Biological control and hyperspectral remote sensing of leafy spurge (Euphorbia esula L.) an exotic plant species in North America

Leafy spurge (Euphorbia esula L.) is an adventive, invasive, plant species in North America. Aphthona lacertosa and A. nigriscutis are flea beetles (Coleoptera: Chrysomelidae) introduced for biological control of leafy spurge in North America. This research directly addresses the need for quantitative assessment of biological control and for regional scale mapping of leafy spurge infestations.; This research had three main objectives. The first was to document the establishment and impact on leafy spurge populations of introduced Aphthona flea beetles. In 1998, 3,000 beetles of each species (6,000 total per site) were released on 76 of 101 monitoring sites in Wyoming. Flea beetle abundance, leafy spurge canopy cover, and flea beetle impact area were measured in 1999 and 2000. After two years, Aphthona releases resulted in significant reductions in leafy spurge canopy cover (from 49% to 6%) with suppression of leafy spurge averaging 285 m2. Flea beetles were effective in controlling leafy spurge regardless of the site characteristics (vegetation type, topographical position, soil type, and aspect) and initial leafy spurge canopy cover.; The second objective was to develop methods for detecting and estimating leafy spurge abundance from remotely sensed data. Ground spectrometer data demonstrated that leafy spurge was spectrally distinct due to its conspicuous yellow-green bracts. Mixture Tuned Matched Filtering was used to estimate leafy spurge canopy cover and map leafy spurge distribution from Airborne Visible/Infrared Imaging Spectrometer imagery acquired in 1999. Overall performance of MTMF for estimating percent cover of leafy spurge for all sites was good (r2 = 0.69) with better performance in prairie areas (r 2 = 0.79) and poorer performance occurring on wooded sites (r 2 = 0.57).; The third objective was to assess the accuracy of using remotely sensed data for mapping leafy spurge in various habitat types. Leafy spurge was mapped with an overall accuracy ranging from 84% to 95%, depending on the classification criteria employed. Hyperspectral remote sensing data provide an accurate method of mapping leafy spurge at regional scales.