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By: Melanie L. Lewis Ivey, Associate Professor, Extension Fruit Pathologist, Department of Plant Pathology
This article can be found in the January 2024 issue of Ohio Fruit News.
In December 2023, the Environmental Protection Agency (EPA) proposed an interim decision for the registrations for thiram, ferbam and ziram. Despite updates and recommendations for ziram, presented during the public comment period for the 2021 proposed interim decision, changes were not made to the previous risk picture and proposal.
Thiram, ferbam and ziram are critical to the successful management of fruit diseases and the prevention of fungicide resistance development. Final decisions on the proposed interim decisions are scheduled for April-June 2024. An open 60-day public comment period is planned for the beginning of 2024. Once the comment period opens, comments can be submitted on-line or by mail. Open comment periods are announced at www.epa.gov/pesticide-reevaluation.
Representatives from the EPA have emphasized that without new data or significant numbers of comments, the proposed interim decision on these products is unlikely to change.
The EPA will only announce final changes to the registrations of all pesticides through the “Bulletins Live – 2” website. However, the OSU Extension Specialty Crop Team will make every effort to keep fruit producers in the state updated.
Figure 1. Peach leaf curl is most effectively controlled using Ferbam or Ziram. Image courtesy of K. Peter, Penn State University.
Thiram
Docket EPA-HQ-OPP-2015-0433
Risks of Concern: There are risks of concern for “fish (both freshwater and estuarine/marine), aquatic invertebrates, mammals, terrestrial invertebrates, birds, and aquatic and terrestrial plants.” In addition, there are “exposure concerns to occupational handlers and post application risks”.
Proposed Mitigation: To address the risks of concerns for thiram the following mitigation strategies were proposed.
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Cancellation of all non-seed treatment uses such as strawberries, peaches, non-bearing trees, shrubs, nursery stock, ornamentals.
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Cancellation for all commercial seed treatment uses.
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Only on-farm seed treatment for liquid formulations and use of a PF10 respirator for some crops (snap bean, rice, soybean, and wheat).
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Limit animal repellency use in nursery settings (ornamentals, vegetables, trees, container stock) to 84178-1 only. This product is also registered for other use sites and those uses must be removed from the label. Applications must be made with a manually pressurized handgun. All other products must remove their animal repellency use from the label.
Ferbam
EPA-HQ-OPP-2015-0567
Risks of Concern: There are risks of concern for “fish (both freshwater and estuarine/marine), aquatic invertebrates, mammals, terrestrial invertebrates, and birds.” In addition, there are “exposure concerns to occupational handlers and occupational post application risks for workers”.
Proposed Mitigation: To address the risks of concerns for ferbam the following mitigation strategies were proposed.
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Cancellation of all uses on apple, pear, citrus, mango, and cranberries.
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Restrict the application method to only be applied by a mechanically pressurized handgun on peach and nectarine for dry flowable formulations and require the use of a PF50 respirator.
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Only dormant period applications for peaches and nectarines.
Ziram
EPA-HQ-OPP_2015-0568
Risks of Concern: There are risks of concern for “fish (both freshwater and estuarine/marine), aquatic invertebrates, mammals, birds, and terrestrial invertebrates”. In addition, there are “dermal and inhalation exposures to occupational handlers, post-application occupational risks (dermal), and bystander (non-occupational) risks to adults (dermal) and children (combined dermal and incidental oral)”.
Proposed Mitigation: To address the risks of concerns for ziram the following mitigation strategies were proposed.
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Cancellation of all uses on all crops.
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Cancellation of uses for paint preservatives.
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Engineering controls for the non-paint materials preservative uses.
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Reducing the maximum application rate in all ziram-preserved building materials.
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Limiting application to the dry-end of the paper preservation process.
By Imed Dami and Diane Kinney, HCS-OSU
This article summarizes the 2023 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
Our 2023 growing season was greatly affected by a freeze event on December 23, 2022 to -7 F. Bud injury was higher than normal due to warmer (3F) than a typical December. The early part of the year was significantly warmer than both the long-term average and 2022 temps. This did not hold true for the early growing season though as temperatures were below in both areas. In Wooster, we missed a frost event in mid-May that greatly affected other grape growing regions in the state. Our last date for temperatures below freezing in the spring was April 27th which coincided with bud break. Phenological progress was slow due to cool, dry temperatures. During fruit ripening in early fall, temperatures followed closely to both long-term and 2022. Cumulatively, as year end, we are only slightly above 2022. We did have an earlier fall frost date of October 31st resulting in a lower-than-average FFD of just 187 in comparison to 201 in 2022.
