Integration of Biological Control and Native Cover Crops for Canada Thistle Control

View the project final report

Commodities

• Additional Plants: native plants

Practices

• Crop Production: cover crops
• Pest Management: biological control, integrated pest management, weed ecology
• Production Systems: agroecosystems, organic agriculture

Canada thistle (Cirsium arvense) is an invasive weed in many croplands, rangelands, and natural areas. It is a noxious weed in 43 states, and has infested over one million acres in North Dakota. Infestations displace native plants, reduce crop yields, and affect ecosystem nutrient, water, and energy cycles. Effectively managing Canada thistle is challenging, and using individual control tactics (such as herbicides, tillage, and mowing) has only been moderately successful. Additionally, Canada thistle is a particularly difficult challenge for organic and sustainable producers who wish to limit chemical inputs and for land managers who need to control Canada thistle in environmentally-sensitive areas where herbicide use may either be prohibited or cause contamination. Therefore, an integrated pest management (IPM) program incorporating multiple control tactics may be helpful to more effectively and sustainably manage Canada thistle infestations. The proposed research will use an integrated approach to controlling Canada thistle by investigating the combined impacts of a biological control agent (Hadroplontus litura Fabricius, a stem-mining weevil), and a native cover crop (Helianthus annuus L., common sunflower). Biological control is an environmentally friendly, self-sustaining pest control tactic, and establishing native vegetation to compete with Canada thistle may additively or synergistically enhance the efficacy of biocontrol agents. The ultimate goal and outcome of this research is to provide farmers, ranchers, and land managers with sustainable, effective methods for Canada thistle control that will lead to increased crop yields, improved pasture/rangeland quality, and enhanced agroecosystem health. Results from this project will be disseminated regionally using presentations at Thistle Day workshops and nationally via presentations at scientific conferences and peer-reviewed publications.

Project Outcomes:

Short-Term Outcomes: The integrated pest management (IPM) of Canada thistle project will substantially impact the noxious weed control knowledge of farmers, ranchers, and land managers (hereafter referred to as stakeholders) currently struggling with sustainable Canada thistle control in the Northern Great Plains. Knowledge gained from this research will expand interest in non-chemical alternative methods for controlling Canada thistle and will provide information about how stakeholders might improve their operations by deploying integrated, environmentally sound strategies. This project will be the initial step in investigating the efficacy of self-sustaining agroecosystem-friendly approaches for controlling Canada thistle.
Intermediate Outcomes: This project will demonstrate the effects of combining biological control, cover crop competition, and soil nutrients for Canada thistle suppression. This research will evaluate each management tactic alone and in combination to discover the most effective control method. The proposed research will provide stakeholders with concrete data about direct effects this integrated sustainable approach has on Canada thistle. Such information is currently lacking and often recommendations for sustainable control methods are frequently based on anecdotal observations, but seldom on research results. The proposed research will provide an alternative method of weed control for environmentally conscious producers in the region and will increase profits by lowering the cost of Canada thistle management and increasing revenues by restoring land that was previously unusable due to heavy thistle infestations.
Long-Term Outcomes: The long-term goal of this project is to demonstrate the utility and potential of integrated weed control approaches, including, but not limited to, the methods investigated by the proposed project. Unlike many noxious and invasive non-native weeds, Canada thistle is also a substantial problem in its native range of Eurasia. Therefore, not only would stakeholders in the Northern Great Plains be positively impacted by this research, but land managers throughout the world where Canada thistle is found could benefit. The success of the proposed research has the potential to spur systemic changes in sustainable approaches to managing Canada thistle and invasive weeds in general.

Evaluation Plan: Evaluation of process indicators will occur weekly via plant measurements and observations of weevil activity. Evaluation of experimental outcome indicators will occur at the end of the experiment, when above and below ground plant biomass will be collected from microcosms. Evaluation of stakeholder impact outcome indictors will be determined via questionnaires designed to determine Thistle Day workshop participant awareness, interest, and view of feasibility of the integrated Canada thistle control measures.