Recent Blog Posts
By: Maria Smith, HCS-OSU
My favorite week of the year is here: peak fall color has finally arrived in Wooster.
Like the maples, oaks, and hickories, grapevines are perennial woody plants that drop their leaves in the fall in a process called leaf senescence. This process is principally a response to hormonal cues (abscisic acid (ABA) and ethylene) and metabolism changes induced by shorter daylength and exposure to colder temperatures (32-50 F). However, several other factors influence the timing for leaf senescence, including stress factors (drought, disease), rootstock selection, and cropping decisions [1-4].
Leaf senescence plays a vital role in vine health through the reabsorption of nutrients that are stored overwinter and are used to support vine growth early in the growing season [5]. So, having an extended fall acclimation period has been nice in terms of seeing leaf yellowing in the post-harvest period prior to the first hard killing freeze (< 28 F) forecast for early next week. Typically, the first killing freeze on average in Wooster occurs during the last week of October, hastening leaf fall and dormancy.
During this time, there are still plenty of post-harvest activities still ongoing in the vineyard, including soil hilling for graft union protection, taking down netting and clips, and managing undervine weeds. As part of these activities, we encourage you to look at the vine foliage for deviations and patterns in leaf color.
In general, healthy grapevine foliage turns yellow in the fall (Fig. 1). This color is due to the breakdown of cell structures like chlorophyll that are in part responsible for reflection of green light. Some cultivars do characteristically have red leaves, therefore this is not universally true and why it’s important to know your cultivar traits (Fig. 2). However, conspicuous presence of red leaves in an otherwise sea of green and yellow, should elicit an eyebrow raise and further consideration for the overall vine health (Fig. 3), since red leaf coloration is related to stress response of the vine [6].
Figure 1. Typical leaf yellowing during grapvine acclimation in the post-harvest period at Hort Unit 2. Photo: Fernanda Cohoon.
Figure 2. Naturally occurring red leaf coloring in a Vitis hybrid. August 2025 NE Italy. Photo: Maria Smith
The University of Maryland and Rutgers University have both put together great resources regarding four different reasons leaves may turn red, identification, and management:
1) Nutrition deficiencies (potassium, magnesium)
2) Virus infection (Grapevine leafroll associated virus, Red blotch virus) -- Fig. 3
3) Crown Gall infection (Agrobacterium) -- Fig. 4
4) Canker and other trunk diseases (Eutypa, Botrysphaeria)
Figure 3. Red leaf coloration with green veins and leaf margin curling associated Grapevine Leafroll Associated Virus. Photo: Maria Smith
Figure 4. Red leaf coloration associated with Crown Gall infection (top) and gall formation on base of trunk that is leading to red leaf symptoms on only the right side of the vine (bottom). Photo: Maria Smith
Now that we’re moving into post-harvest, it’s time to take stock of the reason(s) you may be seeing red:
- Did your vine trunks experience winter injury that led to trunk infection (Crown gall, cankers)?
- Did excessively wet (spring) or dry (summer/fall) conditions limit nutrient availability and uptake (potassium, magnesium)? This may be more noticeable in young vines with limited root system establishment
- Have you been noticing year-over-year declines in yield and fruit quality, particularly among older Vinifera plantings (leafroll virus) that are otherwise healthy? (Fig. 5)
Figure 5. Cluster architecture of leafroll infected Cabernet sauvignon vines (top) vs. cluster architecture of asymptomatic Cabernet sauvignon vines (bottom). Photos: Maria Smith and Diane Kinney
The reasons inform the response. It’s important to observe patterns of leaf coloration throughout the growing season (emergence date, leaf age, distribution changes in the canopy) and, where feasible, keep close records of yield, fruit maturity, send tissue samples for diagnostics, regularly monitor vine nutritional status, and possible injury events to make informed determinations.
Citations:
[1] Poni et al. 1994. DOI: 10.5344/ajev.1994.45.2.252
[2] Peterson and Walker. 2017. DOI: 10.5344/catalyst.2017.16006
[3] Keller et al. 2014. DOI: 10.5344/ajev.2014.14042
[4] Edson et al. 1993. AJEV. 44:2. 139-147.
[5] Schreiner. 2016. DOI: 10.5344/ajev.2016.16019
[6] Espinoza et al. 2007. DOI: 10.1093/jxb/erm165
Erdal Ozkan. Professor and Extension State Specialist
The Ohio State University, FABE
Time to give your sprayer some TLC by properly winterizing it.
You probably won't use your sprayer again until next spring. To avoid potential problems, frustration, and major headaches next year, it's wise to give your sprayer some TLC (Tender Loving Care) this time of year. While there may still be other important matters demanding your attention, don’t forget to winterize your sprayer. Don't delay if you haven't done so already. You want to prevent a cracked pump or reduced efficiency caused by not properly winterizing before temperatures drop below freezing. Here are some essential steps to take with your sprayer now.
Rinsing
You probably did the right thing when you last used the sprayer: thoroughly rinsed the entire system (tank, hoses, filters, nozzles). If you didn't, be sure to do this before storing the sprayer. An unrinsed sprayer after each use, especially after the spraying season ends, can lead to cross-contamination of products applied to different crops next spring. Pay special attention to avoiding cross-contamination, which can cause severe crop damage, especially when using some of the newer 2,4-D and Dicamba herbicides. Another issue caused by not properly rinsing all sprayer parts is clogged nozzles. Once nozzles are clogged and remain that way for a long time, it becomes difficult to restore them to their normal working condition, which is what you expect from a properly cleaned nozzle. Leaving chemical residues in nozzles often causes changes in flow rate and spray pattern, resulting in uneven chemical distribution on the target.
The ease of properly rinsing a tank's interior depends on its type. It is very simple if the tank is relatively new and has special rinsing nozzles and mechanisms inside. If not, manual rinsing becomes more difficult and can pose safety risks, such as inhaling fumes from leftover chemicals during the process. To avoid these issues, you can either replace the tank with one that has interior rinse nozzles or install an interior rinse system in your current tank.
