PARENT SESSION
Poster Session #4: Invasions.
Monday, August 6, 2001. Presentation from 10:30 AM to 12:00 PM. Exhibition Hall

Experimental treatment for Euphorbia esula infestations at Arrowwood National Wildlife Refuge.

LARSON, JENNIFER¹, LARSON, DIANE¹, ¹

ABSTRACT- Methods of weed control may include top-down (biological control) and bottom-up (plant community and nutrient manipulation) procedures. In an ongoing study, we combine these procedures to manage the exotic invasive species Euphorbia esula. Since 1991, the biocontrol flea beetles Aphthona nigriscutis, A. czwalinae, and A. lacertosa have been released throughout Arrowwood National Wildlife Refuge, ND, the location of our study sites. Prior to the interseeding of native grass species and nutrient manipulation in spring 2001, we collected data (E. esula and biocontrol abundance, plant biomass, species composition, and soil nitrogen) for several sites within two study areas (AW and GH) at the refuge that differ in existing plant communities. The change in number of E. esula stems between 1998 and 2000 at AW was best explained by 1999 A. nigriscutis abundance, 1998 E. esula stem counts, 2000 A. czwalinae/A. lacertosa abundance, and biomass of non-native grasses. However, the change in E. esula stems at GH was best explained by only 1998 E. esula stem counts and 2000 A. czwalinae/A. lacertosa abundance. These pre-treatment data provide insight into how differences between the two study sites ultimately may influence control of E. esula.

KEY WORDS: Euphorbia esula, biocontrol, invasives