From the Lab to the Field: Improving Biocontrol Strategies Against Trunk Diseases in Vineyards. AVF Project #2024-2689.

Summary of Progress:

Multiple strategies involving biocontrol agents and fungicides were evaluated for their efficacy in managing grapevine trunk diseases. Treatments were applied in three ways: (i) as pruning wound protectants, (ii) as dips for propagation material before grafting in nurseries, and (iii) as soil drenches. This report presents findings from the third year of experiments.

As pruning wound protectants, certain fungicides, including Topsin M, significantly reduced infection rates of Neofusicoccum parvum and Diplodia seriata compared to untreated controls and other treatments. In nurseries, pre-grafting applications of select fungal and bacterial biocontrol agents improved callus formation at both the graft union and the rootstock. While Topsin M and some biofungicides effectively reduced lesion length and N. parvum infections, they did not prevent lesion development caused by Eutypa lata or Phaeoacremonium minimum. However, both biological and fungicidal treatments were effective in reducing necrosis length and E. lata recovery.

Soil drench applications yielded significant reductions in necrosis caused by E. lata and in P. minimum recovery from cordons. Collectively, these findings indicate that biocontrol strategies positively impact grapevine trunk disease management under California field conditions. Nevertheless, further validation in commercial vineyards is needed to generate practical data for integrating these methods into IPM programs.