For effective rinsing of all sprayer parts, circulate clean water through the entire sprayer for several minutes first with the nozzles off, then flush out the rinsate through the nozzles. Rinsing should ideally be done in the field or on a concrete chemical mixing/loading pad with a sump to recover rinse water. In any case, dispose of the rinsate following the instructions on the pesticide labels you have used. Always check the label for specific directions. Most labels recommend the following procedure: if rinsing on a concrete rinse pad with a sump, return the collected rinsate to the tank, dilute it with water, and spray it in the field where it cannot reach ditches or other water bodies. If rinsing is done in the field, make sure you are not flushing rinsate in one area. It’s best to dilute the rinse water in the tank further and spray it on the field in places where it won’t contaminate nearby water bodies or ditches.
Cleaning
Rinsing the system with water, as explained earlier, may not completely remove chemicals from the sprayer. This could lead to cross-contamination issues. Residues of certain pesticides left in the sprayer might cause serious problems when applying a spray mixture containing those residues to a crop highly sensitive to that pesticide. To prevent such issues, it's best to thoroughly clean and rinse the entire spraying system with a cleaning solution. Usually, a mixture of 1 part household ammonia to 100 parts water works well for cleaning the tank. However, if the tank hasn't been cleaned for weeks or immediately after the last spraying, you might need to start with a detergent solution. Some chemicals require specific rinsing solutions. Always check the product label for the latest cleaning instructions.
Cleaning the outside of sprayer components deserves equal attention. Remove compacted deposits with a bristle brush. Then flush the exterior parts of the equipment with water. A high-pressure washer can be used if available. Wash the exterior of the equipment either in the field, away from ditches and nearby water sources, or on a specially constructed concrete rinse pad with a sump. Again, the rinsate should be disposed of according to the label recommendations. As I mentioned earlier, most labels recommend the same practice: put the rinsate collected in the sump back into the tank, dilute it with water, and spray it in the field where there is no potential for the rinsate to reach ditches or other nearby water bodies.
Winterizing
Recheck to ensure no liquid remains inside any of the sprayer parts to prevent freezing. The pump, as the core of a sprayer, needs special attention. You don’t want a cracked pump or one that isn’t working properly due to inadequate winterization before temperatures drop below freezing. After draining the water, add a small amount of oil, then turn the pump four or five revolutions by hand to coat the inside. Ensure this oil won’t harm rubber rollers in a roller pump or rubber parts in a diaphragm pump. Refer to the operator's manual. If oil isn't recommended, pouring one tablespoon of radiator rust inhibitor into the pump's inlet and outlet can also help prevent corrosion. Alternatively, use automotive antifreeze with rust inhibitor in the pump and other sprayer parts. This helps protect against corrosion and freezing if any water remains. To prevent corrosion, remove nozzle tips and strainers, dry them thoroughly, and store them somewhere dry. Another option is to submerge them in a can of light oil, such as diesel fuel or kerosene.
Storage
Find ways to protect your sprayer from the harmful effects of snow, rain, sun, and strong winds. Moisture in the air, whether from snow, rain, or soil, causes rust on the metal parts of all types of unprotected equipment. This is especially true for a sprayer, which has various hoses, rubber gaskets, and plastic components. While the sun can help reduce moisture in the air, it can also cause damage. Ultraviolet light weakens and softens rubber parts like hoses and tires, and degrades some tank materials. The best way to protect your sprayer is to store it in a dry building. Keeping sprayers inside also allows you to work on them anytime during the off-season, regardless of the weather. If storing inside isn't possible, cover the sprayer with a material that shields it from sun, rain, and snow. For trailer-style sprayers, place blocks under the frame or axle and reduce tire pressure during storage.
Finally, double-check all sprayer parts before leaving it behind. Identify parts that may need repairs or replacement. Inspect the tank and hoses for any signs of cracks or damage. Check the painted surfaces for scratches and touch up with paint to prevent corrosion. Also, remember to cover openings to prevent birds from nesting in the sprayer and to keep insects, dirt, and other debris out of the system.
By: Maria Smith, HCS-OSU
An abrupt change in weather patterns in late-July has changed the outcome for this growing season for fruit quality and maturity… but not before making its impacts on yield.
August/September weather
Precipitation
Genuinely, a tale of two very different halves to the season. What started out as unending rain has transitioned into mild to moderate drought conditions through mid-September (Fig. 1). From 1 Aug to 15 Sep, Hort 2 in Wooster has only seen 1.03” of cumulative rainfall, more than half of which fell in a single day (0.66” on 19 Aug). That is in contrast to the approximately 7.45” of cumulative precipitation typical of August and September long-term (30-year) cumulative precipitation (https://newa.cornell.edu/ and https://mrcc.purdue.edu).
This pattern is effectively due to a reverse of the same “Omega Block” pattern that lent itself towards our cool and very rainy spring. When will it change? I’m unsure. The 10-day outlook continues forecasting dry, warm, and sunny weather. I will discuss more on the implications for ongoing harvests and fruit quality below.
Figure 1. Current drought map for Ohio, as of 9 September 2025. Figure from https://droughtmonitor.unl.edu/.
Temperature and GDD
August average temperatures were on-the-mark this year at 70.1F (30-year average at 70.5F). So far, we are on track for near to above average (63.6F) September temperatures at 64.1F. However, it’s been a bit of a wild ride so far, with a 5-day stretch averaging 60.4F. For the grapes, a late-September warm-up to summertime temperatures bodes well for reaching better maturity across the back-half of harvest.
Growing degree days (GDD, base 50F) from 1 Jan to 15 Sep is currently 2574. The long-term, 30-year average cumulative GDD for 15 Sep is 2745, indicating an overall cooler year in Wooster. Interestingly, we are behind in temperature accumulation compared to the Kingsville vineyard (AARS), which is uncharacteristically ahead of Wooster and above average in heat accumulation for this year (currently 2738 vs 2524 for the 30-year average).
Fruit set, yield, and fruit maturity trends
The bloom period this year was marked by very cool and rainy conditions, leading to poor fruit set (Fig. 2) in several cultivars at Unit 2 in Wooster. The general trend for overall yields is lower this year, however, it’s unknown if this is purely due to poor fruit set or if there were carry-over effects stemming from the 2024 herbicide drift injury.
Figure 2. Poor fruit set and small cluster sizes in Regent at 100% veraison on 11 August 2025 (Top). Fruit set and cluster size was highly variable across several Vinifera and hybrid cultivars, including table grape Vanessa (Bottom).
