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SAFETY AND EFFICACY OF HERBICIDES IN BEARING AVOCADO GROVES IN SOUTHERN CALIFORNIA

Applied Research

Sonia Rios
Area Subtropical Horticulture Advisor
University of California Coop. Ext.
Moreno Valley

Abstract

 


Currently there are only 10 herbicide active ingredient (a.i.) groups registered for use on bearing avocado (Persea americana Mill.) groves in California. Of these, paraquat is a restricted use herbicide and glyphosate is under increasing political scrutiny. Another consequence for lack of a.i. is the chance of increasing herbicide tolerant or resistant weed biotypes. The purpose of this study was to see if we could provide more chemical options for avocado growers. A study to evaluate phytotoxicity and efficacy of pre- and postemergent herbicides that are currently registered in California citrus. Herbicides applied in fall or spring were evaluated on bearing avocado trees in Riverside, CA. The experiment was a replicated complete block design with four replications. Treatments included: caprylic/capric acid, clethodim, flumioxazin, glufosinate, glyphosate, indaziflam, isoxaben, oxyfluorfen, pendimethalin, rimsulfuron, salfufenacil, simazine, s-metolachlor, and an untreated control.  Herbicide applications were made using a calibrated CO2 backpack sprayer. Following treatment applications, the pre-emergence herbicides were incorporated using temporary sprinkler systems to simulate 0.5 inch of rainfall. Weeds were 2-4 inches tall at the time of application. The primary weeds in the plots were tumble pigweed, common purslane, sow thistle, little mallow, and burning nettle. Although not a predominant weed hairy fleabane was also found sporadically throughout the orchard. Weed mortality and phytotoxicity were monitored at 1, 2, 4, and 8 weeks after treatment (WAT) during both seasons. First year’s data from this study indicated that preemergents indaziflam and rimsulfuron have good potential for weed control in bearing avocado with very little to no phytotoxicity. Similarly, glyphosate and glufosinate, both postemergents, also provided excellent control, however, can have phytotoxicity concerns. We continued this project in fall 2020 and will spraying the last application in spring 2021. Preliminary results for this 2-year study look promising.

Poster has NOT been presented at any previous NACAA AM/PIC

This poster is being submitted for judging. It will be displayed at the AM/PIC if not selected as a State winner. The abstract will be published in the proceedings.

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Authors: S. I. Rios, P. Mauk, B. Faber, O. Daugovish, T. Bean, D. Vega, G. Ferrari
  1. Rios, S. Area Subtropical Horticulture Advisor, University of California Cooperative Extension, Riverside and San Diego Counties, California, 92557-8718
  2. Mauk, P. Subtropical Horticulture CE Specialist, University of California, Riverside, Department of Botany and Plant Sciences, California, 92521
  3. Faber, B. Subtropical Horticulture CE Farm Advisor, University of California Cooperative Extension, Ventura County, California, 93003
  4. Daugovish, O. CE Farm Advisor, University of California Cooperative Extension, Ventura County, California, 93003
  5. Bean, T. Weed CE Specialist, University of California, Riverside, Department of Botany and Plant Sciences, California, 92584-7119
  6. Vega, D. Staff Research Associate, University of California Cooperative Extension, Ventura County, California, 92584
  7. Ferrari, G. Lab Assistant, University of California Cooperative Extension, Ventura County, California, 92584