-4-21-considerations/
- Fiola. Grapevine Frost Damage II: Compensation, Management, and Potential Options. https://extension.umd.edu/resource/grapevine-frost-damage-ii-compensation-management-and-potential-options/
There are a few items that I want to highlight from this information from which I frequently receive questions.
- It is not always a given that a shoot is damaged beyond superficial injury. We earnestly experienced this with our Marquette. Even at 29 F across 2 days, our damage turned out to be relatively superficial, with shoots continuing to grow! We will wait to see how the flowers were impacted as bloom approaches in the coming month (Figure 7).
- No need to spend the time removing dead shoots. They will shed off with time and emergence of secondary shoots.
- Vines don’t typically die from spring freeze unless the temperatures are low enough to sustain vascular injury to trunks and cordons.
- Some management issues you can expect, include
- Asynchronous fruit ripening if only a percentage of primary shoots were lost
- Ripening delays from secondary shoot development
- Higher rates of vegetative growth from crop loss
- Yield loss expectations vary based on cultivar. Vinifera tend to have much lower fruitfulness on secondary shoots while many French American and cold-hardy hybrids have more fruitful secondary shoots
Remember that grapevines are perennial and continuing to manage appropriately for pests, diseases, weeds, and nutrition is critical to maintaining the long-term health of the vines.
Lastly, spring freeze is an active area of research for us in the Eastern US. We would like to hear from you if you experienced spring freeze injury over the past several weeks. A survey was put forth by our colleague, Jennifer Phillips Russo at Cornell University. If you would like to participate by sharing or updating your information, you can do so at https://cornell.ca1.qualtrics.com/jfe/form/SV_3so5iJNL5LCi13E.
Figure 7. Marquette at Hort Unit 2 with superficial freeze damage but shoot tips continue growth. 27 April 2026.
This post is an update on grapevine winter injury following an historic cold temperature streak in January 2026.
Before I get into the details on bud injury here, a reminder: We will be discussing this information in more details at the Wooster Pruning Workshop on Thursday, March 12 from 1 to 4pm at Secrest Arboretum classroom 172 garden side (2122 Williams Rd, Wooster, OH 44691. Registration to attend is required. Please register at go.osu.edu/prune2026.
Recapping Statewide January Minimum Temperatures:
Several weeks of winter cold temperatures resulted in monthly average low temperatures between 5 to10 F colder than the 30-year long-term average (Figure 1).
Figure 1. Average minimum temperature departure from the 30-year long-term average. Figure from CFAES Climate Office.
This temperature departure was driven by persistent cold temperatures over the course of 2 weeks from January 24 to 31 (Figure 2).
Figure 2. Average minimum temperature departure from 30-year long-term average values for 26 January through 1 February 2026. Figure from MRCC.
With Lake Erie achieving > 95% ice cover by the end of January, the typically winter-moderated growing regions of Northeast Ohio lost protection of lake effect conditions to buffer temperatures. The Grand River Valley and Conneaut Creek areas were particularly impacted by temperature events reaching as low as – 14.6F (Figure 3).
Figure 3. Example of minimum temperatures on 31 January 2026. Temperatures throughout Ohio dropped below 0F over the week from 24 January through 1 February 2026. Figure from MRCC.
Bud Injury – Wooster and NE Ohio:
I am going to take this opportunity to once again highlight how significant site selection is when it comes to winter minimum temperatures.
- Elevation is one of the most significant contributors to localized minimum temperatures. Cold air follows elevational changes within a vineyard site (Figure 4).
- Higher relative elevation can be several degrees warmer than lower elevational areas within the same site.
- Matching cultivar cold hardiness to site conditions is critical to bud survival and capacity to achieve a consistent yield each season.
- Site-specific information is important to understanding how weather events may impact your vineyard risks for cold injury. This is only accomplished through tracking historical weather data with an accurate and appropriately located weather station.
Figure 4. Site selection features impacting cold air drainage in vineyards. Figure from https://viticulture.uga.edu/files/2018/02/Vineyard-Frost-Protection-Extension-Bulletin_blog-share.pdf.
Armed with that information, let’s get down to the details of the damage. Over the past several weeks, our team at the Wooster Hort 2 and Kingsville AARS vineyards have been busy collecting canes from several different cultivars to assess bud injury.
Temperatures at Hort 2 in Wooster ranged between -7F at the highest elevational portion of the site (Block C) and as cold as -9.2F at the lower elevational end of the site (near Oil City Rd; approximately 20 ft of elevational difference between 3 different weather stations). Bud injury ranged between 5% (Clarion) and 36% (Teroldego; Table 1). Surprisingly, NY 06 and Frontenac blanc had higher rates of injury than I would have expected given their non-Vinifera parentage. However, the range of injury among all cultivars would be considered overall low to moderate.
