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1 July 2015 Long Term Outcomes of Population Suppression of Leafy Spurge by Insects in the Mountain Foothills of Northern Utah
Jacob M. Anderson, Samantha A. Willden, Dallin L. Wright, Edward W. Evans
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Abstract

In North America host-specific flea beetles (Aphthona spp.; Coleoptera: Chrysomelidae) from Europe have been introduced to suppress invasive populations of the exotic forb, leafy spurge, Euphorbia esula L. (Euphorbiaceae). Long term outcomes of such introduction were examined in 2013 for a spurge infested site (managed as elk winter range) in the mountain foothills of northern Utah where three species of flea beetles had been released two decades earlier, in the 1990s. The abundance of leafy spurge at the site had declined by 2013 to only 4% of its abundance in 1995. The three species of flea beetles (dominated by A. lacertosa Rosenhauer) persisted in low numbers at the site in 2013 [peaking at 7-8 adults (all species combined) per 100 stems and inflicting aboveground feeding damage to all spurge stems by late summer]; flea beetle abundance had declined by 89-97% from high numbers as sampled in 2001. Another biocontrol insect, the stem borer Oberea erythrocephala Schrank (Coleoptera: Cerambycidae), had immigrated on its own to the site (as first detected in 2008) and, by mid-July in 2013, had damaged all spurge stems (typically causing total loss of the inflorescence on flowering stems). With the collapse of the spurge population at the site, the biomass of grasses [dominated by the exotic Bromus inermis Leyss and Arrhenatherum elatius (L.)] and forbs increased by 269% and 507%, respectively, from 1995 to 2013. These increases in grasses and forbs at the site with insect suppression of leafy spurge have resulted in more favorable habitat for elk and other wildlife.

© 2015 American Midland Naturalist
Jacob M. Anderson, Samantha A. Willden, Dallin L. Wright, and Edward W. Evans "Long Term Outcomes of Population Suppression of Leafy Spurge by Insects in the Mountain Foothills of Northern Utah," The American Midland Naturalist 174(1), 1-13, (1 July 2015). https://doi.org/10.1674/0003-0031-174.1.1
Received: 7 August 2014; Accepted: 1 March 2015; Published: 1 July 2015
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