Weed Management Critical Needs for CA Processing Tomatoes

Amber Vinchesi-Vahl, UCCE — The Pest Management Strategic Plan for Processing Tomatoes in California (see attachment) was published in May 2021 and encompasses a wealth of information on pest issues and farming practices for processing tomatoes in California.

Myself, Cooperative Extension Specialist Cassandra Swett, and UC IPM collaborated on creating this document directly from stakeholder input and funding from the Western IPM Center. Below I have highlighted the documented critical needs for managing weeds in processing tomato production in California (more detail on each can be found in the PMSP, cited below). These needs were prioritized by growers, PCAs, academics and industry for the state, the northern growing region and the southern growing region and include research, regulatory and education priorities.

Statewide Critical Needs for Weeds


  1. Develop and identify management methods (including, but not limited to, herbicides) that work for difficult-to-control and perennial weeds, particularly nutsedge and field bindweed.
    1. Better understand weed biology and how to influence weed biology for the purposes of weed management, especially methods to break the dormancy of belowground structures (especially field bindweed and nutsedge).
  2. Develop effective, affordable methods to eradicate branched broomrape from processing tomato fields, prevent its spread, and manage infestations if it becomes well established in California (see Northern Region Critical Needs for Weeds for more information).
    1. Identify effective and practical sanitation methods, especially for eliminating broomrape seed on harvesting equipment (See Statewide General Critical Needs #3).
    2. Develop methods to detect branched broomrape and Egyptian broomrape in tomato fields more easily.” (p. 12).

Northern Region Critical Needs for Weeds


  1. Develop integrated weed management methods (including herbicides) for difficult weeds such as fleabane, horseweed, groundcherries, velvetleaf, nightshades, and glyphosate-resistant ryegrass and sunflowers.
  2. Conduct necessary efficacy research to register herbicides as described in the Northern Region Critical Needs for Weeds, Regulatory Needs.
  3. Identify environmental conditions and production practices that produce different weed problems, including soil quality and water management, and the efficacy of cultural practices to manage such weeds.
  4. Determine effective management practices for broomrape infestations.Research management practices (including herbicides) that control nightshades and reduce reliance on the costly practice of hand weeding.Research management practices (including herbicides) that control nightshades and reduce reliance on the costly practice of hand weeding.
    1. Determine the efficacy of methyl bromide alternatives (e.g., metam sodium/metam potassium, solarization, conventional herbicides).
    2. Identify biological control agents that may attack broomrape and test potential options.
    3. Determine or confirm how broomrape spreads from field to field, and ways to prevent its spread.
  5. Test efficacy of more postemergence herbicides (particularly those that can be sprayed over the top of the crop) and herbicides available for fallow bed weed control.


  1. Add or expand herbicide registrations.
    1. Register more fallow bed and preplant herbicides and increase application options (especially aerial and helicopter applications) to give growers weed control options to use in wet preplant conditions.
    2. Explicitly register herbicides for fallow bed management, not just preplant use.
    3. Identify and register herbicides that can be used near almond orchards.
    4. Register herbicides for difficult weeds such as fleabane, groundcherries, horseweed, nightshades, velvetleaf, and glyphosate-resistant ryegrass and sunflowers.
    5. Pursue 24(c) labels or Section 18 exemptions where necessary and possible.
    6. Register postemergence herbicides that are safe to apply over the top of the tomato crop to kill late-season weeds.


  1. Educate growers and pest control advisers on how to reduce herbicide drift. Many of the herbicides registered in processing tomato (e.g., carfentrazone) have drift issues.
  2. Conduct outreach to growers and pest control advisers about impacts of soil quality, water management, and other conditions that produce specific weed problems and how to avoid them via cultural practices.
  3. Educate growers and pest control advisers on how to reduce and manage glyphosate-resistant weeds (especially ryegrass, fleabane, and sunflower).” (p. 17).

Southern Region Critical Needs for Weeds


  1. Develop effective alternatives to glyphosate, especially those that are systemically translocated.
  2. Enhance cultivation methods for removing weeds, such as via finger and torsion weeders or robotic technology.
  3. Increase efforts to find effective biological control agents for weeds (e.g., research the effectiveness of the herbivorous mite that attacks Russian thistle).


  1. Register any effective and viable alternatives to glyphosate, especially systemically translocated herbicides.


  1. Educate growers on whether or how natural enemies can be used to manage Russian thistle and other relevant weeds.” (p. 17).

Weeds come up frequently in other areas of the PMSP, especially in relation to insect pest management.

You can also find descriptions of common weed problems on page 45 and weed management practices are included in the Farming and IPM Practices section starting on page 58. There is a weed occurrence table on page 75 in Appendix I, and efficacy tables for herbicides and nonchemical management starting on page 93 in Appendix II.

Martin, T., C. Swett, A. Vinchesi-Vahl, and S. Parreira. 2021. Pest Management Strategic Plan for California Processing Tomato Production. https://ipmdata.ipmcenters.org/documents/pmsps/2021_07_22_Processing_Tomato_PMSP_final.pdf

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