With good diurnal temperature flucuations and dry conditions, overall fruit quality is high so far with only a few notable pre-harvest issues. This year, sugar accumulation is high, although with the cool September days, acid has been slower to degrade and is stubbornly high in the early- to mid-season cultivars (Fig. 3, for all reported cultivars, visit the 2025 Weekly Fruit Maturity Report at https://go.osu.edu/grapes). The warmer forecast should aid in reducing acidity moving over the next couple of weeks.
Figure 3. Weekly total soluble solid accumulation (top) and titratable acidity (bottom) for Regent (harvested 9/3/25) and Marquette (harvested 9/10/25).
Sure, we have some minor issues here and there, such as minimal foliar downy mildew in August (remember, it did rain at least a few days) and the occasional Phomopsis infection from the early season (Fig. 4). The real frustration for us this fall, because there’s always at least one, is the birds. Despite netting ahead of veraison this year, birds have been a persistent problem for continuing to hang fruit. Have you noticed that the grapes are there one day and gone without a trace the next, but there’s still a rachis? That’s likely bird damage (Fig. 5).
Several growers across Ohio have reported significant bird injury this year. If you are starting to see significant yield loss (>20%) as a result of bird damage, it’s better to harvest pre-maturely than to risk losing an entire crop.
UNH has one of the most extensive factsheets on managing birds in fruit crops. While netting is the most tried and reliable protection method, mesh size, shape, and timing of application are important variables to consider. In some cases, deploying multiple tactics may be necessary depending on the level of pressure and species causing damage. Some of the more common netting supplements and alternatives that I have come across over the past few years include Bird Gard auditory devices, laser deterrent systems, and raptor nesting for increasing natural predators. Adopting any practice comes with pros, cons, costs, and benefits. It is important to weigh these prior to adopting new protection methods for your operation.
Figure 4. Phomopsis infection in the rachis and berry in Vanessa at harvest (21 Aug).
Figure 5. Bird damage to Vanessa (top, 21 Aug) and Regent (bottom, 9 Sep) at harvest.
By: Maria Smith, OSU-HCS
A one-word summary of July: rain.
June/July weather
Precipitation
It has continued raining seemingly non-stop since the growing season kicked off in earnest in May. Contiguous with May, June saw 5.26” of cumulative precipitation at Hort 2 (https://newa.cornell.edu), nearly 0.9” above the 30-year long-term average. To date, Wooster has received 1.21” of precipitation in July. Although July was below the monthly long-term average (4.12”), the frequency of daily rainfall has been high, with measurable rainfall on 13/23 days (57%) so far. The forecast, however, is finally looking sunnier, and just in time for the pre-harvest period.
Temperature and GDD
We continue tracking similar to the long-term historic average for growing degree day (GDD). We are currently at 1646 GDD (base 50F, Jan 1) as of July 22, versus the long-term average of 1647 GDD. Following a cool May, June heat picked up the slack and bolstered GDD accumulation. The average daily temperature for June 2025 was 3.7F above the historical average, and thus far, July has been a whopping 7F above the historical average.
Phenology and Cultural Management
Of course, Heat + Moisture = Extra-planetary levels of vegetative growth.
And once the heat picked up in June, so did the amount of work we’ve had to manage. Shoot positioning, combing, hedging, and leaf removal came on hard and fast. And with the amount of vegetative regrowth, it seems to be a trend that will carry on through the remainder of the growing season (Figure 1).
Figure 1. Vegetative shoot tip regrowth (left) and recent hedging (right)
At the time of writing this post on July 22, we were at lag phase in berry development, the brief pause before the onset of veraison and have been performing crop estimation to determine final yield potential for harvest. Verasion began kicking off in our early varieties the last week of July, and we are currently beginning to enter veriaion in mid- to late-ripening cultivars. At Hort 2 in Wooster, we are anticipating harvest to begin around the last week of August in our earliest cultivars, though several southern Ohio vineyards have already reported full veraison in early cultivars, which would indicate harvest time beginning as early as next week (the first week of August).
Notable vine issues for harvest 2025
Fruit set in some cultivars was notably poor this year (Figure 2). Weather conditions during bloom heavily influence fruit set and yield potential. This year, bloom stretched nearly 2 weeks, during which the Wooster vineyard experienced cool temperatures and high rainfall.
Figure 2. Poor fruit set in V. vinifera Verdelho
In 2024, the Wooster vineyard was hit with 2,4-D herbicide injury prior to bloom, which significantly reduced yields in what was otherwise a very nice growing season. This year, vineyards with reported herbicide injury were impacted much later than in 2024, which allowed most vines to proceed through bloom with less crop loss. However, foliar injury may still limit the ability for full crop maturation.
Early season disease pressure was very high, particularly for Phomopsis, Anthracnose, and Downy mildew (Figure 3). At this point in the season, our attention turns to foliar downy mildew and bunch rot (Botrytis, Sour Rot, Ripe Rot) concerns. Veraison is one of the final opportunities for systemic fungicide use to manage some of these issues due to pre-harvest intervals and concerns regarding fungicide inhibition of fermentation.
Figure 3. Late-June foliar downy mildew (top) and fruit infection (bottom) in Vitis hybrid Marquette
Lastly, veraison is when bird deterrents and netting exclusions need to start being applied. The goal is to proactively restrict birds from receiving that first taste of grape that keeps them returning throughout the harvest period (Figure 4).
Figure 4. Over-the-row netting applied at the onset of veraison to high-wire cordon (HWC) hybrid block at Hort Unit 2.
By: Erdal Ozkan, Professor and Extension State Specialist, Department of Food, Agricultural and Biological Engineering-OSU
In contrast to field crops, vineyards and orchards exhibit significant canopy size and structural diversity. Interplanting vines of various ages within the same vineyard is a common practice that creates gaps between them. Additionally, canopy density can range from no canopy at all to a very dense canopy throughout the growing season, as shown below in pictures of the same vineyard in early season (left), mid-season (middle), and late season (right).
