The range and response of Neonicotinoids on hemlock woolly adelgid, Adelges tsugae (Hemiptera: Adelgidae)
Hemlock woolly adelgid (HWA), Adelges tsugae Annand is a serious pest of eastern and Carolina hemlock in the eastern United States. A series of experiments compared commercially available and experimental insecticides, rates, application methods and timing for HWA control in Georgia and North Carolina. Safari 20 SG (dinotefuran) provided an average of 79 to 87% suppression of adelgid populations within one month after spring application. Arena 50 W (clothianidin) and Merit 75 WP (imidacloprid) were slower acting but provided longer-term adelgid suppression than dinotefuran. However, 26 months after application in spring 2006 HWA re-colonized trees treated with dinotefuran while imidacloprid treatments were still effective. High volume treatments like soil drenches of dinotefuran did not improve adelgid control over low volume applications such as soil injection. Evaluation in July 2008 of a fall 2007 application of Tristar 30 SG (acetamiprid) using arborjet trunk injectors showed no reduction of nymphal populations. Treatment timing and rates did not affect HWA relative to untreated check. The Xytect 75 WSP (imidacloprid) soil injection treatments applied during May, August, or November 2007 and Xytect root-fl are micro injection system treatment in November 2007 provided 99 to 100% control in all treatments.