Among rootstocks commercially available with those qualities are Freedom and 1103 Paulsen.

Matthew Fidelibus, UC Davis extension specialist at UC Kearney Agricultural Center in Parlier, talked of canopy management in dried-on-the-vine vineyards.

He said it is important to prune so as to retain “sun canes” for better bud break rather than retaining shade canes. “Sunlight provides cluster initiation and development and bud survival,” Fidelibus said.

 

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He said that the Selma Pete variety is often planted on Freedom rootstock, which takes up less zinc, and he recommends applying zinc before bloom.

Larry Williams, UC plant pathologist at Kearney Ag Center, talked of nitrogen and potassium requirements of grapevines.

“Nitrogen can be stored and in the vine and can be redistributed,” Williams said, adding that post-harvest nitrogen applications are “not that beneficial.”

Williams said taking petiole and leaf samples to analyze nitrogen availability and use is important, particularly as regulatory controls are put into place on nitrates entering the groundwater supply.

Kent Daane, UC Cooperative Extension specialist at Kearney, discussed the raisin moth, which he termed a “garbage feeder” that thrives in settings where fruit is left to rot.

And he emphasized that fruit on a neighboring farm – perhaps figs or tree fruit – can be important to increasing infestations from the pest.

“The second or third flight periods of the moth are the key,” he said, advising against spraying for the pest in the first flight period when it is not expected to go after the grape in the early growth stages.

Instead, he said, the adults will leave, find another “garbage” source, then return.

He said dried on the vine grapes can risk more damage because ripening fruit is exposed to the moth for a longer time than are tray-dried grapes.

Karen Baumgartner, with ARS Davis, talked of grapevine trunk diseases and surveyed growers on the incidence of those problems and what they’re doing about it.

She recommends taking steps to avoid infection early – before symptoms are observed -- that can lead to esca, eutypa dieback, phomopsis dieback and brotryosphaeria dieback.

Those steps include delaying pruning until February and applying pruning-wound protectants.

She said older infected vineyards benefit little from those steps.

 

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