Unfortunately, with today’s conventional fixed-rate sprayers, the sprayer operator cannot turn nozzles on or off when there are gaps between grapevines. Similarly, operators lack the ability to deactivate some nozzles on the go when vine sizes vary from fully grown tall ones to short, small vines planted only a year ago. Under these conditions, much of the sprayed material is wasted, particularly during early-season spraying when there is minimal canopy cover. As a result, excessive pesticide use raises production costs and increases the potential for environmental contamination. An air-assisted, “intelligent sprayer” was developed in Ohio for variable-rate pesticide application in orchards, vineyards, and nurseries to tackle these issues. It detects canopy presence, measures size, shape, and foliage density, and then independently adjusts the spray output of individual nozzles to match canopy volume and travel speed in real-time. Field tests showed that this sprayer technology could reduce airborne spray drift by up to 87% (depending on the growth stage of the canopy and leaf density), decrease ground spray loss by 68–93%, and lower spray volume by 47–73% while maintaining effective control of insects and diseases. The “Smart Guided Systems” company has commercialized this technology in the U.S. The company offers components to retrofit existing constant-rate conventional “airblast” sprayers used in vineyards and orchards, enabling them to apply pesticides at a variable rate. This allows growers to modify their existing equipment and convert their constant-rate sprayer into a variable-rate sprayer at a fraction of the cost of a new sprayer.
Another recent technological development is the use of drones for spraying pesticides in vineyards. Drones are becoming increasingly popular, especially in areas where using conventional spraying equipment is neither safe nor practical. Currently, several factors—such as rapid advancements in drone technology, insufficient data on the effectiveness of drone applications compared to traditional ground sprayers, and Federal Aviation Administration (FAA) restrictions on drone operations—are hindering the adoption of drone spraying among fruit growers. However, given the substantial interest in and popularity of drone spraying, these limitations will likely be eased and addressed in the future. I will feature an article on the use of spray drones in an upcoming issue of this newsletter.
Detailed information on recent advancements in technology for effective spraying in orchards and vineyards is provided in the Ohio State University Extension publication (FABE-538) “Advancements in Technology for Effective Spraying in Orchards and Vineyards” (https://ohioline.osu.edu/factsheet/fabe-538).
Both the intelligent sprayer for variable-rate application and the spray drone will be demonstrated in a workshop on August 12, 2025. In addition to these new technologies, best practices for spraying with conventional vineyard sprayers will be discussed and demonstrated at this event. Additional information about this workshop, including registration details, can be found at this website https://ohiograpeweb.cfaes.ohio-state.edu/events/new-sprayer-technologies-and-best-spraying-practices-workshop.
By: Maria Smith, HCS-OSU
May weather:
Precipitation is the story so far.
Rain is an expected feature of spring in Ohio, and that’s not much of a debate. In fact, the 30-year average cumulative precipitation for May in Wooster is 3.73”. This year, we’ve received nearly 1” above that average with 4.59” of total cumulative precipitation (https://newa.cornell.edu Wooster Hort 2 station). The real uncanny part to me is the number of days that it has rained this month: 22 of 31 days. That’s right, we logged measurable precipitation for 71% the month.
…and the fun hasn’t stopped. June to date has logged an additional 2.18” across 4 total days of rainfall so far, which is nearly 57.6% of the 30-year average monthly rainfall, with more forecast over the next 7 days.
Temperature and Growing Degree Days (GDD)
Not only was May rainy, but it was also cool. The average daily temperature in May was 57.6 F, which is 2.6 F cooler than the 30-year average. Despite below average temperatures, cumulative annual GDD (720, base 50 F, January 1 to June 12) remains similar to, albeit slightly below, the 30-year average (787).
Phenology
Reports across the state place phenology anywhere from pea-size (Southeast Ohio) to pre-bloom and early bloom (Northeast Ohio).
In Wooster, we are moving through bloom this week, with some early hybrid cultivars (e.g., Itasca) near fruit set, while others (e.g., Cab Franc) are just beginning bloom (Figure 1, Table 1).
Figure 1. Clarion approaching post-bloom (top) and Regent at trace-bloom (right). 10 June 2025.
Table 1. 50% bloom date and GDD for select cultivars at Hort 2, Wooster, OH.
|
Cultivar |
50% bloom date |
GDD |
|---|---|---|
|
Cabernet Franc |
12-Jun |
720 |
|
Chardonnay |
13-Jun |
-- |
|
Regent |
12-Jun |
720 |
|
Albariño |
12-Jun |
720 |
|
Aromella |
13-Jun |
-- |
|
Traminette |
10-Jun |
681 |
|
Chambourcin |
13-Jun |
-- |
|
Marquette |
9-Jun |
674 |
|
Itasca |
5-Jun |
613 |
|
Petite Pearl |
9-Jun |
674 |
|
Clarion |
9-Jun |
674 |
|
Jupiter |
9-Jun |
674 |
Canopy management
With the rain and recent warming temperatures, shoots have reached nearly 3’ in length (Figure 2). Shoot and wire positioning Vinifera for VSP and suckering/thinning have been ongoing over the past several weeks. We are waiting to comb the high-wire shoots on the hybrids until the fruit starts to weigh the shoots down and shoot tips become less prone to breaking (Figure 3).
Figure 2. Regent canopy, VSP, 10 June 2025
Figure 3. Clarion canopy, High-wire cordon, 10 June 2025.
Disease updates
Cool, rainy conditions in May meant Phomopsis in several cultivars at Unit 2 (Figure 4). In more southern regions, many are also seeing Anthracnose stem and leaf infections (Figure 5). Reminder: we are still well-within the critical window for flower and fruit protection for all major diseases. This period over the next several weeks are the most important time of the season to ensure broad spectrum coverage using your best fungicides for preventative protection. For fungicides registered for grapes and disease efficacy, see: Midwest Fruit Pest Management Guide.
Figure 4. Phomopsis on shoots and leaves, Clarion, 27 May 2025
Figure 5. Anthracnose on Vidal blanc. Note how the lesions are gray in the center and sunken compared with Phomopsis. Leaf lesions of Anthracnose also fall out as the leaf tissue dies, leading to a “shot hole” appearance. June 2025. (Photo used with grower permission)
Insect management
It is right about time to start turning our attention to Grape Berry Moth (GBM). This is one of the handful of insects that can cause direct crop loss from fruit damage (Figure 6).
The other major insect to begin to start monitoring for is Japanese beetles. These foliage feeders can get out of hand quickly if allowed to accumulate large populations.
Some minor pests to monitor for include gall makers (grape cane gallmaker, grape tumid gallmaker), flea beetle larvae, and leafhoppers.
Scouting and monitoring (using GDD-based tools and traps) are the best means for deciding when insect control is warranted. In Wooster, we typically use fewer than 5 insecticide applications all season (this includes pre-harvest sour rot management sprays) by regular monitoring and providing well-timed and appropriate insecticide applications. Excessive use of insectcides may cause secondary pest infestations, including mites and mealybugs.
