Aphthona nigriscutis Foudras, a biological control agent for Euphorbis esula L. (Leafy Spurge)has been established in Fremont County, Wyoming since 1992. Near one A. nigriscutis release site a mixed stand of E. esula and a native plant, Euphorbia robusta Engelm., was discovered in 1998. During July of 1999, A. nigriscutis adults were observed feeding on both E. esula and E. robusta. A total of 31 E. robusta plants were located and staked on about 1.5 hectares of land which had a visually estimated E. esula ground cover of over 50%. Eighty-seven percent of the E. robusta plants showed adult feeding damage. There was 36% mortality for plants with heavy feeding, 12% mortality for plants with light feeding and no mortality for plants with no feeding. By August of 2002, the E. esula ground cover had declined to less than 6% and the E. robusta had increased to 542 plants of which only 14 (2.6%) showed any feeding damage. For the four-year period, the E. esula ground cover was inversely correlated to the E. robusta density and positively correlated to A. nigriscutis feeding damage showing that as E. esula ground cover declines so does adult Aphthona nigriscutis feeding on E. robusta.
Species 1: Coleoptera Chrysomelidae Aphthona nigriscutis
Species 2: Euphorbiales Euphorbiaceae Euphorbia esula (leafy spurge)
Species 3: Euphorbiales Euphorbiaceae Euphorbia robusta
Keywords: Biological Control
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