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By: Imed Dami, HCS-OSU
In early June, members of the OSU Grape Team, Andy Kirk, AARS manager and Andrew Holden, Extension educator, visited vineyards in Lake and Ashtabula counties (NE-OH) and reported extensive cold injury ranging from bud to trunk injury (Figure 1). The cold events (temperature in low to high-20s) at the end of April were initially to blame. Even though these temperatures are lethal to young emerging shoots as it was observed in central and southern Ohio, this was not the case in northern Ohio since most buds were still closed. Therefore, we suspect that previous and successive cold events since January through March were the culprit for the extensive damage. The warm spells in late February and early March accelerated the timing and magnitude of deacclimation (loss of cold hardiness). Figure 2 shows the minimum temperatures in January that ranged between 0 and -11F. I doubt those temperatures had caused extensive damage in most varieties (except the most tender vinifera). So the extensive damage is unlikely from the January events. Figure 4 shows the lowest temperatures in late April that occurred mostly in NE-OH. Those temperatures may be lethal to early bud-breaking varieties, but most varieties did not break buds yet in late April. Figure 3 shows the lowest temperatures in March that ranged between 13.6 and 20.6F. Those temperatures likely caused the extensive damage. Figure 5 shows daily minimum and maximum temperatures of 2021 and 2022 at the AARS in Kingsville. Note warmer February in 2022 than 2021, and peaks of maximum temperatures (70s) in mid-March followed by sudden drop to 15.2F then 18.3F at the end of the month. Even though we don’t know the level of deacclimation in each variety, the low temperatures in the mid-teens were likely lethal. Furthermore, there was a large swing of temperature from 85.3F on April 24th to 28.2F on April 29th, which could have been damaging to buds in the early stages of development. Maria Smith and Andy Kirk also observed more damage in low lying vineyards and those with southern aspects (exposure), which tend to intensify deacclimation (due to excess heat accumulation) and hence exacerbate cold damage.
Regardless of the origin of the damaging cold events, vines sustained shoot damage, bud damage, or damage to the vascular tissues (cane, cordon, trunk). The following section describes the steps to take to address each type of cold damage.
Managing cold damage of frosted shoots: recommendations for managing the vineyard in the event of frost damage can be found in the APRIL 2020 OGEN.
Managing trunk damage: It is an ideal time now to assess trunk damage. The abundance of sucker growth is an indication of trunk damage. In 2014-2015, we experienced one of the worst cold damages to vineyards across Ohio. We conducted several trials to determine the best management practices after cold injury. The following are highlight of our findings and recommendations:
- Train all suckers (Figure 6) produced by each vine. Do not keep 2 suckers per vine as this would promote bull growth in mature vines which is undesirable.
- Fan training (Figure 7): suckers can be trained vertically and onto a fan shape. Shoots can be kept straight by tucking them between the catch wires. This training promotes good exposure of shoots to sunlight and good penetration of fungicides. Labor is also minimized with this training as vines do the training by themselves.
- Dead trunks and cordons can be removed with loppers during this season. Cut back trunks to 6-8” stumps to avoid fungal disease infection caused by Eutypa and other pathogens. Stumps can be removed later in the summer.
- No need to train shoots to horizontal position to establish cordons for next season. It is best to save this job for next season when pruning.
- Next year when pruning, you could select the best two canes as your new trunks. These canes will have medium size diameter, fully hardened-off, and disease-free. Remove bull canes. The optimum-sized canes can be laid down on the fruiting wires to establish the new cordons. Once laid down, cut back each cane to about 24” (or 10-12 buds, whichever is the shortest) in each side. This practice would avoid apical dominance growth.
Finally, make sure you contact your local FSA representative and report damage. You need to document the damage. In 2014, we developed a factsheet that shows different types of vine damage. Please visit this link Assessing cold damage in early summer to read or download. It is also used by FSA reps to assess freeze damage.
As always, please do not hesitate to contact our Grape Team (Gary Gao, Andy Kirk, Maria Smith and Imed Dami) if you have any questions regarding managing vines after cold damage.
Figure 1. Cold damage of Cabernet franc grapevine grown in NE-OH. Note growth of suckers at the vine base. Photo by: Maria Smith.
January 2022 Minimums
Figure 2. Minimum temperatures in January 2022 and corresponding dates of occurrence in parentheses. Note that minimum temperatures ranged between 0 and -11F with lowest in northern Ohio (west to east). Source: Dr. Aaron Wilson, OSU state climatologist.
Figure 3. Minimum temperatures in late March 2022 and corresponding dates of occurrence in parentheses. Note that minimum temperatures ranged between 13.6 and 20.6F with lowest in NE-OH. Source: Dr. Aaron Wilson, OSU state climatologist.
Figure 4. Minimum temperatures in late April 2022 and corresponding dates of occurrence in parentheses. Note that minimum temperatures ranged between 24.7 and 34F with lowest in NE-OH. Source: Dr. Aaron Wilson, OSU state climatologist.
Figure 5. Daily minimum and maximum temperatures in 2021 and 2022 at the AARS in Kingsville.
Figure 6. Sucker growth is an indication of trunk injury. Keep all suckers when retraining new trunks for following season.
Figure 7. Suckers of Cabernet franc trained on fan shape system during summer after trunk cold injury.