The effect of thinning and clear-cut on changes in the relative abundance of root-feeding beetle (Coleoptera: Curculionidae) in Pinus taeda plantations in central Alabama and Georgia.

Background: Root-feeding beetles, particularly Hylastes spp., Hylobius pales Herbst and Pachylobius picivorus Germar, increase in abundance in stressed forest stands and vector Grosmannia and Leptographium spp. fungi, which contribute to southern pine decline (SPD) in the southeastern United States. This study examined changes in the relative abundance of root-feeding beetles in response to mechanical thinning and clear-cut of even-age loblolly pine (Pinus taeda L.) stands in central Alabama and Georgia every 2 weeks during a 30 month study in 2009-2012.

Results: The most abundant bark beetles were Hylastes salebrosus Eichhoff, H. porculus Erichson and H. tenuis Eichhoff. The relative abundance of the Hylastes spp. significantly increased after thinning treatments at all five sites. An initial decrease in Hylastes spp. occurred in response to clear-cut in some plots, but they typically recovered 2 months later and were stable for the remainder of the study.

Conclusion: This study reports on the relative abundance responses of pathogen-vectoring root-feeding beetles to a thinning and clear-cut treatment in P. taeda stands. Thinning treatments conducted during the summer and winter may increase the relative abundance of Hylastes spp., vectors of Leptographium and Grosmannia spp., which are known to contribute to SPD by triggering plants to release defensive volatile compounds.