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By: Maria Smith, HCS-OSU

In Wooster and throughout much of Ohio, we’re here: veraison (Fig. 1), the onset of the ripening period. During veraison, the berries will begin to change color, soften in texture, and expand in size. This is also the time when grower efforts earlier in the season will pay off in yield and quality outcomes of the mature grapes. Today in Wooster also marks our first harvest of the season with very early ripening Brianna (Fig. 1).

Once again, our program is providing weekly cultivar maturity updates through OGEN. These updates can be found on the front page of the OSU Buckeye Appellation website.

A bunch of grapes on a vine

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Figure 1. Marquette at veraison (left) 3 August 2023 in central OH and Brianna at harvest (right) 21 August 2023. Brianna photo from Diane Kinney, Wooster Unit 2.


Growing degree days: As of August 20, we are at 2,074 GDD (Fig. 2). This is still below the long-term average (2,271). If we continue along the current trajectory, this will be the coolest season we have had in Wooster in the last 6 years.

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Figure 2. Wooster, OH cumulative GDD (base 50F) as of August 20 = 2,074, historic GDD for August 20 = 2,271. Chart from CFAES Weather System (

Precipitation: Although rain picked up in June, precipitation continues to be below or near average for July and August. Precipitation for July was 2.5” and 3.7” to-date for August. The long-term averages are 4.1” and 3.1” inches for July and August, respectively. Cumulative precipitation for the 2023 growing season (1-Apr through 20-Aug) is approximately 4” below the long-term average (18.7”).

Disease and Insects:


  • Midseason: When rain events resumed in late June/early July, so did disease infections. While many canopies were looking very clean during bloom, failure to continue protecting developing berries during the 4 to 5-week post-bloom period may now start to make an appearance. This has been most observed for black rot and anthracnose, which have begun appearing in infected fruit over the past few weeks (Fig. 3). Unfortunately, once infection symptoms appear in fruit, they cannot be retroactively treated. Vineyard sanitation practices to remove and destroy mummified berries and clusters should be performed to reduce black rot inoculum for the next season. Unlike previous seasons, downy mildew (DM) has not been as prevalent of an issue this year.
  • Pre-harvest: Weather (temperature, precipitation) and canopy microclimate are major determinants of pre-harvest diseases, particularly bunch rots (sour rot, Botrytis, ripe rot) and foliar downy mildew. Skipping out on a protective spray at veraison may cause several of these diseases to pop up unexpectedly once grapes begin reaching 15+ Brix in susceptible cultivars. Keep in mind, following veraison low-PHI fungicides and those without adverse effects on fermentation should be used. A few examples include Captan, Phosphrous acids (Rampart, ProPhyt, Phostrol), OSO 5%, and Oxidate. Always consult the label for PHIs.
  • For more disease-specific resources, see:


Figure 3. Black rot in Chambourcin (left) and Anthracnose in Vidal blanc (right).  


  • Midseason: Japanese beetles, emerging in early July, are finally subsiding. Some feeding damage was observed in shoot tips during July, but control using Carbaryl (Sevin XLR) prevented severe defoliation (Fig. 4). 
  • Pre-harvest: Several insect species can be problematic during grape ripening, especially wasps, fruit flies, brown marmorated stink bugs, and multi-colored lady Asian beetles, which can all negatively impact fruit and wine quality.


Figure 4. Japanese beetles (left) and leaf skeletonization of new cordon (right).

July Phytotoxicity: Many pesticides can cause phytotoxicity, depending on tank mix compatibility, cultivar sensitivity to active ingredients, and vineyard conditions (temperature, leaf wetness). Captan, in particular, can cause foliar burn and scarring on green berries when applied in conjunction with other pesticides that contain oil.

This year we have noticed difenoconazole, an active ingredient in Revus Top and Inspire Super to cause foliar phytotoxicity in UMN cold hardy cultivars at several vineyard sites. This was observed in commercial plantings of La Crescent and Frontenac, and in unreleased trials of UMN cultivars at Unit 2 in Wooster (Fig 5). 

Berry splitting and bruising: I will be putting out a second blog post that discusses the various causes of berry splitting, bruising, and scarring. However, it has been observed in several vineyards throughout the state from various causes including hail and phytotoxicity. In some cases, damaged berries may shrivel up and be unproblematic, while in others the damaged berries may become a source for late-season bunch rot infections.

