Invasive Weed Control Without Herbicides

Jul 14, 2021

Invasive Weed Control Without Herbicides

Jul 14, 2021

California has abundant wildlands — forests, rangeland, open areas, wildlife refuges and national, state, and local parks — that need protection from invasive plants. Invasive plants affect all Californians by increasing wildfire potential; reducing water resources; accelerating erosion and flooding; threatening wildlife; degrading range, crop and timberland; and diminishing outdoor recreation opportunities. According to the California Invasive Plant Council (Cal-IPC), more than 200 identified plant species harm California's wildlands.

Cal-IPC and the University of California Statewide Integrated Pest Management Program (UC IPM), with funding from the California Department of Pesticide Regulation (DPR) Alliance Grants Program, developed two resources that provide land managers access to the latest information on non-herbicide practices for managing weeds in wildlands. Best Management Practices for Non-Chemical Weed Control is a free downloadable manual. The same information has been incorporated into an interactive online tool called WeedCUT (Weed Control User Tool: weedcut.ipm.ucanr.edu).

"We anticipate WeedCUT will increase the use of more mechanical, physical, or biological practices, and potentially result in the reduction of herbicides used to manage wildland invasive weeds," said area IPM advisor emeritus Cheryl Wilen. "Best Management Practices for Non-Chemical Weed Control and WeedCUT were developed so land managers can become more knowledgeable and skilled in the use of non-herbicide methods as part of an IPM program.”

Knapweed control with a brush cutter. (Photo: Dawn Cunningham)

Best Management Practices for Non-Chemical Weed Control provides comprehensive descriptions of 21 commonly used non-herbicide weed control techniques and biological control agents for 18 invasive plants. Each chapter is the synthesis of research and on-the-ground knowledge from practitioners about non-herbicide methods. The chapters describe how a technique is best applied, the types of invasive plants and environmental conditions where it is most effective, and what its shortfalls might be. Environmental, cultural, and human safety risks are highlighted to help support the safe and effective use of these methods.

WeedCUT is the online version and can be used to learn about the different non-herbicide management methods, including the section on biological control. To filter through the database and learn which management practice to consider for a particular site and invasive plant type, a simple interface allows users to pick characteristics that describe their site and invasive plant problem. The tool then filters through the database to display the practices ranked by efficacy (excellent, good, fair, poor or ineffective). As in the manual, use of the technique and potential hazards are covered.

Best Management Practices for Non-Chemical Weed Control and WeedCUT are designed to be the go-to resources for practitioners that complement their conventional weed management work with non-herbicide techniques or are restricted in their use of herbicides. Both resources will help practitioners manage weeds more effectively.

Person releasing weevils for the biological control of Dalmatian toadflax. (Photo: Lincoln Smith USDA-ARS)

“Many experts in the field have contributed to create the manual and WeedCUT. It has been exciting to see these techniques described and reviewed so carefully. We're looking forward to seeing land managers, as well as all folks fighting weeds, incorporating the information from the manual and WeedCUT into their work,” said Jutta Burger, science program director and project lead with Cal-IPC.

While the manual and tool focus on non-herbicide methods, the hope is future funding can be found to continue the work and integrate herbicide options online.

"Land managers typically use both herbicide and non-herbicide methods, alone and in combination, to manage invasive plants in wildlands," said UC Cooperative Extension advisor and UC IPM-affiliated advisor Tom Getts. "A tool that combined both herbicide and non-herbicide methods would guide land managers to determine the most effective overall management program for their particular site." 

Yellow starthistle is an invasive rangeland weed. (Photo: J. M. DiTomaso)