Managing slash to minimize colonization of residual leave trees by Ips and other bark beetle species following thinning in southwestern ponderosa pine

Abstract

Due to high fire hazard and perceived reductions in forest health, thinning of small diameter trees has become a prevalent management activity particularly in dense stands. Creation of large amounts of logging slash, however, has created large quantities of habitat for bark beetles primarily in the Ips genus (Coleoptera: Curculionidae, Scolytinae). Evidence indicates that prior to Euro-American settlement fire played a major role in maintaining ponderosa pine stands in a condition that was much more open in structure than today (Cooper 1960, Covington and Moore 1994, Kolb et al. 1994). In general, lower tree densities led to increased tree growth (Ronco and Edminster 1985) and trees that were more vigorous and presumably less susceptible to insect attack (Kolb et al. 1998, Fettig et al. 2007). Bark beetles are a large and diverse subfamily of insects commonly recognized as the most important biotic mortality agent in western coniferous forests. Most bark beetles feed in the cambium and phloem and some species directly kill the host. These insects influence forest ecosystem structure and function by regulating certain aspects of primary production, nutrient cycling, ecological succession and the size, distribution and abundance of forest trees (Fettig et al. 2007). Attacks reduce tree growth and hasten decline, mortality and subsequent replacement by other tree species.

Citation

DeGomez, T., C.J. Fettig, J.D. McMillin, J.A. Anhold, and C.J. Hayes. 2008. Managing slash to minimize colonization of residual leave trees by Ips and other bark beetle species following thinning in southwestern ponderosa pine. Tucson, AZ: University of Arizona, College of Agriculture and Life Sciences Bulletin, AZ1448. 12 p.