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Figure 5. Difenoconazole injury and berry splitting in MN 1241. August 2, 2023. Photo from Diane Kinney.

Cultural management and harvest decisions:

  • Crop estimation. Mid-season crop estimation provides a good indication of final yield, which can be used to assist winemakers with volume estimates or with the amount of grapes available to sell. Crop estimation is best done at lag-phase, which may still be ongoing in late-ripening cultivars or in cooler regions of the state. 
  • Veraison nutrient management. Verasion is the last time during the growing season that vine nutrition should be adjusted and is the optimal time to check for most nutrients. Veraison adjustments using low-dose (5 lbs N/acre) applications of nitrogen may increase yeast assimilable nitrogen (YAN) in fruit with low N-availability without excessive increases in vegetative growth (Gutierrez-Gamboa 2022, Tian 2022).
  • Crop thinning. Although major yield adjustments are best made from pea-size to bunch-closure, removing green clusters that lag behind ripening fruit during version can help in producing uniform fruit at harvest. Given the late spring frost in May, it is a good year to evaluate fruit uniformity and make the decision to either drop green clusters or possibly consider a second harvest of late-emerging secondary clusters.
Posted In: Viticulture
Tags: 2023 season
Comments: 0

By: Maria Smith, HCS-OSU

This past month in the vineyard can be summarized by a few words: cool, dry, hazy. Phenological development has proceeded slowly, with early cultivars beginning bloom only 2 weeks following the last freeze event and some still moving through as recently as last 21 June (Fig 1). In part to primary shoot loss from the multiple rounds of April and May freeze, it is reasonable for there to be high variability in phenology and ripening this year – particularly among French American hybrid and Riparia (MN) cold hardy cultivars with fruitful secondary shoots. At this point in the season, it’s important to begin taking stock of yield potential and make determinations for crop adjustments. Fine-tuning crop levels can be made through cluster thinning between pea-size to bunch closer stages (Fig. 2) of those highly fruitful cultivars to aid in accelerating ripening and managing crop loads of damaged vines. For Vinifera with extensive frost injury, excessive vegetative growth in response to low yields may require adjustments to vineyard fertilization, shoot positioning, and hedging to maintain healthy vegetation and provide sunlight exposure to developing buds.

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Fig 1. (Top) Bloom beginning in the cold-hardy hybrid trial block at Wooster Unit 2, 30 May 2023, (Bottom) Cabernet Franc completing bloom at Wooster Unit 2 21 June 2023.  

Fig 2. Example of clusters approaching bunch closure in ‘Brianna’, Wooster Unit 2, 21 June 2023.

Weather Update

Growing degree days: As of yesterday (June 29), we are at 977 GDD, which is below the long-term average (1148; Fig 3) and less than where we were this same time in 2022 (1256).


Figure 3. Wooster, OH cumulative GDD (base 50F) as of June 29 = 977, historic GDD for June 29 = 1148. Chart from CFAES Weather System (

Precipitation: Dry conditions continued throughout the first half of June, with only one measurable rainfall between May 14 through June 11. Rain has been much more frequent since then, with Wooster receiving 3.05” during the last 2 weeks of June. Despite our recent rains, we are still below the 10-year average June rainfall of 4.35”. As of yesterday, much of Ohio is still registering within abnormally dry to moderate drought conditions (Fig. 3). I have yet to see any signs of drought stress from commercial vineyards with mature vines. But, as I mentioned in May, persistently dry conditions will adversely affect establishment of newly planted vines, and irrigation should be ongoing when soil is dry.

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Fig 3. Ohio drought status, 27 June 2023. From

Disease management

Thanks to the low precipitation and cool temperatures in May and early June, disease pressure has been low. That bodes well for clean fruit and canopies moving through bloom into early fruit set. However, with the increase in rain frequency and the forecast for warmer temperatures and humidity moving into July, we should not sleep on our spray schedules. Remember: The critical period for fruit infection is pre-bloom through 5 weeks post-fruit set. This goes for Phomopsis, anthracnose, black rot, downy mildew, and powdery mildew. Other “late season” diseases, such as Botrytis and ripe rot, can also infect during bloom (Botrytis) and berry development (ripe rot). Several resources for disease management and designing spray programs was linked in the May 2023 Vineyard Updates. There is one more addition to that set of links from Dr. Katie Gold at Cornell University: Grape Disease Control, June 2023

Fig 4. New black rot lesions following mid-June rain events, June 2023.

