Impacts of basal area on subcortical insect assemblages in longleaf pine (Pinus palustris) of southwest Georgia

Longleaf pine (Pinus palustris) trees have historically been considered less susceptible to subcortical insect outbreaks compared to loblolly pines (Pinus taeda) in the southeastern United States. Though many studies have compared longleaf and loblolly pine oleoresin systems, the tree’s main defense against bark beetles, few have studied how stand characteristics and silvicultural practices in longleaf pine stands affect subcortical insect assemblages. Unlike loblolly pines, longleaf pines are rarely planted in high basal area plantations, which could result in fewer bark beetle outbreaks. We examined the effects of basal area on bark beetle assemblages in longleaf pine stands of southwest Georgia. Subcortical insects were captured in three stand types: (1) mature low basal area (>90 ft²/ac) longleaf pine stands to determine the typical subcortical insect assemblage present (N=6); (2) 20 year old high basal area (>100 ft²/ac) longleaf plantations resembling loblolly plantations (N=6); and (3) mature high basal area longleaf stands (N=3). Total numbers of bark beetles was lowest in the 20 year old high basal area longleaf plantation stands and highest in the mature high basal area longleaf stands. This suggests that stand age may have a greater impact than basal area on subcortical insect assemblages. Results from this study could lead to better management techniques for reducing bark beetle populations in longleaf pine stands in the Southeast.