Figure 6. Berry damage from GBM in July 2024 (and some more Phomopsis on the stem).
Figure 7. Japanese beetle adult (top). Foliar feeding damage from Japanese beetles (bottom). July 2023.
By: Maria Smith, HCS-OSU
A few weeks ago (April 22), we officially hit the starting line of the 2025 growing season. Despite some late pruning in our cold-hardy hybrid block, we are now finally at greater than 50% bud break in all cultivars at Hort Unit 2 in Wooster (Table 1).
The good news is that this is one of the most “normal” starts to the growing season that we’ve had in years. Despite the polar vortex events of late January, bud injury was limited to less than 10-15% in most cultivars, including cold-sensitive Vinifera, and we narrowly avoided widespread freeze on 27 April, even if some vineyards had frost formation. There is another frost advisory forecast for tomorrow morning (8 May) in Ashtabula County, however, actual temperatures are only expected to reach the low-40s to upper-30s F, so we should still be safe from widespread freeze.
Table 1. 50% bud break date of key trial cultivars at Hort Unit 2, Wooster, OH and GDD at bud break (base 50°F, 1 Jan to bud break date)
| Cultivar | 50% Bud break date | GDD (Base 50F) |
|---|---|---|
| Clarion | 4/22 | 209 |
| Frontenac blanc | 4/23 | 220 |
| Petite Pearl | 4/25 | 252 |
| Crimson Pearl | 4/25 | 252 |
| Itasca | 4/21 | 203 |
| Marquette | 4/23 | 220 |
| La Crescent | 4/23 | 220 |
| Aromella | 4/25 | 252 |
| Jupiter | 4/21 | 203 |
| Neptune | 4/28 | 269 |
| Cab Franc FPS 11 | 4/21 | 203 |
| Chardonnay FPS 37 | 4/23 | 220 |
| Albarino | 4/23 | 220 |
| Regent | 4/23 | 220 |
| San Marco | 4/28 | 269 |
Management considerations for the early season
Many growers have reached out over the past couple of weeks pertaining to management questions regarding cultural, pest, and weed management. The following information should help answer some of those questions.
Cultural management
Each growing season has a list of in-season canopy management tasks that should be completed in accordance with best grape growing practices. These include:
- Shoot thinning, trunk suckering (6-12” shoot growth)
- Leaf removal (fruit-set)
- Cluster thinning (pea-size to bunch closure, when appropriate)
- Shoot positioning (bunch closure to lag phase)
- Shoot hedging/skirting (shoot tips folding over the trellis top, shoots on the ground)
We’ve finally reached the point in several cultivars at Hort Unit 2 are ready to be thinned/suckered (Figure 1). Keep in mind the priorities of shoot density, spacing, fruitfulness, and positioning (conformation to the trellis system, trunk/cordon replacement, and proximity to the fruiting wire). Even in cane-pruned vineyards, vines may require some, albeit minimal, shoot thinning to remove secondary and tertiary shoot emergence.
For more information on shoot thinning, see: Best viticulture practices: Shoot thinning
Figure 1. (1) Shoot thinning (5/7/2025), (2) and (3) pre-thinning vs. post thinning spur position (NY 06), thinned cordon to 7 shoots per foot of cordon length (Frontenac blanc), (4) trunk suckering in Cabernet Franc (vertical shoot positioned) and thinned (left cordon) vs. unthinned cordon (right cordon)
Pest Management
Disease
With shoots rapidly growing and the weather producing so much rain over the past few weeks, Phomopsis has started to pop up in susceptible cultivars (Figure 2). For context, we have had measurable rainfall in Wooster every day since 1 May, with a cumulative precipitation of 2.56”, 3.66” since 22 April.
At the Hort 2 vineyard, we are shortening our spray intervals to every 7 days of Mancozeb and JMS Stylet oil (we have sulfur-sensitive cultivars planted) while we are stuck in what feels like an infinite loop of precipitation. To be more precise, I recently learned that it’s called an “Omega Block” and is the cause of this weather pattern. Once we reach the pre-bloom stage, we will begin to incorporate systemic fungicides into our spray program and will reconsider our intervals at that time.
To note, mancozeb has not had a final decision made regarding its registration status and can still be used for the 2025 growing season. We will provide an update on mancozeb guidance when it becomes available.
Because we’re rapidly approaching the critical period for disease management, I wanted to share some wisdom on practices for fungicide resistance management from Katie Gold’s article from the latest Finger Lakes Newsletter:
Fungicide resistance stewardship practices for commonly used products
- SDHI products (FRAC 7) such as the Luna family, Aprovia, Miravis Prime, Pristine, and Endura, no more than 3x/season and never twice in a row
- QOI products (FRAC 11) such as Abound, Azaka, Reason, Sovran, Topguard EQ, Flint Extra, Intuity, Pristine, and Quadris no more than 3x/season & never twice in a row– with caution, PM & DM resistance is well documented
- DMI products (FRAC 3) such as difenoconazole (the “Top” in common combos), Cevya, Inspire Super, Mettle, Rally, Procure, Rhyme, tebuconazole, and Topguard EQ no more than 3x/season & never twice in a row
- Revus and Zampro (FRAC 40) no more than 3x/season & never twice in a row – with caution, as resistance is well documented
- Vivando and Prolivo no more than 2x/season and never twice in a row
- Gatten, Torino, or Quintec no more than 2x/season each and never twice in a row
- Ridomil NEVER more than once per season
Figure 2. Phomopsis lesions developing on Clarion (MN1220) at Hort Unit 2, Wooster, OH. Photo taken May 6, 2025. Notice the small black lesions with a surrounding yellow halo.
Insects
For the most part, when growers have sent in images of perceived pests they have, for the most part, been benign or friends. There are, however, instances of pests to watch out for early in the growing season. These include rose chafers, cutworms, and flea beetles. These pests cause damage through feeding on young buds and shoots. Flea beetle larvae can also cause damage to foliage (Figure 3). The threshold for control is low for these insects because of their ability to significantly reduce vineyard productivity and yield, but scouting is paramount for insect signs and injury symptoms prior to using insecticides.