Insect management

Regular scouting and monitoring GDD from pre-bloom through early fruit set is important for timing control sprays for grape berry moth and foliar phylloxera. These two insects can cause extensive damage if not managed.

Grape mealybug has also been reported in several vineyards over the past month. In addition to cosmetic damage, mealybugs are known vectors for grapevine leafroll virus, which is considered a major problem for Vinifera cultivars.

Minor pests, including various gall makers and grapevine aphids, are beginning to show up. These insects do not typically occur in high enough populations to represent major threats to vine health, yield, or fruit quality, thus do not require targeted control.

Japanese Beetles (Fig. 5) will begin to grace us with their presence over the next several weeks into July. I started seeing the first adult JB in NE Ohio last week.

Available chemical options and efficacy for insect control can be found in the Midwest Fruit Pest Management Guide.

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Fig. 5 Japanese beetles skeletonizing leaves on 'Traminette', Wooster Unit 2, July 2021.

Air Quality

I never really thought I’d be talking about smoke taint in Ohio, but here we are. Air quality this past week has been awful, reaching nearly hazardous conditions of 300 in Wooster on Wednesday (Fig. 6). This is the second week in June that AQI has breached unhealthy levels, and with the ongoing wildfires in Canada, it’s projected to be an ongoing issue throughout the remainder of the summer. Does this mean that your grapes will have smoke taint? The short answer is that we don’t yet. Predicting smoke taint is difficult, and phenological timing matters with exposure being more consequential between veraision and harvest. Let’s hope that when we reach ripening the air will be clean!

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Fig. 6 Air quality from 28 June 2023. Figure from

Posted In: Viticulture
Tags: 2023 season
Comments: 0

By: Imed Dami and Maria Smith, HCS-OSU

Freeze advisories were issued the week of May 15 and temperature dropped below freezing on May 18. The lowest temperatures ranged between 28 oF and 31 oF. These freeze events were thankfully not widespread and occurred mainly in northeast Ohio (see map below). Note that this was the latest freeze since 26 May 2013 for Wooster and the second latest freeze on record since 1997. 

At the time of freeze occurrence, stages of development in grapevines ranged between 3” and 12” shoot growth. Expected killing temperatures at those stages vary between 29 oF and 30 oF. Therefore, shoot injury was sustained in some vineyards. Overall, damage was sporadic and reported in only few vineyards that have less than ideal site locations or have varieties that budded out very early.  Those who have wind machines turned them on in northeast Ohio. At our research vineyard in Wooster, budbreak took place mid- to late April; however, temperature dropped to only 35 ºF on May 18. Several growers reported minimum injury to Dr. Smith. For those who experienced damage, they may refer to a previous article posted by Dr. Smith that discusses how to deal with injured vines.

We assume that we’re done with cold events between winter and spring for now, and we hope not to worry about it until next year.  

Posted In: Viticulture
Tags: 2023 season, Spring Frost
Comments: 0

By: Maria Smith, HCS-OSU

With the frost risks largely in the rear-view of April, we are starting to see new shoot growth bolt ahead under warming temperatures of the past week (Figure 1). Keep in mind, if you did have damage from those late-April freeze events, you may just be starting to see the emergence of secondary and tertiary shoots (Figure 2).


Figure 1. Shoot growth Chardonnay 4-May 2023 (top) at E-L stages 3-4 and 16-May 2023 (bottom) at E-L stages 11-12.

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Figure 2. Primary and secondary shoot emergence from single node position


Cumulative GDD in Wooster is near the historic average for this time of year (Figure 3) as warm early- and mid-April temperaturs have been buffered with a cool down in late-April through early-May. As mentioned in the last post, we saw two late spring frost events that contributed to wide-spread injury to many vineyards in the northern portions of the state.

April precipitation (4.0”) was 0.6” above the 10-year average rainfall (3.4”), but we are currently on track for a drier than average May, with only 1.3” of accumulated rainfall in the first 2 weeks of the month.