Table 1. Percentage of bud injury following -7 to -9F temperatures at the Hort Unit 2 vineyard at the CFAES Wooster Campus
|
Wooster |
|
|
Variety |
Primary bud injury (%) |
|
Chambourcin |
27 |
|
Cab Franc (FPS 11) |
33 |
|
Teroldego |
36 |
|
Regent |
21 |
|
Crimson Pearl |
9 |
|
Frontenac blanc |
19 |
|
Clarion (MN 1220) |
5 |
|
NY 06 |
33 |
Temperatures in the Grand River Valley were averaged across 4 different vineyard sites. Minimum temperatures fell below 0F on 3 nights from January 24 through January 31 (Table 2). Note: temperature variation across these sites also include use of active methods for cold protection (wind machines) during radiative freeze conditions.
Table 2. Average minimum temperatures across multiple sites within the Grand River Valley for 24 January, 30 January, and 31 January 2026.
|
AVE MIN (F) 24-Jan |
AVE MIN (F) 30-Jan |
AVE MIN (F) 31-Jan |
|
-8 |
-14 |
-4.8 |
However, bud injury rates were largely consistent regardless of vineyard (Table 3).
Table 3. Percentage of bud injury across seven (7) representative vineyards in the Grand River Valley AVA (Ashtabula County, OH).
|
Vineyard Site |
|||||||
|---|---|---|---|---|---|---|---|
|
Variety |
Kingsville |
Stoltz Rd |
Rt 534 |
RT 307 (W) |
S River Rd |
RT 307 (E) |
Conneaut |
|
Cab Franc |
82 |
|
|
58 |
|
|
55 |
|
Cab Sauv |
|
54 |
66 |
71 |
|
|
58 |
|
Chamboucrin |
|
|
|
|
46 |
|
|
|
Chardonnay |
|
95 |
89 |
96 |
|
64 |
87 |
|
Merlot |
|
98 |
99 |
|
100 |
|
|
|
Pinot Gris |
77 |
|
|
|
|
55 |
|
|
Pinot Noir |
76 |
90 |
55 |
37 |
|
|
61 |
|
Regent |
15 |
|
|
|
|
|
|
|
Sauv blanc |
82 |
91 |
|
73 |
75 |
|
|
|
Saperavi |
82 |
68 |
|
84 |
|
|
|
*values indicate primary bud injury (%)
These values are based on an assessment of 100 buds per variety (10 buds per cane for 10 canes per variety). It is possible that vineyard sampling over-represents bud injury across a site. It is important to be as representative as possible and account for site-specific differences (e.g., elevation, slope aspect, etc.) within a vineyard block.
2026 Pruning Primer
Evaluating bud damage using a representative 100 bud sample per variety (or across different vineyard blocks) can inform 1) retention of buds prior to pruning to maintain yield; 2) needs for possible retraining of vines if severe vascular damage has occurred; 3) potential yield loss and crop level expectations going into the growing season.
How to dissect buds
We use a sharp, straight-edge razor (carefully!) to dissect buds along the cane by cutting approximately 1/3 of the way through the top of the bud perpendicular to the bud surface (Figures 5). For an up-close video example, we recommend checking out this YouTube clip from Hans Walter-Peterson at the Cornell Finger Lakes Program: https://www.youtube.com/watch?v=eWtr0jzI2Dk
Figure 5. Bud dissection using a straight-edge razor February 2026.
What are you looking for?
When it comes to injury, green is good (alive) and brown is bad (dead). Below are examples of grape compound buds under a dissecting scope (18x magnification). Additional photos of bud dissection can be found at through University of Missouri Extension.
Example 1. Compound bud showing the three interior buds (primary, secondary, and tertiary). Primary buds contain the largest fruit primordia (highest yield potential) and are also the largest of the three buds, followed by the secondary and tertiary (smallest, usually contains no fruit primordia). All three demonstrate green, healthy living bud tissue.
Example 2. This photo shows necrotic (brown) tissue of a dead primary bud. The color gives away bud injury in the absence of magnification. Note that the secondary bud is to the right of the primary bud in this photo due to the reversed orientation of the cane. The secondary bud sits to the bottom of the primary closest to the attachment point of the bud to the cane.
Example 3. In this photo, it is only the secondary bud that is injured. In this scenario, the primary bud is still alive, and the status does not contribute to potential reductions of yield for upcoming growing season. However, if the primary bud (or shoot) is injured in a subsequent event, only the tertiary bud remains for vegetative growth (i.e., no yield).
