C. E. Jones, N. P. Havill, J. L. Hanula, S. K. Braman
Journal of Entomological Science 49 (4), 383-400, (1 October 2014) https://doi.org/10.18474/0749-8004-49.4.383
KEYWORDS: Adelges tsugae, Laricobius nigrinus, Laricobius rubidus, Sasajiscymnus tsugae, biological control
Eastern hemlock, Tsuga canadensis (L.) Carrière, and Carolina hemlock, Tsuga caroliniana Engelmann, provide unique habitat that is threatened by the invasive hemlock woolly adelgid, Adelges tsugae Annand, which arrived in Georgia in 2003. In an attempt to conserve a portion of the mature hemlocks in north Georgia, the USDA Forest Service created over 100 Hemlock Conservation Areas throughout the Chattahoochee National Forest and designated them to receive chemical and/or biological control. Sasajiscymnus tsugae Sasaji and McClure, Laricobius nigrinus Fender, and Scymnus sinunodulus Yu and Yao are predatory beetles reared in the laboratory and released in these areas. To determine establishment of these predators, infested hemlock trees were sampled during spring 2010 - 2012 at some of these release sites. Additionally, nonrelease sites, 0.4 -1.6 km from release areas, were sampled in 2012 to evaluate predator spread from release trees. Five hundred ninety-two S. tsugae, 232 L. nigrinus, 262 native L. rubidus, and 58 Laricobius hybrids were recovered at multiple sites over those years. Sasajiscymnus tsugae was found at 3 sites, 3 years after release and at 2 other sites, 2 years after release. Laricobius nigrinus was found at 1 site, 3 years after release and at 2 sites, 2 years after release. Scymnus sinunodulus was never recovered. Our results demonstrate that S. tsugae and L. nigrinus are established in north Georgia, and that the native L. rubidus is commonly associated with A. tsugae and is hybridizing with L. nigrinus; however, the population sizes, efficacy, and survival rates of all these predators are still unknown.