When it comes to detecting and treating vineyards for grapevine canker diseases (also called trunk diseases), like Botryosphaeria dieback (Bot canker), Esca, Eutypa dieback and Phomopsis dieback, the earlier the better, says plant pathologist Kendra Baumgartner, with the USDA’s Agricultural Research Service, based at the University of California, Davis. That’s why she’s leading a team of researchers and UC Cooperative Extension specialists and farm advisors to develop tools that will enable growers to do just that.


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These trunk diseases are triggered by rain splash which disperses fungal spores that enter the vine through wounds left by pruning or other injury. Typically, growers take action to control these disease once they begin seeing symptoms in the field. Usually, though, those signs aren’t apparent until the vines are about seven to eight years old. By then, the diseases may have been festering inside healthy-looking wood for several years, starting the vineyard on a slow, steady decline in grape yields and quality. While various treatment practices at this point can prevent infection of pruning wounds, they won’t eradicate wood cankers from already infected vines, which slowly succumb to the effects of the disease. Eventually, productivity drops to uneconomic levels.

Baumgartner’s team is working on field and laboratory techniques that would offer growers a simple, quick way to identify canker diseases on vines as young as, say, three years. It would involve placing traps in the vineyard to collect fungal spores following a rain event and sending them to a lab for analysis. Researchers currently use spore traps to study powdery mildew infections in vineyards. Baumgartner’s team is developing new, relatively easy-to-perform lab procedures for analyzing the ‘trap catches’ that would identify any disease spores within a day.

“Rather than having to wait until 20 percent to 25 percent of their vineyard is infected before they even know they have the disease, growers would be able to start treating their vines before the diseases get a good foothold,” she says.  “As a result, instead of having to pull out a diseased vineyard after just 15 or 20 years, the vineyard would remain productive for much longer.”