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Field Investigation Assessing the Impact of Area-Wide Biological Control Agents on Non-Target, Native Euphorbia species

 Jack Butler

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

Leafy spurge (Euphorbia esula L.) is an exotic plant species accidentally introduced into North America in the late 1800's. Leafy spurge is now well established throughout much of the Northern Great Plains. Much of the current research emphasizes conventional and integrated control programs utilizing herbicides, biological insect control, and behaviorally encouraging lambs and goats to preferentially graze on leafy spurge. However, little information that specifically addresses the possible impacts of biological control on non-target native Euphorbia species is available. The objective of this study is to document the effects of two species of flea beetles (Aphthona nigriscutis and A. lacertosa) on non-target Euphorbia species (see list below). A preliminary list of non-target species that could potentially occur within the TEAM Leafy Spurge project area, which includes North Dakota, South Dakota, Wyoming, and Montana, was developed using information provided by Pemberton (1984). According to Pemberton (1984) the following species may occur in the project area and should be considered when evaluating the effects of biological control on non-target species: Euphorbia corollata (perennial), E. cyathophora (annual), E. dentata (annual), E. fenleri (perennial), E. greyeri (annual), E. glyptosperma (annual), E. heterophylla (annual), E. maculata (annual), E. marginata (annual), E. robusta (perennial), E. serpens (annual), E. spathulata (annual), and E. stictospora (annual).

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

Leafy spurge is now well established throughout much of the Northern Great Plains. Heavy infestations of leafy spurge dominate and displace many native plant species. Lym and Messersmith (1987) reported that leafy spurge infestations can reduced carrying capacity for livestock by 50-75%, with much of this loss attributed to decreased forage production and avoidance of infested sites (Lym and Kirby 1987, Hein and Miller 1992). Similar reductions in habitat use by native ungulates on leafy spurge infested sites were reported by Trammell and Butler (1995) for Theodore Roosevelt National Park, North Dakota. Biological control agents such as flea beetles (Aphthona sp.) are receiving widespread attention in their ability to effectively reduce the cover and density of leafy spurge in certain situations. However, very little information is available that specifically addresses the potential impact such biological control may have on non-target, native Euphorbia sp. under field conditions. Such information is essential to the development of a comprehensive integrated pest management plan on a regional level (i.e. TEAM Leafy Spurge).

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?

To document the effects of two species of flea beetles (Aphthona nigriscutis and A. lacertosa) on non-target Euphorbia species. The herbariums at South Dakota State University, University of South Dakota, Black Hills State University, North Dakota State University, and the University of Wyoming were visited during the 2000 field season. Extensive field surveys were conducted in the North Dakota, South Dakota, Wyoming, and Montana project areas, as well as several sites outside the project area (Lander, Wyoming and Wind Cave National Park, South Dakota). This information will provide valuable insight as to the overall effects of biological control agents on biodiversity at the local, landscape, and regional levels.

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

The major accomplishments so far indicate that Native Euphorbia species are difficult to locate and, when found, tend to occur infrequently and at low densities. Upon expected completion of the project in May 2003, the predicted impact will include a synthesis of the actual and potential impact of biological control on non-target native Euphorbia species. This information will provide valuable insight as to the overall effects of biological control agents on biodiversity at the local, landscape, and regional levels.

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

Specific study sites are expected to be established and monitored during the 2001 field season. Sites established during the 2001 field season will be monitored during the 2002 field season, and a final report detailing the results of the experiment should be available by May 2003.

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 project has just started and only preliminary information is available; consequently, no opportunities for technology transfer have been available. The end product should be available to land managers during the summer of 2003. The major constraint will involve finding sufficient study sites to rigorously evaluate the project objective.

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).

None.

Question 9. Scientific publications

None.

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