Location: Crops Pathology and Genetics Research
Project Number: 2032-21220-007-10-T
Project Type: Trust Fund Cooperative Agreement
Start Date: May 1, 2018
End Date: Apr 30, 2019
Objective(s) of Proposed Research: 1. Evaluate spray applications of pruning-wound protectants for trunk-disease prevention. 2. Identify Esca pathogens, with a focus on Basidiomycete wood-rotting fungi. 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.
For Objective 1, we will test the efficacy of three fungicide treatments (Topsin + Rally, Luna Experience, Pristine) and one biological control (Serifel) to protect pruning wounds from infection by trunk pathogens. Our replicated field experiment was established in 2017 in a Scarlet royal vineyard planted April 2015. We propose to continue this experiment. Vines are spur-pruned in late January and treated by spray application with a tractor. Within 24 h 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) are inoculated with trunk pathogens causing Botryosphaeria dieback (causal fungus Neofusicoccum parvum), Eutypa dieback (Eutypa lata), Phomopsis dieback (Diaporthe ampelina), or Esca (Phaeomoniella chlamydospora). Non-inoculated spurs are 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 qPCR. For Objective 2, our goal is to determine which Esca pathogens attack table grapes, so all species can be considered in table grape research, for e.g., in field trials on trunk-disease management. We plan to sample vineyards (10 per county) ages 10 to 15-years-old within Fresno, Kern, Kings, and Tulare Counties. Because the industry harvests the greatest number of tons from ‘Scarlet Royal’, ‘Autumn King’, and ‘Flame Seedless’, sampling will be narrowed to these cultivars (10 vineyards per each of four counties, consisting of any combination of the following cultivars: ‘Scarlet Royal’, ‘Autumn King’, or ‘Flame Seedless’).