For those who have cultivars that are highly susceptible to foliar phylloxera (e.g., cold-hardy Riparia hybrids), control can be timed using growing degree days (GDD) or via incorporation of insecticides at key stages of vine growth. For more information on foliar phylloxera, visit Practical Tips for Managing Grape Phylloxera in Minnesota.
Since GDD coincides with insect lifecycles, we can use them in conjunction with vine growth stages as well. Key insecticide timings for managing grape foliar phylloxera are summed up from Dr. Ashley Leach’s 2024 Ohio Grape and Wine Conference presentation here:
- Danitol (restricted use):
- Application 1: Pre-bloom
- Application 2: 10-14 days later
- Movento:
- Application 1: 4-10” shoot growth
- Application 2: 30 days later
Figure 3. Flea beetle adult (left) and larvae (right) feeding on grape foliage
Weed management
With the vines having growth initiated, RoundUp (Glyphosate) is not recommended for use until later in the fall after the first killing frost. However, several contact options remain available for use during the growing season, including Rely 280, Aim, Gramoxone (restricted use), and Venue (original and Max formulations). These can also be tank-mixed with registered pre-emergent herbicides to provide residual control of weeds throughout the remainder of the season.
Similar to insects, scouting and identifying the weed population is a critical component to the success of an herbicide program.
With all pesticides, read the label before use. Some pre-emergent herbicides have restrictions with vine age and the yield-bearing status of the vines. For more information on vineyard herbicides, refer to the herbicide section of the Midwest Fruit Pest Management Guide.
Of course, there are non-chemical management options, as well. These include mechanical tillage, mowing, ground cover use, and integrated livestock (sheep! Figure 4). I will be reviewing options for alternative weed management in the coming months.
Figure 4. Sheep grazing the vineyard floor (January 2025)
Herbicide Drift
Yes, it is that time of year again, and yes, I do expect this to be a long-term, ongoing annual problem. I have been seeing yellowing weeds around Wooster lately, which means that fields are being prepped with herbicide use. It is important to keep very close watch for neighboring applications, onsite weather conditions, and any symptoms of herbicide drift injury over the next 6-8 weeks. Please see the OSU factsheet series on preparing for and responding to herbicide drift injury. Working cooperatively with neighboring applicators is the best solution to avoiding drift injury.
We encourage all grape growers who experience herbicide drift injury to report to ODA. I fully understand and empathize with frustrations and anxieties over both the issue and process. However, the only formal way to document and quantify incidences of drift injury in Ohio is to report it. Remember: anecdotes are not evidence.
Wishing all of us fair weather and a trouble-free, productive growing season.
By: Maria Smith, HCS-OSU
While we anticipate yet another round of arctic air here in Ohio this coming week, we are forecast to be well-above the temperatures we achieved just a few weeks ago (>0F) and not expecting compounding injury from January.
For context: On 22 January 2025, we experienced one of the colder polar vortex events of recent winters, which sent temperatures plunging between -2F and -13F statewide (Figure 1).
With temperatures that cold, some damage (particularly to cold-sensitive Vinifera) is expected. However, spoiler alert, it overall was not nearly as damaging as one might expect.
Figure 1. Minimum temperatures by county on 1/22/2025. Red indicates stations from MRCC (https://mrcc.purdue.edu) and blue indicate NEWA stations (https://newa.cornell.edu). Figure by Fernanda Cohoon.
Bud Injury – Wooster
The station minimum temperatures in the cultivar evaluation blocks of Hort Unit 2 reached -8F. Below is the extent of bud injury experienced among a range of Vinifera and hybrid cultivars (Table 1).
It is important to emphasize that site selection played a critical role in the localized minimum temperatures at Hort 2. Prevailing calm winds (< 2 mph) created radiative conditions, with cold air settling in topographic depressions and lower elevations areas within the site. Across the 45 acres of Hort 2, temperatures from 3 different weather stations ranged between -8F and -10F. The Vinifera grapes (BLK C) and cold hardy hybrid trial (BLK D) are planted on the highest elevation within the site with multi-directional air drainage that inhibits cold air from pooling within the planted grape block.
Why higher mortality among Clarion (MN1220) and NY 06? The higher percentage of bud injury in Clarion (MN 1220) and NY 06 may be related to the herbicide drift injury experienced in the BLK D variety trial vines during the 2024 growing season. BLK D had the highest observed herbicide injury among all 4 planted trial blocks at Hort 2. It’s unknown, however, whether bud mortality was directly caused from herbicide injury or if the observed mortality resulted from lower hardiness and cold injury since bud dissection was not performed until after the January cold event.
Table 1. Bud injury rates of select Vinifera and hybrid cultivars at Hort 2 (Wooster, OH). Data from Fernanda Cohoon and Diane Kinney.
|
Variety |
Overall Injury |
Prim. bud Injury |
Sec. bud Injury |
Tertiary bud Injury |
|
Chambourcin |
8% |
14% |
6% |
4% |
|
CF FPS 11 |
11% |
23% |
5% |
6% |
|
Primitivo |
62% |
87% |
62% |
35% |
|
Regent |
13% |
28% |
7% |
3% |
|
Crimson Pearl |
6% |
12% |
3% |
2% |
|
Frontenac blanc |
5% |
8% |
8% |
0% |
|
Clarion (MN 1220) |
20% |
27% |
18% |
15% |
|
NY 06 |
31% |
48% |
19% |
26% |
Bud Injury – Ashtabula
Cane samples for several standard and select cold-sensitive Vinifera varieties were collected for bud injury from AARS and commercial vineyards in Ashtabula County to assess damage over a representative range of regional conditions. Overall injury rates from Vinifera at the AARS Kingsville station and commercial vineyards from Grand River Valley (Geneva, OH) and Conneaut Creek (Conneaut, OH) ranged between 2% (AARS Pinot Noir) and 13% (AARS Sauvignon Blanc). Minimum temperatures at AARS reached -5.8F, but temperatures reported from Grand River Valley were reported to be as low as -10F.
