IMPROVING GRAPEVINE PRODUCTIVITY-MITIGATING ARMILLARIA ROOT DISEASE

Authors: Baumgartner, Kendra; Warnock, Amy

Submitted to: Practical Winery and Vineyards
Publication Type: Trade Journal
Publication Acceptance Date: 2/1/2005
Publication Date: 3/1/2005
Citation: Baumgartner, K., Warnock, A.E. 2005. Improving grapevine productivity-mitigating armillaria root disease. Practical Winery and Vineyards.

Interpretive Summary: Grapevines can tolerate Armillaria root disease and remain productive if the rate of infection by the pathogen, Armillaria mellea, is slowed down. The goal of the preliminary research reported here was to evaluate the efficacy of Vesta' (Biologically Integrated Organics, Inc., Sonoma, CA), an organic soil inoculant, to improve growth and yield of infected vines. An experiment was designed to test Vesta as a therapeutic treatment (a product applied to a disease plant in an attempt to prolong its life). We focused on vines with moderate symptoms, as they are more likely to benefit from a therapeutic treatment than severely symptomatic vines because they still have some capacity for root growth. Research was conducted in two North Coast vineyards, both with Armillaria root disease, but with different mortality rates. The Napa vineyard was planted in 1997 and had fewer dying vines (2% of all vines die from Armillaria root disease per year). The Sonoma vineyard was planted in 1991 and had a mortality rate of 10%. Vesta was applied through the drip-irrigation system four times during the growing season. Vesta had no effect on yield or growth of healthy vines, but it did improve yields of symptomatic vines in the Napa vineyard. It increased yields of symptomatic vines by 22%. Cluster weights of symptomatic-treated vines were as high as that of healthy vines. Vesta had no effects on yield or growth in the Sonoma vineyard, likely due to the higher infection rate among vines in this vineyard. Vesta appears to be a promising approach to control Armillaria root disease, as long as vineyards are treated soon after the disease is diagnosed. Focusing control efforts on infected grapevines that still produce normal clusters is a cost-effective strategy, given that replants are not immediately productive and are likely to become infected by the fungus.

Technical Abstract: Grapevines can tolerate Armillaria root disease and remain productive if the rate of root collar infection by Armillaria mellea is decreased early in the infection process. The goal of the preliminary research reported here was to evaluate the efficacy of Vesta' (Biologically Integrated Organics, Inc., Sonoma, CA), an organic soil inoculant, to improve growth and yield of infected vines. An experiment was designed to test Vesta as a therapeutic treatment (a product applied to a disease plant in an attempt to prolong its life). We focused on vines with moderate symptoms, as they are more likely to benefit from a therapeutic treatment than severely symptomatic vines because they still have some capacity for root growth. Research was conducted in two North Coast vineyards, both with Armillaria root disease, but with different mortality rates. The Napa vineyard was planted in 1997 and had a mortality rate of 2%. The Sonoma vineyard was planted in 1991 and had a mortality rate of 10%. Vesta was applied through the drip-irrigation system at budbreak, full bloom, 15% veraison, and 85% veraison. Vesta had no effect on yield or growth of healthy vines, but it did improve yields of symptomatic vines in the Napa vineyard. It increased yields of symptomatic vines by 22%. Cluster weights of symptomatic-treated vines were as high as that of healthy vines. There were no significant effects of Vesta on yield or growth in the Sonoma vineyard, likely due to the higher infection rate among vines in this vineyard. Vesta appears to be a promising approach to control Armillaria root disease, as long as vineyards are treated soon after the disease is diagnosed. Focusing control efforts on infected grapevines that still produce normal clusters is a cost-effective strategy, given that replants are not immediately productive and are likely to become infected by the fungus.