Weather: GDD
Nearly 40 GDD units were gained during early winter from the 1st of January through 1st of April. April continued to be slightly above both 2022 and the long-term averages but things drastically dropped off for the entire growing season May through September. By years’ end, we are at only 2734 GDD vs 3104 in 2022 which was already significantly lower than 2021. In relation to the long-term 30-year average of 3058 GDD, we are 324 GDD lower at this time. This is the first time that yearly GDD dropped below 3000 in 10 years.
Weather: Precipitation
Annual precipitation was above the long-term average but significantly below 2022 (34.53” vs 41.03”). That being said, we did have near drought like conditions during the early growing season mid-May through mid-June with nearly no rainfall at all. This early drought ended with nearly 3” the last two weeks of June alone. July and September were also very dry. A 5-day period in early August recorded 2.69” with another near 3” the last week of the month. In September, we only recorded 0.32” with November at 1.36”. In general, and except August, we had a drier than normal summer-fall, which impacted disease pressure in 2023.
Vineyard Notes:
2023 Winter freeze injury: The deep freeze of December 23, 2023 caused significant bud injury. Vinifera varieties (15) sustained 85-100% primary bud injury; Table grapes (8): 55-100%; hybrids (19): 15-82%. The causal claims, that the temperature dropped very fast, are not accurate. In our vineyard, temperature dropped about 50F in 24 hrs or 2F/hr. That is considered a normal “freezing rate”. It is the mild December that led to “deacclimation” of vines. Also, the freeze-thaw cycle (45F/-7F) just before the event exacerbated the extent of damage. However, the crop loss in some varieties was not as severe as expected due to our pruning adjustment. For example, Chardonnay sustained 85% bud injury but produced 3 tons/acre after hedge (or minimal) pruning.
Diseases and insects: With the drier weather, diseases were also less of a problem this year. Bird and racoon damage was nearly non-existent, but yellow jacket damage was fair which led to high sour rot incidence. Dr. Ivey confirmed a new disease, called ripe rot, for the first time in Ohio that we found in some of the varieties in Wooster. More information regarding this will be shared at a later time.
Fruit quality: Sour rot continues to be our biggest challenge in fruit quality. Harvest began on August 23rd for Briana and our final harvest occurred on October 5th for Cabernet franc. Despite a very low GDD, we were able to ripen fruit of most varieties and fruit composition was appropriate. For example, in 2023, sugars in 14 varieties averaged 19.9 Brix. In 2022, the average was almost the same at 19.8 Brix. Acidity was also below 10g/L in general despite a cool season. TA averaged 7.5 g/L in 2023 and 7.9 g/L in 2022. It is possible that fruit chemistry was not impacted negatively (based on low GDD), because we had a low crop load due to winter injury. So there was less fruit to ripen in most varieties. We also like to think that our group did a good job with canopy management that enhanced fruit quality even in a cool year!
Table: 2023 Harvest fruit composition of selected grape varieties at the Wooster research vineyard: (2022 data)
***This factsheet can be found on Ohioline at https://ohioline.osu.edu/factsheet/plpath-fru-0052 or as a printable PDF online via the OSU Buckeye Appellation or Fruit Pathology websites.***
By: Melanie L. Lewis Ivey, Associate Professor, Department of Plant Pathology, OSU CFAES-Wooster Campus
Ripe Rot of Grape
Ripe rot is a late-season disease that primarily occurs in warm, moist, growing regions in the southeastern United States. However, outbreaks in Ohio and other states in the Midwest and Northeast occur when conditions are warm and wet during fruit maturation. The disease is caused by multiple species of the fungus Colletotrichum. Ripe rot reduces fruit yield and adversely affects the chemical composition and quality of grapes and wine, leading to undesirable flavors and color.
