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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 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?

Herbicides are presently the most successful method for leafy spurge control, but are costly and have limited use in many environmentally sensitive areas, such as riparian zones, wetlands, woodlands, and rough terrain. Biocontrol of leafy spurge using insects could reduce herbicide use and costs associated with application and may control leafy spurge in environmentally sensitive areas.

Question 3: How does it relate to the National Program(s) and National Program Component(s) to which it has been assigned?

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 were the most significant accomplishments this past year?

Two significant accomplishments in 1999 were soil sampling of 60 biocontrol release sites and soil seed bank analysis of long-term leafy spurge infestations. Soils at release sites were cored, refrigerated, and shipped to a soil testing laboratory where physical and chemical analysis will be conducted. This information will be used to examine ecological barriers to insect biocontrol establishment and population movements. The soil seed bank analysis will evaluate the natural revegetation potential of leafy spurge infested sites once leafy spurge densities have been reduced.

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

A total of 141 permanently located research sites, 99 insect release, and 42 controls were established in 1998. Complete physical, biological, and cultural inventories of sites were made. Research sites included summit/backslope, toeslope, and riparian topographic positions, shallow and silty range sites, steep (30% slope) sites, and various aspects. Insect establishment and population growth will be expected to reduce leafy spurge densities at many of the original release sites. The biological and physical data collected at release sites should allow a better understanding of habitat requirements of insect biocontrol agents.

Question 6: What do you expect to accomplish, year by year, over the next 3 years?

Over the next three years we expect to: 1) determine the best methodology for utilizing the COAST digital imaging system for sampling leafy spurge and herbaceous ground cover, 2) map and ground truth leafy spurge infestations on the 10 km X 10 km (36 section) study area, 3) analyze long-term leafy spurge infested sites for their soil seed banks, and 4) evaluate insect biocontrol of leafy spurge and correlate biological and physical data with success of biocontrol.

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 products?

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.

Question 8: List your most important publications in the popular press and presentations to non-scientific organizations and articles written about your work.

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.

Question 9: Scientific Publications
None to date.
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