Site and Stand Conditions Associated with Southern Pine Beetle Outbreaks in Arkansas—A Hazard-Rating System
Abstract Since 1969, the southern pine beetle (SPB, Dendroctonus frontalis, Zimm) has spread northwest through 24 southern Arkansas counties. Analysis of trees in 984 infested plots indicated that attacked trees were in a stressed state with smaller crowns, thinner bark, and slower growth than unattacked trees. Comparison with 509 uninfested plots showed trees on infested plots had slower growth rates, thinner bark, and occurred on sites with lower site index and less slope. Disturbance, notably lightning and logging, significantly increased a stand's susceptibility to beetle attack. Undisturbed infested plots were significantly younger with smaller stand d.b.h. and higher basal area than undisturbed uninfested plots. All factors which reduced radial growth predisposed stands to SPB attack, but high stand density had the most significant influence. The hazard-rating system presented indicates a pine stand's susceptibility to attack. Reduction of basal area to below 100 square feet per acre in carefully conducted thinning operations is the recommended practice to minimize SPB losses.