Sonoma County wine grape growers with larger acreages finished mechanical pre-pruning activities earlier last month, says Nicky Frey, president of the Sonoma County Wine Grape Commission at Santa Rosa, Calif.
Pre-pruning is done to reduce Eutypa dieback — caused when spores of the fungus infect fresh pruning wounds — by reducing the chance of rain spreading the spores. It is done more by machine than by hand in Sonoma County, speeding up the final selective pruning and allowing growers to prune large acreages in a very short time.
Growers have been non-selectively cutting canes to about 15 to 18 inches since November or December. Now, they’re doing the final selective pruning, cutting back to two-bud spurs on cordon-pruned vines.
Other growers, typically those with smaller operations, have been waiting to begin pruning until the apical buds begin to swell or even emerge.
“Pruning now tends to delay basal buds from pushing out for a week or two and reduces the risk of frost damage,” Frey says. “We’ve had excellent rains this winter and the soil profiles are fully charged. That’s always good going into a new season. Hopefully, we got good dormancy that will set us up pretty well for this spring so bud break occurs over a shorter period.’
Growers have begun setting out traps for the European Grape Vine Moth (EGVM), an invasive pest discovered for the first time in the U.S. two years ago in a Napa County vineyard.
Frey is encouraged by the low number of EGVM moths trapped last year — a total of just 53 in all three flights.
“If treatments were effective, there may be some areas where we won’t find the pest this year. We’ll see, but I remain optimistic that we can eradicate this pest from our county.”
Last year’s unusually cool growing season, interrupted by a few days of 100-degree plus temperatures in August, challenged the skills of even Sonoma County’s best growers. This year, they’re looking for a more normal season for producing wine grapes.
“Nothing suggests anything unusual this year,” Frey says. “At this stage, growers should be expecting an average crop.”