Effects of Dinotefuran and Imidacloprid on Target and Non-target Arthropods on American Elm

Neonicotinoid insecticides are a relatively new class of compounds with excellent efficacy against a broad assemblage of key insect pests of woody plants. Unfortunately, the use of one neonicotinoid, imidacloprid, has been linked to secondary outbreaks of several species of spider mites on different trees and shrubs. Dinotefuran is another neonicotinoid insecticide now widely used by arborists to manage insects, including egregious borers like emerald ash borer. Researchers tested a hypothesis that applications of dinotefuran to American elms (Ulmus americana) elevated populations of a spider mite, Tetranychus schoenei, and rust mites in the family Diptilomiopidae, and found no indication that dinotefuran elevated densities of either mite. Applications of imidacloprid elevated densities of T. schoenei, but not Diptilomiopidae. Both neonicotinoids were highly efficacious in reducing abundances of European elm scale, Eriococcus spuria, and elm cockscomb gall aphid, Colopha ulmicola.