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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).