Leafy Spurge Project

SUMMARY

The Leafy Spurge Project was initiated by The Nature Conservancy (TNC) in cooperation with the University of North Dakota, Fargo. Beginning in 2000, a field experiment has been conducted, examining: 1) the impacts of spurge infestations on native plant communities; and 2) the response of spurge to biological control by flea beetles (Apthona spp.).

Ecological Strategies was contracted to collect field data in 2003 and to analyze the first three years of data. Data analysis is underway.

Prairie landscape at Broken Kettle, near Sioux City, Iowa
Prairie landscape at Broken Kettle, near Sioux City, Iowa

Liatris aspera and Psoralea argophylla at
Liatris aspera and Psoralea
argophylla at Crystal Springs
Preserve, Clear Lake SD.

INTRODUCTION

Leafy spurge (Euphorbia esula) is one of the most detrimental noxious weeds threatening grassland ecosystems. On several grassland preserves, TNC recently began employing biocontrol of leafy spurge by flea beetles (Apthona spp.). This study examines the impacts of spurge infestations on native plant communities and the response of spurge to biological control by flea beetles (Apthona spp). Sampling plots were located at four sites: Audubon Preserve, near Dilworth, Minnesota; Broken Kettle Preserve, near Sioux City, Iowa; Brown Ranch in Milnor, ND; and Crystal Springs Preserve near Clear Lake, SD.

METHODS

A total of forty permanent circular plots were established at the four sampling sites. Thirty-five plots were established in spurge patches with no history of flea beetle activity prior to the release of beetles at the plot during the first sampling season. At one site, five plots were established as paired plots, and were located in areas where no leafy spurge was present, and which had similar abiotic features (soil type, slope, aspect) as sampling plots. Additional paired plots have been identified at other sites, but have not yet been sampled. Within each circular plot (10m diameter), 18 quadrats (.5 m x .2 m) were located along 6 radii of the plot. Each quadrat was sampled for: 1) an inventory of all plant species present and; 2) stem counts of leafy spurge. In the five paired plots, all plant species present were inventoried. In 2001 and 2002, most plots were sampled twice during the growing season. During 2003, all plots were only sampled once, during July or August.

RESULTS

Results are being compiled, and statistical analyses are beginning. Leafy spurge stem counts will be used to document the changes in leafy spurge abundance in the years following beetle release. The plant species presence and frequency data will be used to determine if native species are responding to any changes in leafy spurge abundance as a result of flea beetle herbivory.

Contact person: Cynthia Lane and Carolyn Carr, Ecological Strategies. Project partners include: The Nature Conservancy and the University of North Dakota. Funds for this project were provided by The Nature Conservancy (RJKOSE Stewardship Fund).