Location: Crops Pathology and Genetics Research
Project Number: 2032-21220-008-17-T
Project Type: Trust Fund Cooperative Agreement
Start Date: May 1, 2019
End Date: Oct 31, 2020
Trunk diseases are best managed when vineyards are young, before infections are established. Preventative applications of pruning-wound protectants may minimize infections and thus prevent the severe yield losses that typically occur when trunk diseases go unmanaged. Protectants have been evaluated in field trials on wine grapes, but not on table grapes. Our goal is to determine which protectants are most effective. Summer 2017 was notable for numerous statewide reports of the Esca symptom known as ‘apoplexy’, when entire vines wilt and die from this trunk disease. These reports opened our eyes to gaps in the research on Esca (aka Measles), relative to other trunk diseases. We aim to fill these gaps, so we can make accurate recommendations to growers about managing all trunk diseases, including Esca.
We will test the efficacy of two fungicides (Topsin, Pristine), both with and without the surfactant Pentrabark, to protect pruning wounds from infection by trunk pathogens. Our replicated field experiment will be established in 2020. Vines will be pruned in late January and treated by spray application with a tractor. Within 24 hours of rain following application, the spurs of eight vines per data row (four data vines at start of row, four data vines half-way down the row) will be inoculated with trunk pathogens causing Botryosphaeria dieback (causal fungus Neofusicoccum parvum), Phomopsis dieback (Diaporthe ampelina), or Esca (Fomitiporia polymorpha and Phaeomoniella chlamydospora). Non-inoculated spurs will be used as controls, to determine background levels of trunk pathogens. Before budbreak, inoculated spurs are collected and brought back to the lab to recover the pathogens in culture and quantitative polymerase chain reaction (qPCR).