Season-Long Insecticide Efficacy for Hemlock Woolly Adelgid, Adelges Tsugae (Hemiptera: Adelgidae), Management in Nurseries (Report‪)‬

Hemlock woolly adelgid, Adelges tsugae (Annand), has devastated stands of Eastern hemlock, Tsuga canadensis L., and Carolina hemlock, T. caroliniana Engelmann, in 18 states from Maine to Georgia (USFS 2011a). Hemlock woolly adelgid has also become a major pest of hemlocks in ornamental landscapes and urban forests where hemlocks are planted as hedges, shrubs, and shade trees (McClure 1987; Quimby 1996; Raupp et al. 2008). Hemlock woolly adelgid feeding depletes trees of carbohydrates and other resources and rapidly reduces the health and aesthetic value of trees (McClure et al. 2001). Trees lose their characteristic dark green color that is valued in ornamental landscapes and instead become gray, palegreen, or yellow (McClure 1987). Infestation also causes bud mortality, needle loss, reduction of new growth, branch dieback, and tree death (McClure 1987; McClure et al. 2001). Nurseries that produce hemlocks for ornamental landscapes are typically within the native range of hemlock forests. These hemlock trees are subject to a constant influx of hemlock woolly adelgid crawlers carried by wind or animals (McClure 1990). Growers from locations with active hemlock woolly adelgid infestations are prohibited from selling plants to many states that have established quarantine laws (USFS 2011b). Even shipments within quarantine areas must be adelgid free to prevent rejection by customers or agriculture inspectors. Importantly, transportation of nursery stock is a primary mechanism of long-distance transport of hemlock woolly adelgid (USFS 2005).