Arboriculture & Urban Forestry 39(5): September 2013 Arboriculture & Urban Forestry 2013. 39(5): 231–235 231 Effects of Dinotefuran and Imidacloprid on Target and Non-target Arthropods on American Elm Adrianna Szczepaniec, Brian B. Raupp, and Michael J. Raupp Abstract. 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, includ- ing 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. Key Words. Cockscomb Gall Aphid; Colopha ulmicola; Diptilomiopidae; Dinotefuran; Eriococcus spuria; European Elm Scale; Imidacloprid; Rust Mites; Secondary Pest Outbreak; Spider Mites; Tetranychus schoenei; Ulmus americana. Neonicotinoids are a relatively new and important class of systemic insecticides used to manage insect pests of many crops, including trees and shrubs. These nitroguanidine com- pounds affect a broad spectrum of insects by disrupting their acetylcholine nerve cell receptors (Mullins 1993). Of several neonicotinoid compounds introduced into the arboricultural marketplace, imidacloprid was the first to be widely used owing to its efficacy against several key insect pests of trees and shrubs including aphids (Sclar and Cranshaw 1996; Layton and Ma 2009), lace bugs (Gill et al. 1999; Szczepaniec and Raupp 2007), scales (Sclar and Cranshaw 1996; Frank 2012), psyllids (Young 2002), adelgids (Stewart and Horner 1994; Doccola et al. 2003; Webb et al. 2003; Cowles et al. 2006), palm bugs (Ali et al. 2010), leaf beetles (Sclar and Cranshaw 1996; Law- son and Dahlsten 2003), flatheaded borers (Herms 2003; Rebek et al. 2008; Smitley et al. 2010), roundheaded borers (Wang et al. 2005), leaf-feeding scarabs (Frank et al. 2007), and leafmin- ers (d’Eustachio and Raupp 2001; Gill et al. 2002). Not only did imidacloprid prove lethal to these pests, but it also reduced damage to red maple (Acer rubrum) caused by leafhoppers (Em- poasca fabae) and flatheaded appletree borers (Chrysobothris femorata) (Oliver et al. 2009; Oliver et al. 2010). Imidacloprid reduced defoliation of lindens (Tilia sp.) by Japanese beetles (Popillia japonica) (Frank et al. 2007) and periodical cicadas (Ahern et al. 2005). Imidacloprid also limited ash mortality associated with infestations of emerald ash borer (Agrilus pla- nipennis) (Rebek et al. 2008; Smitely et al. 2010). Due to its efficacy against wood-boring beetles, it has been widely recom- mended for controlling emerald ash borer (Herms et al. 2009) and used to treat thousands of trees to manage Asian longhorned beetle (Anoplophora glabripennis) (Szczepaniec et al. 2011). A second neonicotinoid, dinotefuran, entered the arboricultural trade several years after imidacloprid. Applications of dinotefuran have proven to be effective in controlling palm bug (Xylastodoris luteolus) (Ali et al. 2010), euonymus scale (Unaspis euonymi) (Frank 2012), crapemyrtle aphid (Tinocallis kahawaluokalani) (Layton and Ma 2009), California red scale (Aonidiella aurantii) (Ludwig 2011), potato leafhopper (Empoasca fabae) (Oliver et al. 2009), flathead appletree borer (Oliver et al. 2010), and hem- lock wooly adelgid (Adelges tsugae) (Frank and Lebude 2011). Despite their storied successes in controlling many important pests in landscapes, neonicotinoids have not been problem- free. Several cases of secondary pest outbreaks have now been linked to the application of neonicotinoids to trees and shrubs (Raupp et al. 2010). In 1998, Sclar et al. reported outbreaks of the honeylocust spider mite (Platytetranychus multidigituli) on honeylocust (Gleditsia triacanthos) following the applica- tion of imidacloprid. This report was soon followed by several others that documented outbreaks of spider mites following the application of imidacloprid. Elevated populations of mites were documented in plant-spider mite associations including hemlock (Tsuga canadensis) with spruce spider mite (Oligony- chus ununguis) (Raupp et al. 2004), rose bushes (Rosa sp.) with twospotted spider mites (Tetranychus urticae) (Gupta and Kris- chik 2007), elm (Ulmus americana) with Tetranychus schoenei (Szczepaniec et al. 2011), and boxwood (Buxus sempervirens) with boxwood spider mite (Eurytetranychus buxi) (Szczepaniec and Raupp 2012a; Szczepaniec and Raupp 2012b). Spider mite outbreaks on elms and boxwoods following applications of imi- dacloprid were linked to enhanced fecundity of spider mites following consumption of foliage from plants treated with imida- cloprid (Szczepaniec et al. 2011; Szczepaniec and Raupp 2012b). ©2013 International Society of Arboriculture
September 2013
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