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Figure 3. Wooster, OH cumulative GDD (base 50F) as of May 16 = 372, historic GDD for May 16 = 383. Chart from CFAES Weather System (

Timely vineyard management:

Below are some considerations for cultural management of your vines at this early stage of the growing season:

  • New vineyard plantings: Now through early June is when we need to get our new vineyard plantings completed. If dry weather persists, new vines should be irrigated. 1 and 2-yr-old vines should receive around 0.5” to 1” of water per week through rainfall and irrigation while root systems are being established.
  • 2 and 3-yr-old vines: retain the 2-3 shoots required for continued trunk and/or cordon establishment and remove the remaining shoots from the trunk. Remove inflorescences (flower clusters) from the remaining shoots. The goal of these tasks is to encourgage robust vegetative growth of young vines.
  • Mature vines: Shoot thin vines when shoots are between 6-12” in growth. For details on shoot thinning and suckering mature vines, visit our blog post from May 2022 and review our video on canopy management here. *Note: shoot thinning for vines that were adjusted for bud counts following winter injury is critical, as canopies will be denser with greater bud retention.
  • The process of de-hilling soil around grafted vines should be completed to prevent scion rooting

Disease management

With the rapid rate of shoot growth along with the increase of average daily temperatures, it’s important to ensure your shoots stay protected against early season diseases, including Phomopsis, Anthracnose, Black Rot, Downy Mildew, and Powdery Mildew. Remember that disease management should be preventative beginning around 1” of shoot growth and combined with best canopy management practices.  

For successful control, it’s important to understand the disease, cultivar susceptibility, and management options. There are several resources available for disease management such as the Midwest Fruit Pest Management Guide, Developing an Effective Fungicide Spray Program for Grapes in Ohio, and NY/PA Pest Management Guide. Fact sheets on important grape diseases can be found here. Read and follow all label guidelines and ensure proper fungicide rotation and sprayer coverage/calibration to reduce risks for fungicide resistance.

Vineyard insects

During the warm stretch of April, I was hearing from several growers about the prevalence of grape flea beetles in vineyards seen brazenly snacking on swollen buds. Adult beetle damage to newly developing buds can be economically damaging to yield if not adequately controlled. Flea beetles tend to be most concentrated along vineyard boarders in proximity to wood lines, so treatment may only need to be targeted in certain portions of the vineyard. Thresholds for spraying flea beetle have been suggested at 2 to 4% (or 2 to 4 injured buds per 100 buds checked), and broad-spectrum insecticides work well against flea beetles if necessary to use. Be aware that flea beetles go through one lifecycle per season and that their larvae can cause damage and skeletonization to leaves through June (though rarely in sufficient quantity to be considered economically important), and control of larvae may help reduce future populations of this insect.

Herbicide drift injury

Rapid shoot growth in vineyards generally coincides with planting time for row crops, and with that comes the risk for herbicide drift injury. The most effective way to reduce the risk for herbicide drift injury is to develop relationships with neighboring farmers and applicators and inform them about the proximity of your vineyard. However, drift injury may still happen, and it’s best to be prepared since drift events are sporadic and difficult to predict.  

An early, subtle symptom of auxinic herbicide (2,4-D, dicamba, etc.) injury is shoot epinasty, which can be mistaken for other abiotic stresses like drought (Figure 4). Other symptoms including leaf cupping, curling, and chlorosis (leaf yellowing) may take additional time to develop and depend on the amount of herbicide exposure (Figure 5).

If you suspect your vineyard has experienced an herbicide drift event, document your evidence as soon as possible and consider taking action by contacting the Ohio Department of Agriculture to file a complaint.

Figure 4. Shoot epinasty, or the downward growth of shoot tips. 48-hrs following low-concentration herbicide exposure.

Figure 5. Leaf cupping patterns 48-hrs following high-concentration dicamba exposure.

Posted In: Viticulture
Tags: 2023 season, Vineyard Update
Comments: 0

By: Imed Dami and Maria Smith, HCS-OSU

Statewide frost events occurred on April 24-27 (Table 1). Early budding varieties had already broken buds or were at a more advanced shoot development, and thus sustained frost damage. At the OSU research vineyard in Wooster, temperatures in a shielded logger at 5ft high measured 32F on April 25 and 34F on April 27. However, when we measured the temperatures in proximity to the fruiting spurs, we recorded temperature between 27.5 °F and 30.2 °F, i.e., below freezing. As a result, frost injury was minimal, causing only burning of leaf margins (Figure 1).   

