SEASON-LONG INSECTICIDE EFFICACY FOR HEMLOCK WOOLLY ADELGID, ADELGES TSUGAE (HEMIPTERA: ADELGIDAE), MANAGEMENT IN NURSERIES

Nursery growers and extension personnel have to rely on efficacy data from forest and landscape systems to manage hemlock woolly adelgid in nurseries. Considerable differences in tree size and culture and application logistics could make such data unsuitable. We evaluated 12 different insecticide formulations for short and long-term control of hemlock woolly adelgid in container grown Eastern hemlocks, Tsuga canadensis. All products provided control of first generation hemlock woolly adelgids, though efficacy of foliar applications of neonicotinoids dinotefuran, imidacloprid (Marathon (R) II), and acetamiprid and foliar or drench applications of spirotetramat acted the most quickly. Foliar and soil applications of neonicotinoids and spirotetramat also prevented reinfestation of second generation crawlers. In contrast, second generation hemlock woolly adelgids successfully colonized trees treated with the contact insecticides, horticultural oil and bifenthrin. Systemic insecticides provided season-long control of hemlock woolly adelgid when applied to foliage, which is the preferred method of application of nursery growers.