Disease Development and Symptoms
Ripe rot is caused by multiple species of the fungus Colletotrichum. In the spring, warm (77–86 degrees Fahrenheit /25–30 degrees Celsius) rains initiate the production and release of spores from tissues infected the previous season. Berries are susceptible to infections from bloom through harvest, but symptoms first appear just after veraison (the onset of ripening) and close-to-fruit maturity. Symptoms on berries of white-fruited cultivars first appear as reddish-brown circular lesions (Figure 1A) that can be mistaken for sunburn or chemical injury. The lesions expand in concentric circles until they cover the entire berry. As the berries rot, they become covered with black spots (fungal fruiting bodies or acervuli). During wet weather, the berries become covered with salmon-colored spore (conidia) masses (Figure 1B and 1C). Symptoms on red-fruited berries can be difficult to discern without the presence of spores and can be confused with sour rot (see PLPATH-FRU-50 Sour Rot Disorder of Grape). Rain spreads spores to other berries and clusters. The berries eventually shrivel into hard raisin-like structures called mummies, which usually remain attached to the berry cluster. Disease symptoms on the leaves, shoots, peduncles (cluster stems), or pedicels (berry stems) are not common. The fungus primarily overwinters on mummified berries and infected pedicels or peduncles, but also overwinters in woody tissues and dormant buds.
Figure 1. Ripe rot of white-fruited grape. Reddish- brown circular lesions on berries are the first symptoms of ripe rot (A). Berries covered in fruiting bodies of the ripe rot fungus (B). Salmon colored spores on the surface of a berry (C).
Management
Cultivar Selection
All cultivated grape (North American, V. vinifera, and interspecific hybrids of V. vinifera) varieties are susceptible to infection by the ripe rot fungus. However, some varieties appear to be more susceptible than others (Table 1). Susceptibility can vary from season to season.
Table 1. List of ripe rot susceptibility of common varieties grown in the Midwest and Northeastern United States1.
Resistant | Chardonel, Concord, Delaware, Ontario, Syrah |
Susceptible | Chambourcin, Chardonay, Marquette, Merlot, Niagara, Neptune, Sauvignon blanc, Seyval |
Highly Susceptible | Cabernet Franc, Cabernet Sauvignon, Carlos, Flame, Muscat, Golden Muscat, Petit Verdot, Vidal Blanc |
1Data from Shiraishi et al. 2007
Cultural Practices
Dormant season pruning to remove mummies can reduce the number of spores produced and released in the spring. Pruning debris should be removed from the vineyard before bud break, especially vineyards with a history of ripe rot.
Chemical Control
Fungicides applied early in the season, from bloom to three to four weeks after bloom, are effective at preventing infections and limiting late-season rot. If weather conditions favor disease development close to harvest (i.e., warm, wet, high humidity), additional fungicide applications are recommended. For late-season fungicide applications, always check the pre-harvest interval (PHI) of the fungicide to confirm that it can be used close to harvest.
Commercial growers can consult the Midwest Fruit Pest Management Guide (Bulletin 506) and/or Developing an Effective Fungicide Spray Program for Wine Grapes in Ohio (Plant Pathology Series No. 147) for current fungicide recommendations.
Backyard growers should integrate early-season fungicide application with cultural practices to control ripe rot disease. Ripe rot disease can be confused with other fruit rots, such as sour rot or black rot. Backyard growers are encouraged to contact the C. Wayne Ellett Plant and Pest Diagnostic Clinic (ppdc.osu.edu or 330-263-3721) for disease confirmation before making late-season fungicide applications.
Post-harvest Storage Practices
Grape clusters with ripe rot can negatively affect the quality and color of wine or juice. Fruit infected with ripe rot fungus that have not developed symptoms may develop symptoms during storage. To prevent rotting while in storage, sort out cracked, discolored, and rotting berries; place the berries in a breathable container; and store them at 30–32 F (-1–0 C).
Useful Resources
To learn more, check out Ohio State University Extension resources on ripe rot of grapes and related topics:
Developing an Effective Fungicide Spray Program for Wine Grapes in Ohio from Fruit Pathology Laboratory website from Ohio State University Extension at u.osu.edu/fruitpathology.
Sour Rot Disorder of Grape, (2021) from Ohio State University Extension’s Ohioline, at ohioline.osu.edu/factsheet/plpath-fru-50.
Midwest Fruit Pest Management Guide (OSU Bulletin 506) from Purdue Extension Education Store at ag.purdue.edu/department/hla/extension/sfg-sprayguide.
