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Napa County UCCE
University of California
Napa County UCCE

Weed Science

Program Focus

Weed control and identification
Vegetation management
Covercrop information

Timing of herbicide applications
Effect of leaf litter on the efficacy of treatments
New organic herbicides with organic growers



If you have a question or a concern related to weed management, vineyard or orchard floor management, or need assistance in the identification of a weed species, please call or e-mail me. 

UC Master Gardeners of Napa County are available to assist homeowners with weed questions.


Photo of John A Roncoroni John A Roncoroni
Title: Weed Science Farm Advisor
Specialty: Weed Control and Vegetation Management in Perennial Crops, Covercrops and Aquatic Weed Control
UC Cooperative Extension
1710 Soscol Avenue
Suite 4
Napa, CA 94559-1315
Phone: (707) 253-4221


Wines & Vines Article - 7/22/14

UC Weed Science Farm Advisor, John Roncoroni details results of vineyard studies in the current issue of Wines & Vines.  Read the article,  "The Efficacy of Weed Killers" written by Paul Franson.  For additional information contact John Roncoroni at

Update - Latest Field Ratings

Read the details of field trial - plots were treated on February 5, 2014.

Read the update on the latest field ratings.

2013 Weed Control Trial

Read the test results of a 22-treatment herbicide weed control trial conducted in Napa County in 2013.

New Weed Management Book

Order now!
Order now! - Weed Control in Natural Areas in the Western United States

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