Table 1. Ohio regional minimum temperatures (°F) from 25 April and 27 April. Weather data from CFAES Weather System and NEWA

Weather Station

25 April min temps (°F)

27 April min temps (°F)

Ashtabula (Northeast)



Avon Lake (North Central)



Caldwell (Southeast)



Cincinnati (Southwest)



Columbus (Central)



Fremont (Northwest)



Piketon (Southcentral)



Wooster (Northeast)




Figure 1. Leaf margins burned after a frost event, bus the shoot is still alive (photo by Dami).

Factors affecting frost injury:

Phenological (developmental) stage: During deacclimation (March-April), grapevines become increasingly sensitive to temperature below freezing (32 oF) and critical temperatures (CT) vary with the stage of bud development. That is, buds become more sensitive as they grow in early spring. CT of buds or young shoots is defined as the air temperature that causes 50% damage after exposure for 30 minutes. The following is an example of CT of Pinot noir at different stages of bud/shoot development:

Stage of development

Critical Temperature (CT)




Dormant bud



Swollen bud stage



Bud burst (break)



First unfolded leaf



Second unfolded leaf



Fourth unfolded leaf



Weather conditions: CT also varies with weather conditions including air relative humidity and corresponding dew point. Dew point (DP) is the temperature at which water condenses out of the air as dew or the temperature that corresponds to 100% relative humidity.  Condensation releases heat and slows the drop of air temperature. Thus, if DP is higher than CT, heat will be released before reaching damaging temperatures and may provide some protection.  If the air is dry, DP is low and temperature will drop rapidly and may reach CT and thus cause more damage. 

Early budding varieties are also more susceptible to spring frost. For example, Marquette, La Crescent, Concord, Chardonnay break buds early in Ohio and thus tend to be sensitive to spring frost. Late budding varieties such as Vidal rarely sustain frost damage. Further, varieties bear fruit on shoots originated from primary buds. Some bear fruit from secondary and base buds. Secondary and base buds of Vinifera and Native grapes are not as fruitful and thus may sustain more crop loss than Hybrids. Secondary buds may produce 30-50% of the crop potential. Tertiary buds typically are not fruitful regardless of variety.

Figure 2. Frosted shoot and new shoot emergence from spur base bud (Archive photo by Dami)

What to do after a frost event?

  • First, do not give up! Grapevines have an amazing way of recovering and compensating for yield. Also, the percent of damage does not equate the percent of crop loss.
  • Whether the damage is severe or not, you should not discontinue your disease and insect management program. You need to keep the vine canopy healthy.
  •  Fertilization: if the damage is severe and only fruitless shoots recovered, this situation may lead to excessive shoot growth and vigor. You should avoid nitrogen fertilization. If the damage is minimum and a normal crop is expected, continue a normal fertilizer program. If you practice split application of nitrogen (N), skip the first one and then, based on the fruit to shoot growth, decide whether to apply the post-fruit set N application. 
  • Canopy management: due to excessive foliage and resulting shading you may need to be more aggressive with your canopy management practices. This practice will vary with the level of frost damage and variety. Like any other vineyard operation, it comes down to practice cost and the “well-being” of the grapevine. Sometime, the two factors do not go together. It is up to the grower to decide which way to proceed. Since there are many scenarios to consider that are dependent on the type of frost damage (partial or complete) and variety.
  • Provided below are two specific examples of canopy management based on reported research in Indiana and California.
    1. Our colleague, Dr. Bruce Bordelon at Purdue University, conducted a trial to manage several hybrids after a frost event that caused partial frost damage. Damaged shoots were either pruned (shoot or spur) or left intact (untreated control). With Marquette, pruning damaged shoots resulted in increased yield and better cane quality (size) the following year.
    2. Glenn McGourty, past OGWC speaker and viticulturist at UC Davis, conducted a similar trial with Chardonnay. He also found that removal of damaged shoots resulted in higher yield. Fruit ripening was delayed, but fruit quality was unaffected. In both situations, there was added labor to remove damaged shoots (20 to 30 hrs/acre). However, the extra cost in the year of frost damage was justified with less labor for pruning the following season and better cane quality. Basically, a severe frost year was a good year to “clean up” old cordons for new spur development. If you have a specific situation and undecided how to proceed, please do not hesitate to contact me.   
  • Disaster Assistance: Contact your local USDA-FSA (Farm Service Agency) and report your crop loss. It is important that you record the extent of damage you have, in case some assistance program becomes available.