Reference
Shiraishi, M., Koide, M., Itamura, H., Yamada, M., Mitani, N., Ueno, T., Nakaune, R., and Nakano, M. 2007. Screening for resistance to ripe rot caused by Colletotrichum acutatum in grape germplasm. Vitis 46:196-200
By: Maria Smith, HCS-OSU
The new USDA plant hardiness zone maps have been updated for 2023 and were released this week. These updates occur approximately every 10 years, with the last maps released in 2012. The following press release from the USDA provides explanation for how the new zones are calculated and the 30-year timespan of winter minimum temperatures used to calculate the new zones.
These maps provide general guidance to new and existing grape growers to match vine cold tolerance with site conditions. HOWEVER, it should be noted that these zones are based on averages of winter minimum temperature, and mesoclimate conditions need to be accounted for in cultivar selection. As it is also stated in the press release and instructions for map use, winter extreme temperatures are variable and do dip below zone averages. In my 5 years at OSU, we have seen varying levels of winter injury in Vinifera in 2022, 2021, and 2019. And that does not include the polar vortex years of 2014 and 2015. All that to say, just because most of the state is now considered Zone 6a and 6b, does not necessarily indicate that Vinifera will survive at every site in every year. Choosing to plant Vinifera comes with significant risk of winter injury.
It is still best practice to track weather at your site to understand annual variation in weather conditions, be judicious in your cultivar selection, and plan to protect your grafted vines from winter injury.
You can use the interactive map to find your zone based on Zip code or download high-resolution copies of the map at https://planthardiness.ars.usda.gov/.
Figure 1. Ohio’s cold hardiness zones now include 5b (-15 to -10F), 6a (-10 to -5F), 6b (-5 to 0F), and 7a (0 to 5F).
Figure 2. Updated national map of USDA cold hardiness zones for 2023
USDA Unveils Updated Plant Hardiness Zone Map
Contact: Jan Suszkiw
Email: Jan.Suszkiw@usda.gov
WASHINGTON, DC, Nov. 15, 2023—The U.S. Department of Agriculture (USDA) today released a new version of its Plant Hardiness Zone Map (PHZM), updating this valuable tool for gardeners and researchers for the first time since 2012. USDA’s Plant Hardiness Zone Map is the standard by which gardeners and growers can determine which plants are most likely to thrive at a location. The new map—jointly developed by USDA's Agricultural Research Service (ARS) and Oregon State University's (OSU) PRISM Climate Group—is more accurate and contains greater detail than prior versions.
It is available online at https://planthardiness.ars.usda.gov/. In addition to the map updates, the Plant Hardiness Zone Map website was expanded in 2023 to include a “Tips for Growers” section, which provides information about USDA ARS research programs of interest to gardeners and others who grow and breed plants.
The 2023 map is based on 30-year averages of the lowest annual winter temperatures at specific locations, is divided into 10-degree Fahrenheit zones and further divided into 5-degree Fahrenheit half-zones. Like the 2012 map, the 2023 web version offers a Geographic Information System (GIS)-based interactive format and is specifically designed to be user-friendly. Notably, the 2023 map delivers to users several new, significant features and advances. The 2023 map incorporates data from 13,412 weather stations compared to the 7,983 that were used for the 2012 map.
Furthermore, the new map’s rendering for Alaska is now at a much more detailed resolution (down from a 6 ¼ -square-mile area of detail to a ¼ square mile). "These updates reflect our ongoing commitment to ensuring the Plant Hardiness Zone Map remains a premier source of information that gardeners, growers and researchers alike can use, whether they’re located in the continental United States, Alaska, Hawaii or Puerto Rico,” said ARS Administrator Dr. Simon Liu.
Approximately 80 million American gardeners and growers represent the most frequent users of the USDA Plant Hardiness Zone Map. However, they’re not the only ones with a need for this hardiness information. For example, the USDA Risk Management Agency refers to the map’s plant hardiness zone designations to set certain crop insurance standards. Additionally, scientists incorporate the plant hardiness zones as a data layer in many research models, such as those modeling the spread of exotic weeds and insects.
The 2023 Plant Hardiness Zone Map is now available as a premier source of information that gardeners, growers and researchers alike can use.
