Document Type

Thesis - University Access Only

Award Date

2004

Degree Name

Master of Science (MS)

Department / School

Biology and Microbiology

First Advisor

Jack Butler

Abstract

A 6-year study was conducted in the northern mixed-grass prairie to assess the efficacy of flea-beetles (Aphthona lacertosa and A. nigriscutis) as bio[1]control agents of leafy spurge (Euphorbia esula L.) and to characterize the response of the resident vegetation. Sixty-two release plots and 31 non-release plots were established in southeast Montana and northwest South Dakota in 1998. Attempts were made to match non-release plots to release plots by slope, aspect, vegetation composition, and landform features. Beetle abundance and composition were evaluated annually from 1999 through 2003. Vegetation composition and foliar cover and leafy spurge foliar cover were estimated annually (1998, 2000-2003). Black beetles (A. acertosa) were approximately 9 and 17 times more abundant than brown beetles (A. nigriscutis) in Montana and South Dakota, respectively. By 2000, black beetle populations had increased 7.5 fold in Montana and 14 fold in South Dakota, compared to 1998 values. Concomitant with the exponential growth of beetles, leafy spurge foliar cover was significantly reduced by 76% in Montana and 62% in South Dakota, within two years following release. Overall, beetle establishment and persistence was not influenced by slope (moderate or steep) or moisture regime (mesic and xeric). V By 2003, leafy spurge foliar cover had been reduced 80-100% on all study plots (release and non-release) in the study area. Graminoid foliar cover increased 40% by 2001 in Montana and 19% in South Dakota. In 2003, an additional 29 non-infested plots were established in the study area corresponding to their infested counterparts by range site. Non-infested plots contained significantly greater mean species richness than either release or non-release plots in Montana and greater mean species richness than release or non-release plots in South Dakota.

Library of Congress Subject Headings

Leafy spurge -- Biological control -- Montana.
Leafy spurge -- Biological control -- South Dakota.
Flea beetles.

Publisher

South Dakota State University

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Rights Statement

In Copyright