Posted In: Viticulture
Tags: 2023 season, Spring Frost
Comments: 0

By: Maria Smith, HCS-OSU

It sure does feel like March Madness, especially with the recent arrival of Ohio’s infamous “second winter”. Thankfully, the cooldown from February’s warm, spring-inspired weather will help us keep the vines asleep a little bit longer. This cooldown should help us complete this most important dormant-season activity: pruning. As a follow up to last week's pruning workshop, let’s go down the reminders of when, what, and whys of pruning.

Why prune?

In young vines (< 3yo), pruning is intended to build the vine to conform to the intended training system. This means, selecting healthy wood for trunk and/or cordon establishment.

For mature vines (>3 yo), the main goal of pruning is to adjust the vine size and yield potential to produce a healthy crop in the upcoming season (i.e., create a balanced vine). For new grape growers, this seems dramatic, but in “normal” years, this means removing more than 90% of the 1 yo wood that is on the vine (Fig 1).

Figure 1. Vine before pruning (left) and after pruning (right). High wire, bilateral cordon-trained Vitis hybrid.

What to prune? Or how many buds to retain?

Normally, we suggest a method called “balanced pruning”, or retaining bud numbers according to vine size based on the pruning weight of 1-year-old canes.

Table 1. Balanced pruning formulas for different grape types. Adapted from Midwest Grape Production Guide. The formula follows the number of buds to leave for the 1 lb of pruning weight + the number for each additional lb of pruning weight.



Pruning Formula

Cluster Thinning


30 + 10


French Hybrids

20 + 10


New Hybrids

20 + 20


Seedless Table

30 + 10



20 + 20

Yes / No


A general rule of thumb: this should equate to approximately 4-6 buds per foot of vine spacing (e.g., if the vine spacing is 5-8’, retain 20-50 buds per vine). *Note, buds on hybrid and Vinifera wine grape varieties are typically more fruitful on the basal nodes. Therefore, when retaining buds, it is often best to leave more 2-3 bud spurs instead of fewer, longer spurs. This is not the case with Concord, Niagara, and other American varieties where the most fruitful buds are nodes 3-6.

But winter 2022-2023 wasn’t “normal”. The Christmas Eve polar vortex may have caused significant bud injury to your vines, especially in the most cold-sensitive varieties or in the colder locations in the state (see: Pre-Christmas Freeze and Impact on Grapevines). In Ohio where we have a propensity for winter injury, it’s important to check your bud injury and adjust pruning accordingly to maintain cropping levels (Fig. 2, Table 2). At Wooster, we assess bud injury as a % of 100 buds (10-bud canes). This is performed by variety.


Figure 2. Assessing bud mortality by cross-sectioning buds using a sharp razor blade. Notice the alive (left) vs. dead (right) status of the primary buds in the figure above.  

Table 2: Adjusted pruning based on % bud mortality.

% Primary bud injury


0 to 14%

No adjustment needed

15 to 34%

Retain an extra 35% buds

35 to 50%

Retain an extra 50% buds


Minimal prune to 5-bud spurs

80 to 100%

Likely trunk damage, renew trunk by retraining suckers


Why minimal prune? Yes, it’s a pain to shoot thin, but what we have noticed is that hedge pruning can aid in maintaining yield levels despite extensive (70-80%) primary bud injury. We have observed in the past that the rates of bud injury tend to be higher on node positions in the middle and end of canes vs. towards the base of canes. This means that buds retained from minimal hedge-styled pruning tend to be more alive than leaving more buds through cane pruning modifications (e.g., double-wrapping canes, quad-cane pruning).

Wood quality. Healthy, sun-exposed, reddish-brown wood that is approximately ¼ to ½” in diameter is optimal (think: Sharpie™, Pencil, Pen; Figure 3). This wood will contain buds with better cold hardiness, higher fruitfulness, and have the carbohydrate availability to support the development of 2-3 shoots. AVOID: bull wood (large, vegetive wood > ½” in diameter) and weak (< ¼” diameter).