Adjusting bud retention during pruning
If you have not yet pruned, the following guidance can be used for yield retention following winter injury. This guidance is based on your individual percentage of primary bud injury. These recommendations are from Zabadal et al. (2008). Note that hybrid cultivars with fruitful secondary and base buds will produce a normal crop even with relatively high percentage of primary bud injury (e.g., DeChaunac, Marechal Foch, Seyval blanc, Vidal blanc).
- If primary bud damage = 0 to 14%, then no adjustment of pruning is needed.
- If primary bud damage = 15 to 34%, then leave about 35% extra buds. For example, if you prune to leave 30 buds/vine, and bud damage = 20% then leave an extra 35% or 40 buds/vine.
- If primary bud damage = 35 to 50%, then double the number of buds retained.
- If primary bud damage >50%, then it is best to minimally prune vines by hedging.
By: Maria Smith, HCS-OSU
Cold is an obvious feature of our Ohio winters, but believe it or not, this month’s sustained cold is an anomaly not seen for nearly the past century.
Although we’ve had pockets of damaging cold temperatures over the past week (Figure 1), tomorrow morning will be the most widespread and deepest of them all (Figure 2).
Figure 1. Minimum temperatures for 24 Jan 2026. Note a pocket of tempertures between -5 to -15F in far-NE OH. Temperatures at the Kingsville AARS Research Station logged -9.4F on 24 Jan 2026. Data from https://newa.cornell.edu
Figure 2. Forecast temperatures for 31 January 2026. Widespread temperatures well below 0F are expected across the state.
Current bud hardiness models are estimating temperatures for Vinifera such as Chardonnay to have attained a hardiness to nearly -16F (Figure 3). What is interesting, according to the model, is that many of our cold-hardy hybrids are estimated to have less hardiness closer to -11 to -14F (Figure 3). We will show in a follow-up post that many cultivars did lose hardiness following the warm temperatures in early January, although we would expect to regain some hardiness with the recent sustained cold weather pattern
Figure 3. Predicted LT50 (estimated minimum temepratures at which we would expect to sustain 50% primary bud mortality) for Chardonnay (left) and Frontenac (right).
Based on some initial estimates of injury following temps reaching -9.4F in Kingsville over the past week, I suspect the hardiness is likely over-estimated for Vinifera, at least. However, we will be monitoring injury rates and temperatures over the next several days and will provide more in-depth information once this sustained cold period has passed in the next week or two.
In the meantime, now is a good opportunity to review assessing grapevine winter injury prior to starting or resuming dormant pruning to determine needs for adjusted pruning and yield retention in the 2026 season.
By: Maria Smith and Diane Kinney, HCS-OSU
THIS ARTICLE SUMMARIZES THE 2025 DORMANT AND GROWING SEASON CONDITIONS AND THEIR IMPACT ON GRAPE VARIETIES GROWN AT THE RESEARCH VINEYARD OF THE CFAES-WOOSTER CAMPUS
WEATHER: TEMPERATURE
We find ourselves in a much more typical weather pattern for 2025 with regards to average monthly temperature (Figure 1). Aside from a very warm January and March, (+10 F and +5 F above long-term average, respectively), temperatures were near the long-term average. A January 21-22 polar vortex (-8 F) caused minor injury (10-15%) primary bud loss. Following this event, the season ahead looked favorable as we avoided any additional injury from spring frost. The remainder of the growing season (1 April through 31 October) remained near the long-term 30-yr average. Once again, we enjoyed a long fall with a late killing frost occurring on 10 November. Vines were able to acclimate energy and nutrient storage for the 2025-2026 winter through 207 FFD (frost free days), which were similar to the 218 FFD in 2024.
Figure 1. Temperature departure from 30-year long-term average for 1-Jan to 31-Dec 2025.
GROWING DEGREE DAYS
Growing degree days (GDD; base 50 F) was consistently ahead of the long-term average from March through October (Figure 2). Month by month, GDD fluctuated near average, with both May and August being cool but June and July warm. Our total GDD for the end of October was equal to our 30-year average (2994) for the entire year. We ended the year nearly 300 GDD units lower than 2024 with a total of 3001. 2024 was our 3rd warmest growing season in the past 10 years with 3281 GDD units.
