Invasive plants are a key challenge for land managers of natural areas. Invasive plants disrupt natural ecosystems, often causing substantial changes to the invaded habitat. Invasive plants cause economic loss by reducing livestock forage quality and quantity, harming animal and human health, increasing the threat of fire or flooding, interfering with recreational activities, or lowering land value. The California Invasive Plant Council (Cal-IPC), a nonprofit organization, lists over 200 invasive plants that harm wildlands in California. Controlling invasive plants is part of the mission of many land management entities, such as state and federal agencies, local utility districts, park districts, and land conservancies.

While herbicides are frequently used to manage invasive plants in natural areas, there is increased public pressure to reduce herbicide use. With input from an external natural resources committee, Natural Resources IPM Coordinator Cheryl Wilen developed a survey about the use of nonherbicide weed management methods in natural areas. In cooperation with state and regional land managers, Cal-IPC staff, and state and regional park agencies, the survey was distributed statewide. Results were reported at the statewide annual Cal-IPC Symposium.

Wilen received 138 responses. The respondents had a range of roles as field workers, project coordinators, or project leads. Locations also varied covering invasive plant management in coastal, riparian, grassland, forest, rangeland, woodland, chaparral, aquatic, and desert areas. Most were responsible for covering over 100 to 10,000 acres. The top invasive plant management goals for the respondents were to maintain or improve native plant cover and diversity, maintain or improve wildlife habitat, and maintain or improve public access or experience. Many respondents agreed that multiple practices improved invasive plant control. The following is a partial list of responses to whether land managers integrated weed management practices and why:

• Yes! Often combined treatments get the job done. This is all species and site specific. One example is a Cape ivy spray after flowering. After the product has had months to work (necessary when using aminopyralid), it is helpful to go through and do hand follow up on the plants that did not fully die back.
• Yes. Control is dramatically improved if chemical follows manual cutting as for pampas grass and site preparation for restoration planting where herbicide application can follow mowing. Conversely, we frequently do a chemical control early on and follow it up with focused hand weeding.
• Yes. Chemical control that follows weed trimming or burning has been effective on lands not controlled by my previous work.

The results of the survey were used as the basis for a successful California Department of Pesticide Regulation (DPR) Pest Management Alliance Grants Program proposal. DPR’s Pest Management Alliance Grants Program funds projects by a team of individuals representing state, local, public, private, educational, and other stakeholders that increase the use of integrated pest management. The Pest Management Alliance Grants project is developing a decision support tool—putting in one place the science-based information on nonherbicide management. Using this decision support tool land managers, governance boards, and residents are informed about the effectiveness of nonherbicide management practices and can make educated decisions on using them.

Surveying invasive plant managers showed that many use nonherbicide management tools and practices. This increase in knowledge about what nonherbicide pest management tools or practices are used will ensure the online decision support tool will be practical and useful for making decisions that best manage invasive plants.  

Long-Term Impacts

• Improved management and use of land
• Increased ecological sustainability of natural areas
• Decrease in environmental problems caused by pests or pest management, such as improved air and water quality
• Human health risks from pests and managing pests are reduced, leading to improved community health and wellness
• Improved access to natural environments