Figure 3. Healthy, optimal wood selection for spurs and trunk and cordon training

When to prune? We acknowledge that larger vineyards are time-constrained and likely begin pruning earlier in the winter. However, if possible, small vineyards should wait as long as possible into spring. This is to allow compensation in case of winter injury, but can also help stave off early bud break by suppressing the development of the most basal buds on the cane (explained in our 2019 OGEN article: Grapevine Dormant Pruning). If waiting is not possible, begin with the most cold hardy varieties first, then proceed to the most cold sensitive varieties last (note* If you’re growing cold hardy MN hybrids, prioritize the later breaking varieties like Frontenac to prune first and prune the most early bud break varieties prone to spring freeze like Marquette and La Crescent last).

Pruning should be completed by the beginning of bud swell. Although bud break timing depends on numerous factors, we typically see signs of bud swell in mid to late-April in Wooster (may be 2-3 weeks different in southern and northern parts of Ohio). If you are double or delayed pruning as a spring frost avoidance strategy, final pruning needs to be completed no later than 1” in apical shoot growth. This is to avoid potential yield losses associated with basal bud break delays.  

Posted In: Viticulture
Tags: pruning, 2023 season
Comments: 0

The Wine Production Guide from Todd Steiner in collaboration between OSU and OGIC is now available for purchase through OSU Extension.

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Learn More: Looking for more resources on grape production, visit The Ohio State University Department of Horticulture and Crop Science at; Buckeye Appellation at; or search for “grapes” at OSU Extension’s Ohioline at


Posted In: Enology
Tags: Wine Guide
Comments: 0

By: Imed Dami, HCS-OSU

On December 23-24, Ohio experienced the coldest temperatures of the year 2022. Temperature lows ranged between 3F and -13F (see map). Statewide, the lowest temperatures occurred in West central Ohio and ranged between -9 F and -13F. In central Ohio, minimum temperatures ranged between -5F and -10F. In southwest, temperature dropped to -7F to -12F. In southeast, 3F to -6F were recorded. In Northwest, temperatures ranged between -3F and -11F. Northeast (majority of vinifera grape acreage) experienced the mildest temperatures ranging between -2F and -6F. At our research vineyard in Wooster, we recorded -7F on December 23, 2022.

To have a preliminary assessment of cold injury, we collected canes from our most cold sensitive vinifera varieties. We also collected a cold hardy hybrid, Frontenac blanc for comparison. Our findings were disappointing with higher-than-expected cold damage across the board. Table 1 summarizes cold injury of primary and secondary buds from 8 varieties. In vinifera primary bud injury ranged between 87% and 100%. Frontenac blanc sustained only 5% primary bud injury. Our results suggest that cold damage of vinifera varieties could be more severe than expected across the state. Hybrids (with LT50 of -13F or lower) should have minimum to no injury from this cold event. 

The extensive cold damage of vinifera varieties is puzzling. In late November, buds showed a good level of cold hardiness. For example, Chardonnay had LT50 = -7.7F. In December, low temperature of -7F was recorded in that vineyard in Wooster. So, at that temperature, we should have 50% or more bud survival. But, that was not the case and we had 10% primary bud survival (see Table 1). One way to explain this discrepancy is that vines lost cold hardiness in December. This is possible since we had a mild December with mean temperature 3F above the 30-year average (Figure 2).  

We still have a few weeks to go with winter weather and potential damaging temperatures are still possible.  Growers should be mindful of that and bud assessment, before pruning, is recommended. Pruning adjustment is definitely needed this year.  

Figure 1. Minimum temperatures on December 23-24, 2022. Note that minimum temperatures ranged between 3F and -13F. Source: Dr. Aaron Wilson, OSU state climatologist.

Table 1. Bud injury of 8 grape varieties exposed to -7F on December 23, 2022. Wooster, OH.




Primary bud injury (%)

Secondary bud injury (%)

V. vinifera


FPS 01




Cabernet franc

FPS 11





FPS 37





FPS 02





FPS 03




Sauvignon blanc

FPS 27









Frontenac blanc









Figure 2. Monthly mean temperature deviation from the 30-year average in 2022 in Wooster.  Bars above 0F means temperature was above the 30-year average. Bars below 0F means temperature was below the 30-year average.



