Defensive resin characteristics of two host pine species of the southern pine beetle

 

The southern pine beetle, Dendroctonus frontalis (Coleoptera: Scolytidae) is a major pest in pine forests of the southeastern United States, killing thousands of acres of trees, and causing millions of dollars in damage every year.  Although D. frontalis is known to attack and kill at least seven species of pine, beetle infestations are predominantly found in loblolly pine, Pinus taeda.  This landscape scale pattern of infestations suggests that P. taeda must be the preferred host for these beetles. Because trees defend themselves against beetle attacks using their resin defense systems, trees with high resin volumes make poor hosts.  It is thought that P. taeda has a smaller volume of resin than other Pinus species, in particular Longleaf pine, Pinus palustris. This trait is one that would make it a desirable host for the beetles and would explain the landscape scale pattern of infestations. To test the hypothesis that these two pine species differ in resin volume, I sampled trees of both species in multiple forests and during different parts of the growing season.  I found that when these two species are growing together on the same site there is no difference in the volume of constitutive resin or in the amount of resin produced by inducing a defensive response.  When trees were sampled in pure stands, grown separately and sampled as they appear in the landscape, there was also no difference in the volume of resin between the two species.