“We recommend taking steps to prevent trunk diseases when vineyards are very young,” Bettiga says. “Prune late in the dormant season, preferably February or later.”

The idea is to avoid leaving the vine vulnerable to high spore loads released from the first fall rains, he notes. Also, pruning wounds made then take longer to heal than those made in late dormancy when warmer temperatures encourage more vine growth and faster healing.

Keep in mind that wounds from pruning cuts made to canes or larger cuts made to re-position/re-orient spurs also provide an opening for fungi to enter the vine.

Bettiga advises continuing these pruning practices even in diseased mature vineyards. Because wood cankers are very localized, the more wounds you protect, the fewer new cankers that develop each year. That, in turn, means fewer dead spurs, arms or canes over time.

Treat wounds with a protectant, such as a registered fungicide or an organic sealant material. Because a vineyard may be infected with more than one type of trunk disease, Bettiga recommends combining fungicide products with different modes of action for a broader spectrum of control.

Also, don’t delay treatment. “As soon as you finish pruning a block, treat it that same day,” he says.

Once a vine becomes infected with a trunk diseases, the only way to control the disease is to cut out infected parts of the vine and re-train it.

“If you catch the disease early enough before it progresses too far down the trunk, you can cut off infected parts of the cordon or prune infected wood from the trunk until you get to clean wood,” he says. “Then, re-train new cordons or trunks as needed to maintain production.”

Also, be sure to remove diseased, woody debris from the vineyard and destroy it.

More information on controlling trunk diseases is available online at www.ipm.ucdavis.edu.