Comparing flight patterns of the native woodwasp, Sirex nigricornis F., with Sirex noctilio, a non-native threat to southeastern pine stands

Sirex nigricornis F. (Hymenoptera: Siricidae) inhabits dead, or dying, pine trees in its native range of the eastern U.S. and Canada.  In contrast, S. noctilio has been reported killing healthy trees in regions where it has been accidentally introduced.  Until 2004, these introductions had all been in the Southern Hemisphere where pines, and their associates, are also exotic.  However, in 2004 the invasive was discovered in New York and has been spreading throughout the northeastern U.S. and southern Ontario.  This discovery presents a significant threat to the economically and ecologically important pine stands of the Southeast.  To try and predict possible interactions among these species we trapped S. nigricornis in Arkansas from October through December from 2009 through 2012 and compared their flight patterns to previous studies describing S. noctilio emergence.  Both species exhibited non-linear and linear patterns of emergence and flight which changed from year to year.  Flight periods were significantly different between the two species suggesting different physiological requirements for development.  These differences may indicate many important interactions among S. noctilio and native pine-associates.  Experiments elucidating relationships among various mortality factors will be important in determining which interactions are most likely to occur in the future.