Assessing the establishment of Aphthona lacertosa and Aphthona nigriscutis introduced to control leafy spurge, Euphorbia esula.

摘要

Research was conducted to assess the establishment and control success of Aphthona spp. flea beetles introduced to control leafy spurge, Euphorbia esula L. in Minnesota. Leafy spurge is a Eurasian perennial plant that seriously impacts native plants, wildlife, and grazing land for cattle and horses. Since 1989, five species of flea beetles, Aphthona spp., were released in Minnesota to control leafy spurge. Some of the species, however, have had difficulty establishing and have not contributed to control success. Factors that may affect insect establishment include soil type, soil moisture, leafy spurge density, leafy spurge biotype, vegetation type, litter cover, release quantity, and interspecific competition.; Research results suggest that A. lacertosa is the most effective species in controlling leafy spurge in Minnesota. Aphthona lacertosa established at 100% of the release sites and significantly reduced leafy spurge stem densities by 73% across all sites studied. Aphthona nigriscutis established at 73% of the study sites, but at significantly lower densities than A. lacertosa. At a majority of the sites, significant reductions were achieved within two to three years after introduction of one or both species. Aphthona lacertosa, in particular, was able to establish growing populations in most sites and thus seems to be the more adaptable flea beetle species. Other introduced Aphthona spp. were difficult to locate in Minnesota and contributed little to the overall control success occurring statewide. There was no evidence of interspecific competition between A. lacertosa and A. nigriscutis. Small release quantities (500 beetles) can establish and potentially contribute to control success in Minnesota. Currently it is recommended that >1,000 beetles should be released at new leafy spurge infestations, but control was achieved in three years if 5,000 to 10,000 insects were released initially. Phenology models predicting first and peak emergence of A. lacertosa and A. nigriscutis were developed and tested for usefulness in other states. The results suggest that phenology models should be developed regionally to provide useful predictions for land managers. Maps were developed for Minnesota to spatially display dates of peak abundance for A. lacertosa and A. nigriscutis.