Double pruning to prevent trunk diseases in Washington vineyards

Authors: KAPLAN, JONATHAN - California State University; TRAVADON, RENAUD - University Of California; Baumgartner, Kendra

Submitted to: Trade Journal Publication
Publication Type: Trade Journal
Publication Acceptance Date: 9/19/2014
Publication Date: 9/19/2014
Publication URL: http://wine.wsu.edu/research-extension/files/2010/07/2014-Fall-VEEN-Final.pdf)
Citation: Kaplan, J., Travadon, R., Baumgartner, K. 2014. Double pruning to prevent trunk diseases in Washington vineyards. Trade Journal Publication.

Interpretive Summary: Trunk diseases (aka wood-canker diseases) present a serious challenge to the productive life of a vineyard. The four main trunk diseases are Botryosphaeria dieback, Esca, Eutypa dieback, and Phomopsis dieback. They cause the shoots to die before reaching a healthy size and eventually kill off the spur positions from which the shoots grow. The fungi that cause these diseases permanently infect the grapevine wood. There is nothing you can spray on the outside of the vine to kill them, once they are inside the wood. The most effective tactic is disease prevention. One effective practice is double pruning, which involves pruning twice: the first pruning cuts down to 10 to 12-inch long canes are made in December, the second (final) cuts down to the spurs are made in March. To better understand the potential gains from early adoption of double pruning in Washington vineyards, we apply the same mathematical formulas we used previously for economic analyses of California vineyards, but with management and grape figures for Washington. We focus on double pruning because many Washington growers already use this practice to protect from winter damage. Adopting double pruning in years 3 or 5 increases annual positive net returns to twice that of waiting until year 10, at which point yield losses are already beyond 20%. The exception is Chardonnay, for which double pruning never produces positive net returns, regardless of the age of the vineyard when you start using this practice. White Riesling and Cabernet Sauvignon vineyards fare best, producing positive net returns when adopted in years 3 or 5, even if the dominant trunk disease is Esca, for which double pruning is least effective. Our economic analyses also estimate that double pruning increases the number of profitable years of production than if no action is taken, the latter of which gives only 10 (for Chardonnay and Merlot) or 11 (for White Riesling and Cabernet Sauvignon) profitable years. If adopted in years 3 or 5, double pruning can extend the profitable lifespan of a vineyard by as much as 100%, depending on the trunk diseases. These results present a convincing argument for adopting double pruning in young vineyards, and not waiting until symptoms appear in years 8 to 10.

Technical Abstract: Trunk diseases (aka wood-canker diseases) present a serious challenge to vineyard productivity and longevity. There are four main trunk diseases: Botryosphaeria dieback, Esca, Eutypa dieback, and Phomopsis dieback. The causal fungi (e.g., Eutypa lata, Neofusicoccum parvum) establish chronic infections of the cordons, spurs, and trunk. This results in stunted shoots, shoot dieback, and dead spurs, which are general symptoms for all trunk diseases. The cumulative yield losses, mainly from the dead spurs, build to the point at which management costs outweigh vineyard returns. The most effective trunk disease management practices are preventative. To better understand the potential gains from early adoption of the preventative practice of double pruning in Washington vineyards, we apply the economic analyses we used previously for California vineyards. We focus on double pruning because many growers already use this practice to protect from winter damage. The economic gains from adopting in years 3 or 5, in terms of positive net returns on an annual basis, are in many cases double that of waiting until year 10. The exception is Chardonnay, for which double pruning does not produce positive net returns, regardless of vineyard age. White Riesling and Cabernet Sauvignon vineyards fare best, producing positive overall net returns when adopted in years 3 or 5, even if the dominant trunk disease is Esca, for which double pruning is least effective. Our economic analyses estimate that double pruning results in more profitable years of production than if no action is taken, the latter of which gives only 10 (for Chardonnay and Merlot) or 11 (for White Riesling and Cabernet Sauvignon) profitable years. If growers adopt in years 3 or 5, they can extend the profitable lifespan of a vineyard by as much as 100%, depending on the trunk diseases present. These results present a convincing argument for adopting double pruning in young vineyards, and not waiting until symptoms appear in years 8 to 10.