Effect of Laricobius spp. (Coleoptera: Derodontidae) and Leucotaraxis piniperda (Diptera: Chamaemyiidae) predation on hemlock woolly adelgid (Hemiptera: Adelgidae) and on eastern hemlock (Pinales: Pinaceae) health in the eastern United States
| Authors: | Carrie E Preston, Timothy Shively, Mark C Whitmore, Jerome F Grant, Albert (Bud) E. Mayfield, Timothy Tomon, Nathan P. P. Havill, Zephyr Zembrzuski, John Seiler, Scott M Salom, Michael Brewer [editor] |
| Year: | 2026 |
| Type: | Scientific Journal |
| Station: | Southern Research Station |
| DOI: | https://doi.org/10.1093/jee/toag202 |
| Source: | Journal of Economic Entomology |
Abstract
In the eastern United States, feeding by introduced predators Laricobius nigrinus Fender and Laricobius osakensis Shiyake and Montgomery are likely insufficient to sustainably regulate the invasive hemlock woolly adelgid (HWA), Adelges tsugae Annand, due to adelgid population rebound postpredation. This suggests that additional predators may be needed in eastern North America to achieve effective biological control. In the Pacific Northwest, there is evidence that multiple specialist predators, including La. nigrinus, Leucotaraxis piniperda (Malloch), and Le. argenticollis (Zetterstedt) contribute to maintaining HWA populations below damaging levels on western hemlock. We report on a 2-yr, 5-location study to evaluate the combined effect of predators, La. nigrinus, La. osakensis, and Le. piniperda on HWA populations and eastern hemlock health in the eastern United States. Three assessments targeting different stages of predator-prey activity were conducted annually by installing mesh cages on HWA-infested branches where La. nigrinus was established. Predation by Laricobius spp. caused measurable spring HWA ovisac disturbance, and Le. piniperda predation caused measurable summer HWA ovisac disturbance during both years. Proportion of new shoot growth and mean length of new shoot growth did not differ among treatments for both years. This suggests that a longer-term study may be needed to better understand the combined effects these predators may have on eastern hemlock health, or that additional predators such as Le. argenticollis should also be evaluated.