California Pepper Commission


Proposal Smith 15Pepper Commission Weed Control PROPOSAL 2015

California Pepper Commission - Research Proposal, 2015 Title: Preemergence Weed Control Trials in Peppers

Principle Investigators:

Richard Smith

Farm Advisor, Monterey County 1432 Abbott Street

Salinas, CA 93901

(831) 759-7350; (831) 758-3018 FAX

Timeline: March 1, 2015 to February 28, 2016


Peppers are long-season vegetables that have a several effective registered herbicides; however, there are gaps that remain in the spectrum of key weeds controlled by currently registered herbicides (Smith et al., 2008). As a result, growers may spend significant amounts of money, especially later in the season, to control weeds in peppers. Peppers have a good array of weed control materials available to enable growers to be able to control many problematic weeds. However, given the long growth cycle for peppers, late season weed control continues to be a problem on pepper grown without plastic mulch. Our efforts over the past few years have been to evaluate herbicides and combinations of herbicides to provide late-season weed control.

In 2013 and 2014 we observed that Zeus (FMC Corporation) showed promise as both a pre-transplant. This material has potential for at least partially controlling malva and we would like to evaluate rates to effectively control this weed. It also has some preemergent activity on yellow nutsedge. K-I USA/Kumiai has a new preemergent herbicide, pyroxasulfone, that is in the same chemical family as Dual Magnum. They are interested in testing it on vegetable crops in California. There have not been many new chemicals available for testing for use on peppers and we will include it in these trials.

Table 1. Proposed weed control treatments

No. Pre-transplant Application Lbs a.i./A
1 Untreated --- ---
2 Dual Magnum (standard) pretransplant 1.43
3 Zeus 4F pretransplant 0.094
4 Zeus 4F pretransplant 0.188
5 Pyroxasulfone pretransplant 0.13
6 Pyroxasulfone pretransplant 0.20


1) Examine pre-transplant use Zeus and Pyroxasulfone for early and late season weed control.


Weed control trials will be established in Monterey County. Pretransplant applications will be made before transplanting. Crop safety, weed control, yield and quality evaluations of the peppers will be conducted.

Literature Cited

California Pesticide Impact Assessment Program (CPIAP). 2000. Crop Profile for Bell Peppers.

Smith, R. F, O. Daugovish, C. Bell and T. Lanini. 2008. Pepper Pest Management Guidelines - Weeds. University of California Integrated Pest Management Program. Available on line at:


I. Budget

  1. Salaries Field Assistant
    (30% time, 4 months) $3,500
  2. Travel
    (200 miles/week for 14 weeks @ $0.51/mile) $1,500
  3. Subtotals
    Monterey County $5,000

  4. Total $5,000


Richard Smith
Principal Investigator

Maria De La Fuente
Monterey County Director

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