Plant hardiness zone designations represent what’s known as the “average annual extreme minimum temperature” at a given location during a particular time period (30 years, in this instance). Put another way, the designations do not reflect the coldest it has ever been or ever will be at a specific location, but simply the average lowest winter temperature for the location over a specified time. Low temperature during the winter is a crucial factor in the survival of plants at specific locations.
As with the 2012 map, the new version has 13 zones across the United States and its territories. Each zone is broken into half zones, designated as “A” and “B.” For example, zone 7 is divided into 7a and 7b half zones. When compared to the 2012 map, the 2023 version reveals that about half of the country shifted to the next warmer half zone, and the other half of the country remained in the same half zone. That shift to the next warmer half zone means those areas warmed somewhere in the range of 0-5 degrees Fahrenheit; however, some locations experienced warming in the range of 0-5 degrees Fahrenheit without moving to another half zone.
These national differences in zonal boundaries are mostly a result of incorporating temperature data from a more recent time period. The 2023 map includes data measured at weather stations from 1991 to 2020. Notably, the 2023 map for Alaska is “warmer” than the 2012 version. That’s mainly because the new map uses more data representing the state’s mountain regions where, during winter, warm air overlies cold air that settles into low-elevation valleys, creating warmer temperatures.
The annual extreme minimum temperature represents the coldest night of the year, which can be highly variable from year to year, depending on local weather patterns. Some changes in zonal boundaries are also the result of using increasingly sophisticated mapping methods and the inclusion of data from more weather stations.
Temperature updates to plant hardiness zones are not necessarily reflective of global climate change because of the highly variable nature of the extreme minimum temperature of the year, as well as the use of increasingly sophisticated mapping methods and the inclusion of data from more weather stations. Consequently, map developers involved in the project cautioned against attributing temperature updates made to some zones as reliable and accurate indicators of global climate change (which is usually based on trends in overall average temperatures recorded over long time periods).
Although a paper version of the 2023 map will not be available for purchase from the government, anyone may download the new map free of charge and print copies as needed.
The Agricultural Research Service is the U.S. Department of Agriculture's chief scientific in-house research agency. Daily, ARS focuses on solutions to agricultural problems affecting America. Each dollar invested in U.S. agricultural research results in $20 of economic impact.
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.
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.
Weather:
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.
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 (https://weather.cfaes.osu.edu)
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:
Diseases:
- 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).
Insects:
- 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.
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.
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.
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 (https://weather.cfaes.osu.edu).
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.
Fig 3. Ohio drought status, 27 June 2023. From https://droughtmonitor.unl.edu/
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.
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!
Fig. 6 Air quality from 28 June 2023. Figure from www.airnow.gov
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.
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.
Figure 2. Primary and secondary shoot emergence from single node position
Weather
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.
Figure 3. Wooster, OH cumulative GDD (base 50F) as of May 16 = 372, historic GDD for May 16 = 383. Chart from CFAES Weather System (https://weather.cfaes.osu.edu)
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.
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) |
31.6 |
29.6 |
Avon Lake (North Central) |
32.5 |
30.9 |
Caldwell (Southeast) |
27.7 |
35.7 |
Cincinnati (Southwest) |
31.0 |
44.0 |
Columbus (Central) |
31.5 |
36.9 |
Fremont (Northwest) |
30.7 |
29.4 |
Piketon (Southcentral) |
25.5 |
35.7 |
Wooster (Northeast) |
26.1 |
27.2 |
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) |
|
|
°F |
°C |
Dormant bud |
6.8 |
-14 |
Swollen bud stage |
25.9 |
-3.4 |
Bud burst (break) |
28.0 |
-2.2 |
First unfolded leaf |
28.4 |
-2.0 |
Second unfolded leaf |
28.9 |
-1.7 |
Fourth unfolded leaf |
29.8 |
-1.2 |
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.
- 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.
- 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.
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.
Grape Type |
Pruning Formula |
Cluster Thinning |
American |
30 + 10 |
No |
French Hybrids |
20 + 10 |
Yes |
New Hybrids |
20 + 20 |
No |
Seedless Table |
30 + 10 |
Yes |
Vinifera |
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 |
Adjustment |
0 to 14% |
No adjustment needed |
15 to 34% |
Retain an extra 35% buds |
35 to 50% |
Retain an extra 50% buds |
>50% |
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.