Progress report for ONC23-133
Project Information
Several cold-hardy wine grape cultivars have been released from breeding programs. These cultivars are the base of wine grape industry in many states in the North Central Region. While their cold hardiness and wine quality have been researched and reported, few research-based cultivar specific viticulture practices have been investigated.
Growers of cold-hardy grapes generally live in regions of abundant rainfall, which predisposes vines to fungal infections. Differing pruning methods can be used, which can impact vineyard yield and predisposition to disease carryover. Pruning is one of the more labor-intensive practices in growing grapes. Grapevine trunk diseases are increasing in prevalence, which has reduced the recommended timeframe to prune. Additionally, labor is increasingly difficult to source, so growers are looking to mechanize what vineyard practices they can.
This project will investigate pruning to canes and differing spur lengths to determine what impact this may have on yield, fruit quality, canopy, and incidence of disease. Partial and full mechanical vineyard management will be trialed in comparison with hand management to determine what impact this may have on the fruit and vine characteristics. This will provide growers with information to make informed decisions on how to prune these relatively new grape cultivars.
- Quantify fruitfulness of nodes of recently introduced cold-hardy grape cultivars at locations along canes.
- Develop pruning recommendations for recently introduced cold-hardy grape cultivars.
- Evaluate potential for mechanically pruning cold-hardy grape cultivars on high wire cordon training systems.
- Compare disease infection incidence between mechanically pruned and hand pruned vines.
- Familiarize growers of cold-hardy grape cultivars with successful and scalable mechanical pruning options.
Cooperators
Research
Location 1:
Work at this location was done with the grape cultivar 'La Crescent'. This vineyard is hand harvested, which allowed us to apply the treatments to replicated panels within the same row. Vines were pruned to 50 buds using 5 treatments: either 2-, 3-, 4-, or 5-node spurs, and four 10 to 15-node canes. The treatments are applied to panels of 3 vines, and replicated 3 times for a total of 45 vines. Vines with a pruning weight of less than 0.5 lbs were not included in the results due to low vigor. Commercial practices for canopy and pest management were applied during the growing season. Harvest occurred when the ideal parameters for wine production were met. Yield, brix, pH, and titratable acidity were recorded.
Location 2:
Work at this location was done with 'Brianna' and 'Marquette'. Vines were pruned to 50 nodes. Treatments included pruning to 4 treatments: 2-, 3- , or 5-node spurs, and four long 10 to 15-node canes on 4 rows of each cultivar, ~50 vines per row. Commercial practices for canopy and pest management were applied during the growing season. Machine harvest occurred when the ideal parameters for wine production were met. Rows were hand subsampled prior to machine harvest and yield, brix, pH, and titratable acidity were recorded. Yield, brix, pH, and titratable acidity were recorded for mechanical harvested samples.
Location 3:
Work at this location was done with 'Frontenac Gris'. Vines were pruned in 3 different methods: hand prune to 50 nodes, 2 passes with a VineTech Concord Pre-Pruner mounted on a skid steer, and one pass with the mechanical pre-pruner with a hand pruning follow up with ~12 major cuts, on 6 rows of each cultivar, ~50 vines per row. The shoots located on two spurs per vine were assessed for what percent of leaves on the shoot were infected (incidence) and the infected leaves were rated on a scale of 1-4. A '1' was assigned to leaves with little to no foliar lesions and a '4' was the highest rating for substantial infections. There were minimal cluster infections, so that was not recorded. Commercial practices for canopy and pest management were applied during the growing season. Machine occurred when the ideal parameters for wine production were met. Rows were hand subsampled prior to machine harvest brix, pH, and titratable acidity were recorded. Yield, brix, pH, and titratable acidity were recorded for mechanical harvested samples.
Results
Location 1:
From year 1 of the study 'La Crescent' grapevines yield more on longer spurs than shorter spurs. Cane pruning yielded the lowest. There did not appear to be variability in the fruit chemistry (Table 1).
| Table 1: La Crescent | ||||
| Pruning Type | Yield/Vine (lbs) | Brix | pH | TA (g/L) |
| 4 Canes | 17.5 | 21.9 | 3.10 | 12.3 |
| 2-node Spurs | 20.0 | 21.9 | 3.09 | 11.7 |
| 3-node Spurs | 21.7 | 22.1 | 3.09 | 12.1 |
| 4-node Spurs | 22.0 | 21.7 | 3.07 | 12.5 |
| 5-node Spurs | 23.1 | 21.5 | 3.10 | 12.3 |
Location 2
From year 1 of the study 'Brianna' grapevines yielded more from cane pruning, and yield decreased with spur length. Higher yielding cane pruned vines appear to have a lower brix and pH compared with lower yielding 2-node pruned vines. (Table 2). Unfortunately the mechanical harvester broke down halfway through the 'Marquette' harvest, so the harvest values can not be directly compared due to differing harvest dates of around 5 days. We hand harvested and sampled 8% of the vines prior to the machine harvest and we are processing that fruit to determine what impacts the treatments had, however large variability exist in vines within a vineyard.
