title: Colonization Dynamics of Subcortical Insects on Forest Sites With Relatively Stressed and Unstressed Loblolly Pine Trees.
abstract: Loblolly pine (Pinus taeda L.) is the most important commercial tree species in the southeastern United States. Since the 1950s, there have been reports of loblolly pines showing reduced growth and increased mortality, particularly in central Alabama and western Georgia, United States; the phenomenon is termed as southern pine decline (SPD). Recently, the role of rhizophagous (root-feeding) insects in loblolly pine health within the context of SPD has come under greater scrutiny. We investigated the impacts of subcortical insects, particularly rhizophagous weevils (Coleoptera: Curculionidae), on loblolly pine health in northeastern Georgia. We created plots-representing a gradient of increased relative tree stress-from ungirdled trees, ungirdled trees baited with ethanol and turpentine (ungirdled-baited), and girdled trees. In total, 10,795 subcortical insects from four families (Buprestidae, Cerambycidae, Curculionidae, and Siricidae) and >82 species were trapped in two years. Almost half of the insects trapped (46% of individuals and 11% of species) were nonnative to North America. Insect captures in plots with girdled trees were 61 and 187% greater than those with ungirdled-baited and ungirdled trees, respectively. Tree treatment impacted captures of native, but not nonnative insects. Relative feeding area by the rhizophagous weevils Hylobius pales (Herbst) and Pachylobius picivorus (Germar) on pine twigs placed in pitfall traps was 1, 17, and 82% in plots with ungirdled, ungirdled-baited, and girdled trees, respectively. Hence, there was a strong association of native subcortical insects, especially rhizophagous weevils, with relatively highly stressed trees, confirming that they are secondary instead of primary pine colonizers.
authors.affiliation: Professorship of Forest Protection, Technische Universität Dresden, Pienner Strasse 8, 01737 Tharandt, Germany (Chr.Helbig@web.de), Daniel B. Warnell School of Forestry and Natural Resources, University of Georgia, 180 E. Green St., Athens, GA 30602 (drcoyle@uga.edu; kjgandhi@uga.edu).
authors.forename: Christiane E
authors.initials: CE
authors.lastname: Helbig
authors.affiliation: Daniel B. Warnell School of Forestry and Natural Resources, University of Georgia, 180 E. Green St., Athens, GA 30602 (drcoyle@uga.edu; kjgandhi@uga.edu).
authors.forename: David R
authors.initials: DR
authors.lastname: Coyle
authors.affiliation: USDA Forest Service, Southern Research Station, 200 W.T. Weaver Blvd., Asheville, NC 28804 (kklepzig@fs.fed.us).
authors.forename: Kier D
authors.initials: KD
authors.lastname: Klepzig
authors.affiliation: USDA Forest Service, Forest Health Protection, 200 W.T. Weaver Blvd., Asheville, NC 28804 (jnowak@fs.fed.us), and.
authors.forename: John T
authors.initials: JT
authors.lastname: Nowak
authors.affiliation: Daniel B. Warnell School of Forestry and Natural Resources, University of Georgia, 180 E. Green St., Athens, GA 30602 (drcoyle@uga.edu; kjgandhi@uga.edu), kjgandhi@uga.edu.
authors.forename: Kamal J K
authors.initials: KJ
authors.lastname: Gandhi
mesh_terms: D000818:Animals; D001517:Coleoptera / Q000502:physiology*; D020387:Food Chain; D005845:Georgia; D060434:Herbivory; D041603:Pinus taeda / Q000502:physiology*; D024301:Plant Bark / Q000502:physiology; D048889:Weevils / Q000502:physiology
keywords: Curculionidae; Pinus taeda; Scolytinae; pine decline; rhizophagous beetle