Shoot thinning, or removal, is an essential practice in vineyard management. This process involves selectively removing some of the new growth (shoots) during the growing season. This is typically done in late spring or early summer, once the shoots have begun to grow but before they’ve become woody canes.
The reasons for shoot thinning in mid-season include:
- Balancing the Vine: Overcrowded vines tend to produce a larger quantity of lower-quality grapes. By thinning the shoots, the energy of the vine is directed towards a smaller number of shoots, potentially improving grape quality.
- Improving Air Circulation and Sunlight Exposure: Dense foliage can prevent sunlight from reaching the grape clusters, impacting grape ripening and sugar development. It can also trap moisture, which increases the risk of fungal diseases. Thinning shoots can help ensure that more sunlight reaches the grape clusters and that there’s good air circulation, reducing disease risk.
- Managing Vine Vigor: In vigorous vines, excess shoot growth can lead to an imbalance between vegetative growth (leaves and shoots) and reproductive growth (grape clusters). By removing some shoots, the vine’s vigor can be managed, maintaining a balance between vegetative and reproductive growth.
- Improved spraying for crop protection: Better shoot and canopy management leads to improved chemical product penetration and coverage in the grapevine foliage.
Thinning: A non-trivial task
The practice of shoot thinning in wine grape vineyards is crucial. But, the need for shoot thinning can be considerably reduced if the number of buds retained during dormant pruning aligns with the desired number of shoots, and if cane pruning is preferred over spur pruning. Shoot emergence is not homogenous across the field, and this variability can play a critical role in the estimation of labor demands. Of all the canopy management procedures, shoot thinning is perhaps the most time-sensitive. There exists a brief window to thin shoots before the labor required for this task increases dramatically. According to studies, manual shoot-thinning costs can reach up to $1482/ha .
As such, it is strongly recommended to begin shoot thinning as early as feasible in the growing season, as soon as the fruit-bearing capacity of the shoots can be assessed. An early start to shoot thinning ensures the retention of only the desired number of fruit-bearing shoots, setting the groundwork for the successful growth of a healthy canopy and a high-quality crop with lower susceptibility to fungal diseases .
Assessing variability and individual shoot-thinning needs can be labor intensive, requiring good knowledge from the field workers. The Viewer system employs cutting-edge image technology to analyze the shoot population density and accurately count shoots in every grapevine tree. The system can be mounted on the tractor and execute monitoring tasks, while farmers conduct seasonal field activities (e.g, spraying). Upon completion of the operation, Viewer will instantly publish field observations and shoot count maps in Viewer’s web Dashboard. Farmers can then monitor regions with low/high shoot populations at different growth stages, and proactively plan shoot-thinning tasks and reduce labor demand.
- Early season grapevine canopy management, Part I: Shoot thinning, Penn State Extension Wine & Grapes U. Maria Smith and Dr. Michela Centinari, Dept. of Plant Science (link)
- Kurtural, S. K., & Fidelibus, M. W. (2021). Mechanization of pruning, canopy management, and harvest in winegrape vineyards. Catalyst: Discovery into Practice, 5(1), 29-44.
- Vineyard Canopy Management: Shoot Thinning.
Cain Hickey, Timothy Coolong, University of Georgia extension (link).