| Table 2: Brianna | ||||
| Pruning Type | Yield/Vine (lbs) | Brix | pH | TA (g/L) |
| 4 Canes | 24.6 | 16.5 | 3.21 | 7.1 |
| 2-node Spurs | 16.0 | 18.6 | 3.31 | 6.6 |
| 3-node Spurs | 20.0 | 18.2 | 3.16 | 8.1 |
| 5-node Spurs | 20.3 | 17.3 | 3.23 | 6.7 |
Location 3:
Hand pruned vines took nearly eight times as long to prune as 2 passes from the mechanical pre-pruner, and around 3 times longer than mechanical pruning with a hand follow up (Table 3). It appears that hand pruned vines yielded slightly more than mechanically pruned vines, while fruit chemistry of the higher yielding hand pruned vines may have had a somewhat lower brix. Black rot was present in the foliage. While the incidence on the vine does not appear to be impacted by the pruning method, the hand pruned vines appear to have a lower level of infection severity.
| Table 3: Frontenac Gris | |||||||||
| Black Rot Infections | |||||||||
| 26-May-23 | 15-Jun-23 | Pruning | |||||||
| Pruning Type | Brix | pH | TA (g/L) | Yield/Vine (lbs) | Severity | incidence | Severity | incidence | Labor (min) |
| Hand | 21.7 | 3.04 | 10.4 | 18.7 | 1.1 | 87% | 1.1 | 54% | 3.63 |
| Mechanical & Hand | 22.1 | 3.06 | 10.1 | 17.5 | 1.8 | 99% | 1.3 | 50% | 1.16 |
| Mechanical | 22.7 | 3.06 | 10.0 | 17.2 | 2.3 | 100% | 2.3 | 49% | 0.46 |
Discussion
Caution needs to be made in interpreting the data from only 1 year. From year 1 of the study, 'La Crescent' appears to yield best when pruned to longer spurs, but long canes did not yield as well. This could indicate that the nodes past node 5 are less productive or that non-count shoots arising from the cordons on the spur pruned vines contributed to the yield. It did not appear that fruit chemistry was impacted by the pruning methods. 'Brianna' vines yielded more as the spur or cane length increased. Fruit ripening was delayed for the higher yielding cane pruned vines, when compared with the lower yielding 2-node spur vines. So, if higher brix is the goal of the grower, they can either adopt pruning to short spurs, or prune to longer spurs or canes, and delay harvest to a later date.
For the machine pruned vines, the non-selectivity of mechanical pruning appears to have lead to a lower yield in year 1 and the additional step of mechanical pruning with a hand follow up had a similar yield to mechanical pruning alone. The mechanical pruner can be adjusted to leave more buds per vine if desired to offset these lower yields. The brix appears somewhat higher on the mechanically pruned vines, but this could be the result of the lower yield. It does appear that mechanical pruned vines had a higher disease severity when compared with hand pruned vines, this is likely due to old wood, dead wood, cluster rachises, etc. persisting and providing more inoculum in the mechanically pruned vines. But all treatments had roughly the same incidence of leaves that were infected. It does appear that mechanically pruned vines with a hand pruning follow up can reduce disease severity when compared with only mechanical pruning, due to the removable of less than ideal wood from the vines. Labor savings over hand pruning can be realized with mechanical pruning only or mechanically pruned vines with hand follow up. While not within the scope of this work, the additional step of mechanical pruning with a hand follow up, may lead to labor savings in the future as old wood accumulates in the only machine pruned vines. Additionally this was a dry growing season, and in a wet growing season, differences in disease may be more pronounced.
Educational & Outreach Activities
Participation Summary:
Growers have begun to contact the PI regarding pruning questions, which relate to the information in this study.
We shared information about the mechanical pruning plots in the Iowa State University Viticulture Newsletter and showed some video about our plots on social media.
We initially were going to have events in 2023, but decided that there would be a greater impact if we waited until we had data from the study to have those events. We are currently planning an event for March 2024 at the location that demonstrates the comparison between hand and mechanical pruning. In June of 2024 we are planning a field day at one of the plot locations which compares cane and spur pruning. Our vineyard mechanization tour is being planed for late July of 2024.
Videos showing the plots in more detailed are being developed and will be shared in the near future.
Learning Outcomes
Labor efficiency of mechanical pruning compared with hand pruning.
How cane/spur length can impact vineyard yield and therefor fruit ripening.
Project Outcomes
Total outcomes are yet to be determined as the major outreach events will be occurring in 2024. We caution the over interpretation of the results of one year of information on woody perennial crops.
Results from year 1 have provided growers with the potential labor savings benefits of mechanical pruning when compared with hand pruning, but also some of the potential risks which include potential increases in fungal disease infection severity. Growers can determine if the positives outweigh the negatives from a financial and pest risk perspective.
Pruning method appear to impact cultivars differently. Pruning is one of the more labor intensive practices in grape production. By adjusting our pruning practices for each cultivar growers may see increased yield which increases the economic viability of wine grape production of cold hardy grapes, but this may results lower brix at harvest. This can impact the marketing of the fruit, or time of harvest may need to be adjusted to compensate.