Figure 2. Monthly GDD from 1-Jan to 31-Dec for 2025, 2024, and the 30-year long-term average
Figure 3. Cumulative GDD from 1-Jan to 31-Dec for 2025, 2024, and the 30-year long-term average
WEATHER: PRECIPITATION
2025 has been a year of two seasonal extremes regarding precipitation. Seven of those months were far below the long-term average rainfall, ranging from -0.35” to -2.64”. The remaining months had precipitation far in excess of the long-term average, reaching excesses of up to 1.27” each month. Not only was total precipitation higher, but the frequency of rain events was high. April and May recorded measurable rain for 13 and 17 days respectively, making for a very wet early growing season.
Cumulatively through July, we averaged out to be in line with our long-term average. However, August and September precipitation fell off the charts, creating late-season drought conditions. For example, August only recorded 0.65” total for the month, which is nearly 2.5” below the monthly average. This is the third consecutive year we have been well-below average rainfall, with 2025 being the least amount of cumulative rain during the growing season. By end of 2025, we are over 4” below the long-term average for cumulative precipitation (nearly identical to 2024). While excessive drought conditions negatively impact vine vegetative growth, overall, it greatly benefited fruit quality at harvest with low late-season disease pressure along with higher maturation values.
Figure 4. Annual cumulative GDD compared the 30-year long-term average from 2016 to 2025.
Figure 5. Annual cumulative precipitation compared to 30-year long-term average from 2016 to 2025.
Figure 6. Monthly precipitation deviation from 30-year long-term average.
VINEYARD NOTES
It wouldn’t be agriculture if we didn’t face some unusual obstacle, and 2025 didn’t disappoint. We were entering bud-break feeling good, having avoided a winter freeze and, later, a spring frost, only to have continuous daily rain. This is the primary conclusion we have for the uneven fruit set development experienced across the vineyard, most notably in early flowering varieties. This resulted in very poor yields across most varieties in Wooster. Therefore, for the second year in a row, when we should have been seeing beautiful fruit and abundant yields at harvest, we instead were left shaking our heads and sighing. This rain also wreaked havoc on early disease development (Phomopsis) which required continuous monitoring and short 7-day spray schedules.
- Diseases and insects: An early season Phomopsis infection period created difficult to control shoot, foliage, and fruit infections, especially in early ripening hybrid varieties. Bird pressure in the fall was extreme this year, even with timely net application prior to veraison, likely due to grapes acting as a high quality food source under fall drought conditions. Damage from yellow jackets also was notable, although did not lead to fruit rot development.
- Fruit quality: Missing or shot berries was normal this harvest season driven from both excessive early rain and rain-induced Phomopsis infections. Typically, sour rot is the leading challenge to fruit quality, and we did see some again this year but in lower incidence. We did observe ‘stuck’ fruit ripening during September when pH wasn’t ideal and TAs remained high. Fortunately, dry conditions allowed us to hang our fruit to reflect more desirable harvest parameters, but acids often still remained higher than expected.
Figure 7. Composite photo showing Phomopsis infection in vegetation (shoots, leaves) and fruit (berries, rachis) and fruit set for Verdelho (top, middle left), Cab franc (middle center), Frontenac blanc (middle right), and Itasca (bottom).
By: Amaya Atucha, Professor, University of Wisconsin Madison
As we enter the winter season, many growers are once again thinking about the risk of cold injury to grapevines. With increasingly unpredictable weather patterns, including warm spells followed by abrupt cold snaps, it often feels like we are always on alert for potential damage. During the dormant season, freeze injury to buds remains the number one concern, as even the hardiest cultivars can be vulnerable when temperatures fall below their level of cold hardiness.
There has been extensive research on how to measure and understand cold hardiness in grapevines, but the techniques we use, such as laboratory-based bud freezing assays, are not practical for growers to perform on their own. These assessments are typically carried out by researchers and extension specialists at universities and research centers. As a result, growers have had limited ways to know, in real time, how cold hardiness is changing in their own vineyards.
To address this gap, a team from the University of Wisconsin–Madison (Amaya Atucha and Al Kovaleski) partnered with colleagues at Cornell University (Jason Londo and Dan Olmstead), supported by a USDA NIFA CARE grant (2023-68008-39274), to develop a practical, grower-facing prediction tool: the Grape Cold Hardiness Risk Assessment. Built on many years of research, this tool is now available through the NEWA (Network for Environment and Weather Applications) platform and allows growers to monitor predicted cold hardiness of grapevines throughout the dormant season.
In addition to evaluating cold hardiness and helping growers anticipate winter injury risk, the Grape Cold Hardiness Risk Assessment tool can also be used when considering potential vineyard sites. By running the model for a proposed location and cultivar, such as assessing whether Cabernet Sauvignon would regularly fall below its hardiness threshold, growers can make more informed decisions about cultivar selection and site suitability before planting.