Posted In: Viticulture
Tags: Viticulture, 2022 Season, Winter Injury
Comments: 0

By: Imed Dami and Diane Kinney, HCS-OSU

This article summarizes the 2022 dormant and growing seasons and the impact of weather on grape varieties grown on the research vineyard at the OSU-OARDC in Wooster, Ohio. 

Weather:  Temperature

The Wooster weather through the month of November has been nearly identical as 2021 with the averages being within 2 degrees each month. Once again, our winter low was within the tolerance level for all of our grape varieties, which had achieved maximum cold hardiness despite the fact we had a mild December when our lowest recorded temperature of -4.4 o F occurred on January 22nd.  Although our average temperatures for March and April were on track, we had a wide swing hitting 70+  oF a couple of days in early March,  as well as lows of 11 oF later in the month.  These low temperatures held off bud break due to low GDD’s.  The last week of April the temperatures finally warmed and induced bud break. Although many areas of the state were hit hard by a spring frost, in Wooster, damaging temperatures were avoided due to limited or no bud break of most varieties. The early ripening period during August and September remained largely on pace with not only 2021 but our 30 year-long term average while temperature dropped in October averaging 51 oF in comparison to 60 oF in 2021.  Our first hard freeze occurred on November 17th resulting in a growing season length of 201 frost-free-days.

Weather:  GDD 

We were very slow to gain GDD’s this year only hitting 100 in the later part of April but May roared ahead gaining over 300 GDD’s during the month putting us ahead of both 2021 and the long-term average.  We then settled down into normal gains until October were things just abruptly stopped, including fruit ripening.  Cumulatively, that averages out overtime, but we were well below our 2021 number of 3283 vs 3104 (thru November) in 2022.

Weather:  Precipitation

2021 ended the year with a total cumulative rainfall of only 30.99”.  We exceeded that amount in August of 2022.  By the end of November, we have recorded 39.62” which is 10” over the long-term average.  This is a change over the past 4 years where rainfall declined each year over the long term. 2022 has been very wet keeping us above the long-term averages every month up until October.   

Vineyard Notes:

2022 Spring freeze injury:  In Wooster we were fortunate to avoid a spring freeze event which wreaked havoc on a majority of the state the end of April.   We would have likely faired a bit better as our buds were in early developmental stages at this point versus southern regions of the state.

Diseases and insects:  Regular cover sprays were a must as we had consistent rains which resulted in sour rot.  Other diseases such as botrytis, downy mildew were seen in smaller amounts which caused minimal damage in our vineyard.  Our typical bird and other wildlife pressure was low while yellow jackets caused a fair amount of damage thereby helping encourage the spread of sour rot.

Fruit quality:   Sour rot caused a real challenge in fruit quality.  Our first harvest occurred on August 17th for Brianna and our final harvest occurred on October 25th for Chambourcin. Overall, fruit maturity was not as ideal as in 2021. In 2022, we recorded lower pH and higher TA as compared to 2021.

Table: 2022 Harvest fruit composition of selected grape varieties at the Wooster research vineyard:


Harvest Date

100 Berry wt (g)

SS (%)


T.A. (g/L)









Cabernet franc





















Crimson Pearl





















Frontenac blanc














La Crescent




























Sauvignon blanc 27














Posted In: Viticulture
Tags: vineyard updates, Viticulture, 2022 Season
Comments: 0

By: Doug Jackson-Smith, SENR OSU

The Ohio Grape Industries Committee (OGIC) recently asked researchers at the Ohio State University (OSU) to carry out a full census survey of growers who grew grapes in Ohio in 2021.  This report was designed to capture the acres and estimated production of various grape varieties in Ohio, and updates a report last issued by the USDA in 2017. The survey was completed by 148 farms (an 83% response rate), and documents 112 varieties raised on 1,222 acres across 55 counties (including 95 acres of newly planted vines). The results are interesting and can help grape growers and processors plan for the future. To see a copy of the full report in PDF – click here. A copy of this report and the technical appendix will be hosted under the Grape Growers tab of the Buckeye Appellation website. Questions regarding the survey and results can be directed towards Doug Jackson-Smith at


Posted In: Viticulture
Tags: Grape Census, Viticulture, Surveys, 2021 Season
Comments: 0