Volatile profile differences and the associated Sirex noctilio activity in two host tree species in the Northeastern United States.

Sirex noctilio females are known to be attracted to stem sections of stressed pine trees for oviposition. The volatile profiles and attractiveness of Eastern white pine (Pinus strobus) and two chemotypes of Scots pine (P. sylvestris) were compared after stem injection with herbicide. In general, trap captures on herbicide-treated trees were higher than on controls. The high-carene chemotype of Scots pine captured the highest numbers of females, followed by the low-carene chemotype, and finally the Eastern white pine. Herbicide-treated trees of both species emitted larger quantities of volatiles than the controls. The herbicide treatment induced higher volatile emission rates in the Scots pine chemotypes than in white pine, although there was no difference between the two chemotypes. However, qualitative differences were found between the volatile profiles of the two species as well as between the two Scots pine chemotypes, which could account for the differential attractiveness of the species and chemotypes tested.