Understanding Cold Hardiness in Grapevine Buds
Cold hardiness is a vine’s ability to tolerate freezing temperatures, and it changes continually throughout the dormant season. Buds gain hardiness in the fall as temperatures cool and daylength shortens, reach their peak tolerance in midwinter, and then gradually lose hardiness during late-winter warm spells (Figure 1). Because this process is dynamic, buds can be damaged at several points in the season whenever temperatures fall below what the buds can tolerate at that time.
Figure 1. Seasonal dynamics of cold hardiness in grapevine buds, illustrating fall acclimation (progressive gains in cold tolerance), winter maintenance of maximum hardiness, and spring deacclimation (gradual loss of cold tolerance as buds resume growth).
A vine’s hardiness level is strongly linked to the temperatures it has experienced. Researchers use techniques such as differential thermal analysis to determine the LT50, the temperature at which half of the buds would be expected to die. LT50 serves as a practical threshold for injury risk and changes throughout the winter as buds acclimate and deacclimate.
Because cold hardiness is driven by temperature, weather data can be used to model and predict LT50 for many grape cultivars, including both hybrids and vinifera. These predictions help growers judge whether a cold event might cause injury, evaluate potential bud damage after a freeze, and make informed pruning and management decisions. Access to real-time hardiness estimates provides a clearer picture of winter injury risk and supports better vineyard decision-making.
How the Grape Cold Hardiness Risk Assessment Tool Works
The tool, available on the NEWA (Network for Environment and Weather Applications) platform, uses real-time or gridded weather data to estimate bud cold hardiness and identify periods when cold injury is likely for more than fifty grape cultivars.
Step 1: Choose your location
You can run the tool using either a NEWA weather station or gridded climate data.
- Using a NEWA station: Select the station closest to your vineyard and the model will automatically use current and historical weather data from that site.
- Using Grid Data: Enter the coordinates of your vineyard or proposed site. The model will use interpolated weather information from the Northeast Regional Climate Center. This option is ideal for growers without a nearby NEWA station and for evaluating vineyard establishment at new locations.
Step 2: Set model parameters
After selecting the location, choose the settings for your run.
- Choose whether you want temperatures displayed in Fahrenheit or Celsius.
- Select the date you want the model to run through. The model always begins calculations on July 1 of the current season and estimates bud cold hardiness from that date up to the selected day.
- You can choose a past date to review whether damage may have occurred.
- You can select today’s date to view current conditions.
- If your selected date includes forecasted days, the tool will project future LT50 values (temperature at which half of the dormant buds would be expected to be killed by freezing) using the available weather forecast.
- Select the grape cultivar you wish to evaluate. You can run additional cultivars by repeating this step. A downloadable dataset is also available for growers who want to store or analyze the results.
Step 3: View the results
The results panel displays a graph of predicted cold hardiness alongside weather conditions.
- The Y axis shows temperature and the X axis shows dates.
- The solid dark line represents the minimum daily temperature, and the dashed grey line represents the maximum daily temperature.
- The red dashed line labeled LT50 represents the model’s prediction of the temperature at which fifty percent of the buds would be expected to die.
- A vertical blue dashed line marks the current date within the selected period.
- If the minimum temperature line drops below the red LT50 line, this indicates that the air temperature has fallen below the freezing tolerance of the buds at that time, and cold damage is likely to have occurred.
Step 4: Review the cold damage risk forecast
The tool also provides a color coded summary of the predicted freeze risk for the date you selected.
- The risk level is displayed as Low, Medium, or High based on how predicted temperatures compare to the LT50.
- Additional dots on the panel allow you to view up to six future days of risk predictions. Selecting a dot displays the likely risk level for that day based on the weather forecast.
These features allow growers to anticipate upcoming cold events, evaluate recent ones, and make informed management decisions during the dormant season.
Grower Takeaways
- Bud cold hardiness changes throughout the dormant season and depends on the temperatures the vine has recently experienced.
- The LT50 value tells you the temperature at which fifty percent of buds would be expected to suffer cold damage.
- The Grape Cold Hardiness Risk Assessment tool predicts LT50 for more than fifty cultivars using real-time and forecasted temperature data.
- If minimum temperatures fall below the predicted LT50, bud injury is likely.
- The tool works with any NEWA weather station or with gridded climate data by entering your vineyard’s coordinates.
- Forecasted risk levels help growers anticipate upcoming cold events and plan protective actions.
- The model can also be used to assess potential new vineyard sites by comparing cultivar specific hardiness needs with the site’s temperature patterns.