Impact of Debarking and Bark Grinding on Survival of Ips calligraphus (Coleoptera: Curculionidae: Scolytinae)

Chipping and debarking of infested woody material such as branches and logs are common sanitation methods used to kill bark- and wood-infesting insects. The sixspined ips, Ips calligraphus (Germar), is a native North American bark beetle (Coleoptera: Curculionidae: Scolytinae) that infests several pine (Pinus) species. We evaluated I. calligraphus mortality after debarking and grinding, using 12 recently cut longleaf pine (Pinus palustris Mill.) logs that had undergone natural colonization for three weeks in Florida. Initial bark beetle densities were estimated from samples collected the day before debarking. Similar amounts of bark were collected at three steps in the debarking and grinding processes: first immediately after debarking, and then after grinding and screening as either “fines” that fell through the screen, or as larger bark nuggets and flakes that stayed on top of the screen. Half the bark was inspected by hand on the day of debarking while the other half was placed in rearing cans and monitored for live beetles for the next 10 weeks. Percent mortality was estimated by comparing the number of emerged beetles collected from the rearing cans to the estimated initial adult beetle populations just prior to debarking. Overall, mortality was estimated at 99.4% after debarking and 100% after grinding for I. calligraphus, and 98.9% after debarking and 99.8% after grinding for the two smaller Ips species combined: Ips avulsus (Eichhoff) and Ips grandicollis (Eichhoff). These findings are discussed in relation to the Eurasian scolytine Tomicus piniperda (L.), a bark beetle similar in size to I. calligraphus, which was established throughout the Great Lakes region at the time of this study.