Table 2: Overall bud injury (primary, secondary, and tertiary) among of select cultivars and sites within Ashtabula County. Data from Aaron Jaskiewicz, Patrick Turner, and Andy Kirk.
|
Site |
Kingsville |
Conneaut |
RT 307 |
RT 534 |
S. River Rd |
|
|
Variety |
||||||
|
Cab Franc |
10% |
5% |
7% |
|||
|
Cab Sauv |
3% |
|||||
|
Chardonnay |
5% |
11% |
9% |
7% |
||
|
Merlot |
5% |
|||||
|
Pinot Noir |
2% |
5% |
7% |
4% |
||
|
Sauv Blanc |
13% |
|||||
|
Saperavi |
6% |
8% |
||||
Aligning Wooster DTA information with the Bud Cold Hardiness Model Using Cabernet Franc
The cold hardiness model provided by the Londo lab at Cornell University estimated 50% bud injury for Cabernet Franc at Wooster at -16.78F (Figure 2). DTA (differential thermal analysis – a procedure to collect our own estimates of cold hardiness) from Unit 2 in mid-January estimated LT50 cold hardiness of Cab Franc FPS 11 at -16.55F, which was very close to the model-estimated -16.78F. While it’s possible that hardiness may have been over-predicted (Figure 3), Cab Franc and other Vinifera varieties were able to survive between -5 to -10F actual minimum temperatures without significant injury levels (>15%) in Northeast Ohio.
*Note: the Cornell Bud Cold Hardiness model has been integrated into the NEWA application. For an example of the output, see Figure 4. Only select cultivars are included with the NEWA model integration.
Figure 2. Predicted cold hardiness of Cabernet Franc using Wooster, OH weather station data. Model-predicted hardiness for Jan 23 was -16.78F and an actual minimum recorded temperature for this station was -9.76F.
Figure 3. Cabernet Franc cold hardiness data from the Geneva, NY research station that overlays DTA estimated cold hardiness with model-predicted values. LTXX lines indicate estimated temperatures at which 10 (-10.84F), 50 (-14.44F), and 90% (-18.22F) bud injury would occur. LT50 is approximately +2F less hardy than model-estimated values.
Figure 4. An example of the Grape Cold Hardiness Risk Assessment Tool using the Wooster Hort 2 weather station through NEWA.
Recommendations for bud adjustments to accommodate injury rates
We will discuss strategies for adjusted pruning and bud retention at the upcoming Wooster Pruning Workshop on Thursday, March 6.
The best course of action for managing winter cold injury is to 1) assess the amount of injury within your vineyard prior to dormant pruning using a representative sample of 100 buds (10 canes with 10 nodes per cane for each variety/vineyard block to dissect), and 2) adjust bud retention values to appropriately accommodate the amount of sustained injury for your site and varieties.
The additional number of buds to retain is relative to the percentage of damaged primary buds. The following table (Table 3) provides general guidance for how many additional buds to retain with respect to the percent of observed bud injury. Additional information on identifying bud injury and management can be found in the factsheet Assessing and Managing Winter-Damaged Grapevines Part II: Early Spring
Table 3. Recommended bud retention adjustments based on assessed primary bud injury.
|
Primary bud damage (%) |
Adjustment |
|
< 15% |
No adjustment needed |
|
15-34% |
Leave approximately 35% more buds |
|
35-50% |
Double number of buds |
|
51-75% |
Minimally prune vines (5-bud hedge) |
|
>75% |
Expect minimal yield, vascular damage and vine cordon/trunk replacement |
Thankfully, most damage this year thus far appears to be minimal. However, with Buckeye Chuck predicting an early spring, there is still opportunity for injury to occur moving into late winter. Though, to be fair to Chuck’s skills, he currently ranks 8th among all prognosticating groundhogs and is only right about 55% of the time.
By: Maria Smith and Diane Kinney, HCS-OSU
This article summarizes the 2024 dormant and growing season conditions and their impact on grape varieties grown at the research vineyard of the CFAES-Wooster Campus.
Weather: Temperature
2024 can be summarized as a warm, dry year. Aside from July and August, which were close to the 30 year long-term average, each month ranged between 1.3 to 6.4 °F above average monthly temperatures.
A 29 °F frost event was recorded on April 25th in Wooster, but we avoided any major damage to buds even though bud-break was completed throughout the vineyard. Damage estimates ranged from ~10% in hybrids to as much as 30% in select Vitis vinifera. Although mid-year temperatures returned near average, overall warmer temperatures accelerated harvest by 2 to 3 weeks ahead of typical expectations. From 1-Jan to 30-Nov 2024, temperature departures averaged +2.7 °F. Above-average fall temperatures lead to a very late killing frost on 29-Nov. This allowed vines to slowly acclimate due to a much longer period of frost free days (FFD = 218) in 2024 vs. 187 in 2023.
Figure 1. Temperature departure from 30-year long-term average for 1-Jan to 30-Nov 2024.
Weather: Growing Degree Days (GDD)
Accumulation of GDD units (base 50 °F) were consistently ahead of both 2023 and the long-term average from April onward. Greater than 3000 GDD were accumulated prior to the end of September, and, as of the end of November, we have recorded 3276 GDD. This has far surpassed 2023, which accumulated just 2231 GDD for the same time period of 1-Jan to 30-Nov.
2024 is on track to be the third warmest growing season in the last 10 years exceeded only by 2016 and 2021, which recorded 3365 and 3294 units respectively.
Figure 2. Monthly GDD from 1-Jan to 30-Nov for 2024, 2023, and the 30 year long-term average.
Figure 3. Cumulative GDD from 1-Jan to 30-Nov for 2024, 2023, and the 30-year long-term average.
Figure 4. Annual cumulative GDD from 2015-2024 compared with the 30-year long-term average GDD. 8 of the past 10 years have seen above average cumulative GDD. 2024 was the 3rd warmest year in the past 10 years.
Weather: Precipitation
2024 has been a very dry year overall, with drought conditions emerging during June and July. As of November 30th, we were more than 4” below the long-term average (32.7”), with a total accumulation of just 28.5”. Both June and October were nearly 2.5” below the long-term average, and October recorded only 0.34” total rainfall. This is the second year in a row Wooster has experienced a very dry year (2023 cumlative preciptiation = 29.4” during the same time period, 1-Jan to 30-Nov). Low rainfall in September and October overall benefited fruit quality and vine health through low disease pressure and ability to achieve higher fruit maturation values, especially for late-ripening varieties.
Figure 5. Monthly precipitation departures from 30-year long-term average.
Figure 6. Monthly cumulative precipitation for 2024, 2023, and the 30-year long-term average.
Figure 7. Monthly cumulative preciptation for 2024 and the 30-year long-term average.
