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Individual Highlight

Using Predators and Chemicals together to Protect Hemlock Trees.

Photo of A bundle of hemlock foliage used to release Laricobious predator beetles into the forest canopy to control hemlock woolly adelgid. USDA Forest ServiceA bundle of hemlock foliage used to release Laricobious predator beetles into the forest canopy to control hemlock woolly adelgid. USDA Forest ServiceSnapshot : A non-native insect, the hemlock woolly adelgid, is eliminating an ecologically important tree species, eastern hemlock, from southern Appalachian forests. Systemic insecticide applications and predator beetle releases are being combined to fight this invasive pest. In a study in northern Georgia, trees previously treated with imidacloprid insecticide had better crown health and eventually supported as many predator beetles as untreated trees, showing promise for an integrated pest management approach.

Principal Investigators(s) :
Mayfield, Albert (Bud) E., IIIHanula, James L.
Research Location : Chattahoochee National Forest, Georgia
Research Station : Southern Research Station (SRS)
Year : 2015
Highlight ID : 928

Summary

Mortality of eastern hemlock in the southern Appalachian Mountains is rapid and likely outpaces the ability of introduced predator beetles to establish, increase in number, and control adelgid populations. In a recent study in northern Georgia, Forest Service scientists and their university partners examined the potential for combining chemical insecticide treatments and predator releases (biological control) in the same stands. Hemlock trees treated with a low rate of imidacloprid insecticide had better crown health and eventually supported as many or more adelgid prey and beetle predators (Laricobius nigrinus) than untreated trees. Using cages to exclude predators from selected branches, the researchers also showed that predators significantly reduced adelgid populations during the winter and early spring. Results suggest the potential to expand an integrated approach to hemlock woolly adelgid management and help slow the pace of hemlock decline.

Forest Service Partners

External Partners

  • Nathan P. Havill, USDA Forest Service, Northern Research Station, Hamden, CT
  • Andrew R. Tait, University of North Carolina Asheville, Asheville, NC
  • Ashley B. Galloway, University of Tennessee, Entomology and Plant Pathology Dept., Knoxville, TN
  • Barbara C. Reynolds, University of North Carolina Asheville, Asheville, NC
  • Carla I. Coots, University of Tennessee, Entomology and Plant Pathology Dept., Knoxville, TN
  • Cavell Brownie, Raleigh, NC
  • Shimat V. Joseph, University of Georgia, Department of Entomology, Griffin, GA

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