Biology of the Invasive Banded Elm Bark Beetle (Coleoptera: Scolytidae) in the Western United States

Abstract

Abstract The banded elm bark beetle, Scolytus schevyrewi Semenov (Coleoptera: Scolytidae), native to Asia, was detected in the United States in 2003, and as of 2011 it is known to occur in 28 states and four Canadian provinces. S. schevyrewi infests the same elm (Ulmus spp.) hosts as the long-established invasive, the European elm bark beetle, Scolytus multistriatus (Marsham). Information on the basic biology of S. schevyrewi in its native range is sparse; thus, we conducted laboratory studies and field studies in Colorado and Nevada. Comparisons of flight and behavioral responses were made with co-occurring S. multistriatus. When Siberian elm, Ulmus pumila L., cut logs (bolts) were allowed to be colonized by wild populations in the field, S. schevyrewi did not differ in emergence density from 10- versus 24-cm-diameter bolts. In the laboratory, S. schevyrewi readily colonized bolts of American elm, Ulmus americana L., but not Chinese elm, Ulmus parvifolia Jacq.; Siberian peashrub, Caragana arborescens Lam.; a cherry, Prunus fontanesiana (Spach) C. K. Schneid.; or Russian olive, Elaeagnus angustifolia L. In Colorado, S. schevyrewi often landed on elm bolts between 12:00 p.m. and 4 p.m.; and near large elm trees, they were captured more frequently on sticky traps at 1.8 and 3.7 m aboveground than higher along the main stem. In Colorado/Nevada, S. schevyrewi initiated flight in April/March and ceased in October/September, whereas S. multistriatus initiated flight in April/May and ceased in October/September. In funnel trap flight assays of semiochemicals in Colorado or Nevada, S. schevyrewi had moderate responses, 3–10-fold greater than unbaited control traps, to Multilure (a commercial lure for S. multistriatus), 2-methyl-3-buten-2-ol (MB) + multistriatin, and MB + a plant extract that is included in a commercial formulation of Multilure. In contrast, S. multistriatus had a 226–259-fold greater response to Multilure than to the control. Both Scolytus species showed electroantennographic (EAG) responses to MB, racemic multistriatin, and (+)- and (-)-α-inene, with the greatest sensitivity to multistriatin. S. schevyrewi was more responsive to (-)-α-pinene than was S. multistriatus.