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Ecological Assessment of Leafy Spurge in the Little Missouri River Drainage

 Don Kirby

Question 1. What major problem or issue is being resolved and how are you resolving it?

Leafy spurge, an introduced plant, occupies approximately 400,000 hectares of rangeland in North Dakota resulting in an estimated reduction in direct net annual income of $23 million from livestock sales. Herbicides have been the most successful control program to date, but treatment costs often exceed the total land value and approximately eight to 10 times the annual cash rent value of the land. Biocontrol of leafy spurge using insects has expanded over the past decade, but has had limited success due to a lack of insect species and the little knowledge of insect biology and habitat requirements for establishment and population growth. A greater understanding of insect establishment protocol and habitat requirements will improve the success of insect biocontrol efforts for controlling leafy spurge.

Question 2. How serious is the problem? Why does it matter?

Leafy spurge occupies nearly 9% of North Dakota's rangelands and without management will quickly spread across the state. The introduced, perennial species is highly competitive and will displace many native species. The ecological effects of leafy spurge invasion into rangeland have been decreased plant diversity, increased potential for soil erosion, and degraded wildlife and recreational habitats. Economically, leafy spurge reduces forage production for the livestock industry, thus decreasing land values also.

Question 3. How does it relate to the National Program(s) and National Program Component(s)?

The TEAM Leafy Spurge project is a part of the USDA/ARS Area-Wide Management Program. It is a component of Crop and Commodity Pest Biology, Control and Quarantine (304). TEAM Leafy Spurge complements efforts to develop new and improved pest control technologies and assess component technologies for integrated pest management (IPM) systems.

Question 4. What was your most significant accomplishment this past year?

Leafy spurge, an introduced plant, occupies approximately 400,000 hectares of rangeland in North Dakota resulting in an estimated reduction in direct net annual income of $23 million from livestock sales. In 1998, 101 insect biocontrol sites and 43 control sites were established in leafy spurge infestations in the Little Missouri River drainage of western North Dakota and are being monitored annually. Two range sites, silty and overflow, will be evaluated for plant species composition, diversity, richness, and density, cover and production of herbaceous plants colonizing the sites. The major transfer of technology to date has been a better understanding of the habitat requirements for optimum establishment and success of insect biocontrol agents.

Question 5. Describe your major accomplishments over the life of the project, including their predicted or actual impact.

In 1998, 101 insect biocontrol sites and 43 control sites were established in leafy spurge infestations in the Little Missouri River drainage of western North Dakota. A total of 6,000 black and brown flea beetles (Aphthona spp.) Were released at each site. Sites varied by aspect, topoposition, topography, and soils. Leafy spurge reductions have been phenomenal in only two years. Of 98 remaining insect release sites, 85% have had good (> 400 m2) leafy spurge control, while only 5% have shown poor (< 200 m2) control of leafy spurge. Leafy spurge canopy cover at release points has decreased from approximately 40% to less than 5% over the two growing seasons. Leafy spurge control has been similar across aspect (N, S, E, W), soil (silty, sandy, clayey), range site (silty, overflow) and topography (steep > 30° slope to flat).

Question 6. What do you expect to accomplish year by year, over the next three years?

Leafy spurge cover and density will continue to be monitored to the termination of the study. A phytosociological study of leafy spurge sites will begin in 2001. Two range sites, silty and overflow, will be evaluated for plant species composition, diversity, richness, and density, cover and production of herbaceous plants colonizing the sites. These data will be collected on similar range sites having no leafy spurge control, leafy spurge controlled and never infested sites.

Question 7. What science and/or technologies have been transferred and to whom? When is the science and/or technology likely to become available to the end user (industry, farmer, other scientists)? What are the constraints, if known, to the adoption and durability of the technology?

The major transfer of technology to date has been a better understanding of the habitat requirements for optimum establishment and success of insect biocontrol agents. This has been transferred by demonstration and in presentations to ranchers, technicians, and researchers in the field and at meetings, including Spurgefest I.

Question 8. List your most important publications in the popular press (no abstracts) and presentations to non-scientific organizations, and articles written about your work (NOTE: this does not replace your peer-reviewed publications which are listed below).

The results of this research effort have been written up in numerous newspaper, farm journal, and agricultural extension reports over the past two years. It also was presented at the 1999 Leafy Spurge Symposium held in Medora, North Dakota (see Proceeding: 1999 Leafy Spurge Symposium).

Question 9. Scientific publications

Kirby, Don, Mark Mayek, Dean Cline, Kelly Krabbenhoft and Connie O'Brien. 1999. Site characteristics of established flea beetle colonies in western North Dakota. Proc. 1999 Leafy Spurge Symposium, Medora, ND.

Cline, Dean, Donald Kirby, Kelly Krabbenhoft, and Gerald Anderson. 2001. 2001. Relationship of seedbank composition and leafy spurge density. Abstr. 54th Annual Meeting, Society for Range Management, Kona, Hawaii.

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