Vineyard Notes
We avoided damaging winter freeze events this year due to very mild winter temperatures, with the lowest temperature reaching just +1.4 °F on 15 January 2024. The mild winter lead to earlier phenological development in the spring, with the onset of bud break occuring more than 1 week in advance of average dates. Despite forecasted threats, we had only one spring freeze event in late April that resulted in minor damage. Unfortunately, the most significant issue we encountered during the 2024 season was a 2-4, D drift event in early May. Both our hybrid and vinifera variety trial blocks were greatly affected, with most varieties showing irregular vegetative shoot development and poor fruit set. This significantly reduced our yield levels at harvest and was devastating considering the overall ideal growing conditions for what should have been a banner vintage. Our earliest ever harvest began with Brianna on 8-Aug and was completed on 23-Sep with Cabernet franc.
Diseases and insects: Due to the drier weather, diseases were less of an issue this season. Birds however, appeared early and hit hard in mid-July coinciding with early veraison. Yellow jackets made another appearance, but caused fewer problems than the birds. Netting issues exacerbated bird damage, which, combined with the spring drift, reduced our final yields even more.
Fruit quality: As with most years, sour rot continues to be one of our biggest challenges to fruit quality. This year, sour rot was relativley minimal due to the dry fall conditions. However, heavy bird pressure and wasp/yellow jacket/bee pressue did lead to rot conditions in some varieties. Dry, warm weather allowed us to ripen all of our fruit to desirable maturity. Berry weights reflect those varieties affected most by drift. Total soluble solids (TSS) and pH were overall higher than past years but acids also tended to be higher as well.
Figure 8. Herbicide drift injury symptoms in vegetation and fruit of MN1220 (Clarion), top and MN 1285 (Itasca), bottom. Photos from Diane Kinney.
Table 1. 2024 Harvest fruit composition of selected grape varieties at the Wooster research vineyard. (2022 data in parentheses).
|
2024(2022)
|
|
|
|
|
|
|
|---|---|---|---|---|---|---|
|
Variety |
Harvest Date |
100 Berry wt (g) |
SS (%) |
pH |
T.A. (g/L) |
FMI |
|
Brianna |
8 - Aug (17-Aug) |
268 (268) |
17.6 (17.1) |
3.15 (3.00) |
6.6 (8.1) |
27 (19) |
|
Cabernet franc |
23- Sep (11- Oct) |
157 (141) |
22.9 (20.9) |
3.23 (3.13) |
7.2 (8.1) |
32 (26) |
|
Chardonnay |
12 - Sep (27 Sep) |
175 (186) |
21.9 (21.2) |
3.31 (3.14) |
9.1 (8.5) |
24 (25) |
|
Clarion - MN 1220 |
28-Aug (27 Sept) |
165 (195) |
23.5 (22.3) |
3.03 (3.27) |
11.3 (8.0) |
21 (28) |
|
Crimson Pearl |
27 - Aug (21 - Sep) |
208 (206) |
20.6 (20.7) |
3.05 (3.35) |
8.6 (8.4) |
24 (25) |
|
Einset |
13 - Aug (31 Aug) |
273 (252) |
19.0 (19.3) |
3.11 (3.12) |
6.0 (5.4) |
32 (36) |
|
Frontenac blanc |
5 - Sep (21 Sep) |
127 (125) |
25.2 (23.7) |
3.19 (3.11) |
11.8 (14.7) |
21 (16) |
|
Itasca - MN 1285 |
22 - Aug (21 - Sep) |
126 (152) |
22.8 (22.9) |
3.19 (3.50) |
9.3 (8.6) |
25 (27) |
|
Jupiter |
14 - Aug (8 - Sep) |
432 (419) |
18.4 (18.2) |
3.11 (3.36) |
7.1 (5.5) |
26 (33) |
|
Marquis |
21 - Aug (9 - Sep) |
440 (502) |
15.5 (13.9) |
3.23 (2.88) |
5.3 (5.1) |
29 (27) |
|
Petite Pearl |
5 - Sep (21 - Sep) |
125 (120) |
22.3 (20.6) |
3.32 (3.24) |
7.6 (8.3) |
29 (25) |
|
Regent |
29 - Aug (15 - Sep) |
223 (251) |
20.1 (19.8) |
3.14 (3.07) |
8.1 (7.2) |
25 (28) |
|
Vanessa |
13 - Aug (1 - Sep) |
274 (274) |
18.8 (18.0) |
3.11 (3.21) |
5.3 (4.8) |
35 (37) |
|
Verona |
11 - Sep (22 - Sep) |
207 (213) |
19.8 (18.7) |
2.77 (2.95) |
9.5 (9.0) |
21 (21) |
They say history doesn’t repeat, rather it rhymes. And right now, it’s feeling much like January 2014-2015 over here:
- Jan. 7, 2014: The term “polar vortex” enters the public lexicon with extreme damaging cold temperatures. A similar historic event would repeat Feb. 20, 2015.
- Jan. 15, 2015: OSU defeats Oregon in the first 2014 CFP national title, 42-20.
Ten years later in 2025, OSU wins the first expanded CFP national title and this evening’s forecast tonight calls for lows throughout the state anywhere between 1F and -11F (Figure 1), with cold temperatures (< 0F) expected to persist from 8pm through 10am.
Figure 1. Forecast nighttime low temperatures Jan 22, 2025. Figure from https://weather.gov.
Some key differences from 2014-2015:
- Vine cold acclimation is much better than in 2014-2015. A late first fall freeze aided in improving winter hardiness through extending wood maturation, carbon and nutrient reassimilation.
- Sustained below-freezing temperatures through January (Figure 2) have aided in achieving maximum cold hardiness while minimizing deacclimation and freeze/thaw cycles, which often leads to more extensive bud/tissue injury.
Figure 2. Average temperature departure from long-term mean from 22 Dec 2014 through 20 Jan 2025. Figure from https://climate.osu.edu.
- Persistent snowpack provides an insulating layer that helps protect the base on the vine trunk.
- Our most recent estimates of LT50 (e.g., minimum temperatures that result in 50% bud injury) from cultivars at Unit 2 suggest many Vinifera cultivars have attained cold hardiness to approximately -10F and hybrids < -15F. These values are similar to reported LT50 estimates from Cornell University.
We will be following up in the coming week with temperature minimum descriptions, incidence of bud injury, and recommendations for adjusted pruning.
In the meantime, stay warm!