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Assessing Biological Control Agents for Area-Wide Integrated Pest Management (IPM) of Leafy Spurge with foci in Montana and South Dakota

 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 that was accidentally introduced into North America in the late 1800's. Much of the current research emphasizes conventional and integrated control programs utilizing herbicides, biological insect control (Gagne, 1990, Gassman and Shorthouse, 1990, Pecora et al., 1989), and behaviorally encouraging lambs and goats to preferentially graze the weed (Walker et al., 1992). The success of this exotic weed species is due in part to its ability of tolerate and exploit a variety of habitats and environmental conditions (Morrow, 1979). The objective of this study is to document the micro-scale distribution, density, dynamics and trends of leafy spurge populations in response to flea beetle control within the Montana and South Dakota study areas. Sites specifically selected for detailed study represent the wide range of topographic, soil, vegetation, and landform situations typical of the regions.

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 used by native ungulates on leafy spurge infested sites were reported by Trammell and Butler (1995) for Theodore Roosevelt National Park, North Dakota.

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 (Euphorbia esula) is an exotic perennial weed that infests over 5 million acres of grazing lands and wildlands in at least 35 states. We are documenting the micro-scale distribution, density, dynamics and trends of leafy spurge populations in response to flea beetle control within Montana and South Dakota study areas. Plant species composition and cover, and flea beetle abundance were evaluated during the 2000 field season for all selected sample sites in Montana and South Dakota. 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.

At total of 93 permanent sample sites (60 flea beetle release sites and 33 control sites) were established within the Montana and South Dakota portions of the TEAM Leafy Spurge project area. Approximately 6,000 beetles (3,000 Apthona lacertosa and A. nigriscutis) were released in June 1998 at each of the 60 release sites. Abundance and composition of flea beetles were evaluated during the 1999 and 2000 field seasons. Plant species composition and density and cover of leafy spurge in relation to biological control by flea beetles were evaluated on all sample sites. The expected output of this project will include an analysis of the efficacy of flea beetle control under a wide variety of physical and biological conditions in western South Dakota and eastern Montana. This will include recommendations for the selection of release sites that have the greatest potential of effecting control of leafy spurge both in terms of the extant infestation and the soil seed bank. Detailed descriptions of specific sites that have the lowest potential of control, either because of reduced establishment of flea beetles and/or persistent seed bank, will also be included. These recommendations could possibly be presented in a simple dichotomous key that could be used by land managers/owners in selecting release sites. This document could easily be integrated with the results from the other Ecological Assessment teams in Wyoming and North Dakota producing an area-wide management plan. This information should be available to the end user at the conclusion of the ecological assessment portion of TEAM Leafy Spurge (May 2002).

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

We expect to continue monitoring the establishment and persistence of flea beetles on both release and control sites during each year of the next three years. The recovery of native and forage vegetation following control of leafy spurge will be carefully monitored and evaluated every year for the next three years. In addition, soil seed bank analysis will be conducted using the described protocol in October 2001 and compared to the initial 1998 data. Range site descriptions will be prepared in 2000 and 2001 and used to determine potential plant communities for the Montana and South Dakota Study Areas. Existing plant communities will be evaluated from a series of randomly selected points within each range site. The goal is not to evaluate range condition of non-infested sites, but rather to compare species composition between infested and non-infested areas within each range site. A major goal for the 2000-2002 portion of this project is to compile all of the physical and biological information collected over the four-year study period into a geographic information system (PC ArcView).

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?

My research crew and I have participated in several demonstration trials for area land managers (private and public)at our study sites in Montana and South Dakota. Further, I actively participated in SPURGEFEST and in the Annual Leafy Spurge Symposium in 1999. Integrated pest management has become a major topic in several of the courses that I teach at CMSU. The TEAM Leafy Spurge concept has been a major theme in those presentations. The end product should be available to land managers during the summer of 2002. I do not anticipate any constraints at this time.

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).

Assessment of biological control agents for area-wide integrated pest management of leafy spurge in Montana and South Dakota. M.S. Parker and J.L. Butler. Paper presented at the 2000 Annual Meeting of the Missouri Academy of Science, April 14-15, 2000, Columbia, Missouri.

Question 9. Scientific publications

None.

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