|Jacobs, James - MONTANA STATE UNIV|
Submitted to: Journal of Range Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 7, 2006
Publication Date: September 1, 2006
Citation: Jacobs, J.S., Sheley, R.L. 2006. Integrated Management of Leafy Spurge Infested Rangeland. Journal of Range Management. 59(5):475-482. Interpretive Summary: Leafy spurge is a major invasive weed that dominates millions of acres and continues to spread throughout the west US. We attempted to develop an integrated management program for leafy spurge by determine the effects of multi-species grazing combined with a biological control agent, the flea beetle. Grazing initially increased leafy spurge density, it decreased leafy spurge density after the first 3 years. Leafy spurge flowering stems were decreased from 80 to 4 stems per square yard. The decrease was more rapid when grazing was combined with the flea beetles. These results suggest managers can control leafy spurge with grazing and can accelerate the rate of control by adding flea beetles.
Technical Abstract: Our objective was to determine the effects of multispecies grazing combined with Aphthona on leafy spurge infested rangeland. On two western North Dakota sites divided into pastures 25 to 79 hectares, two grazing duration treatments were applied, season-long with 7 to 10 cow calf pairs and 20 to 25 sheep from late May through mid September, and rotation with 18 to 21 cow calf pairs and 45 to 50 sheep for 3 weeks twice per years. Grazing treatments started in 1998 and continued through 2002. Aphthona spp. were released beginning in 1991 and were widespread in both pastures by 1998. Four grazing exclosures were randomly located in each pasture in the spring of 1998. Cover of leafy spurge, grass, and forbs, as well as density of vegetative and flowering leafy spurge stems were measured in July 1998 through 2002. Aphthona densities were counted July 1999 through 2002. Grazing initially increased leafy spurge vegetative stem density, but grazing decreased vegetative stem density from 104 in 1999 to 20 stems/m2 in 2002. Season-long grazing reduced vegetative stem density by over 30 stems/m2 compared to rotation grazing. Leafy spurge flowering stems decreased from 80 stems/m2 in 1998 to 4 stems/m2 in 2002 in all treatments. The decrease was more rapid when grazing was combined with Aphthona. Initially, Aphthona densities were greater in the grazed areas than the exclosures, but by 2002 more Aphthona were found in the exclosures than the grazed areas. Grazing reduced grass cover, while grazing increased forb cover. Results suggest a synergistic effect of combining multispecies grazing and Aphthona when restoring spurge-infested grasslands.