Grape Weed Control Benefits New and Established Vines

Matrix® SG helps control grape weeds to keep vineyards clean.

Each season poses different challenges when it comes to grape weed control in California vineyards. This year brought wet conditions early in the year for the North Coast region, which prevented timely early-season grape weed control applications and allowed weeds to flourish.

“It was a tough year for grape weed control in our area,” says John Roncoroni, weed science farm advisor, University of California Cooperative Extension, Napa County. “Rain kept growers from preventing an early crop of weeds. And by the time herbicide applications could be made, the rain stopped and we didn’t get the moisture necessary for incorporation.”

Roncoroni notes that uncontrolled weeds can undermine young vine growth and overall grape production.

“Weeds are a big competitor for water, nutrients and sunlight with young grapes. Then after grapes are established, weeds cause a different set of problems,” he explains. “In established vineyards, grape weeds can impede valuable irrigation in the drip zone, provide habitat for damaging mice and voles, and hamper harvest.”

Tips for Keeping Beds Clean

To avoid these production limitations, grape weed control should be part of a long-term vineyard management program, Roncoroni notes. He recommends the following steps for keeping grape weeds under control and beds clean.

  • Select the best control options. Both preemergence and postemergence grape weed-control strategies may be needed to manage particular weed populations.
  • Control late-season weeds promptly. Apply a contact herbicide as soon as possible after harvest to control weeds that have germinated in late summer or early fall.
  • Apply a preemergence herbicide just before bud break in the spring. For best control, make applications to clean beds when rain is expected within three weeks. This helps incorporate herbicide into the soil for optimum control.
  • Rotate herbicides. Use herbicides with different modes of action to avoid herbicide resistance development, considering use for preemergence, postemergence or both.
  • Employ cultivation. When landscapes allow, add cultivation to the rotation every few years, especially before planting vines.

Long-Lasting Preemergence Control

An effective grape weed-control option for growers is DuPont™ Matrix® SG herbicide. Applied preemergence, Matrix® SG helps keep vineyard beds clean long into the season. As part of an integrated grape weed management plan, Matrix® SG helps minimize weed seed banks and control tough problem weeds, including glyphosate-resistant marestail (horseweed) and hairy fleabane, plus common mallow and yellow nutsedge (partial control).

In commercial applications, PCAs and growers have observed 120 or more days of preemergence soil residual control for hairy fleabane and marestail with Matrix® SG.

Roncoroni has included Matrix® SG in his trials for several years and reports it provided very good grape weed control when the test plots received the necessary rain after application.

“I applied Matrix® SG on January 9 this year and received just enough rain to incorporate it after application,” Roncoroni says. “The conditions were just right to achieve good weed control. On July 17, some of the Matrix® SG plots were still looking good.”

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