title: Within-tree distributions of the Sirex noctilio Fabricius (Hymenoptera: Siricidae)--parasitoid complex and development of an optimal sampling scheme.
abstract: Little is known about the introduced European woodwasp, Sirex noctilio F. (Hymenoptera: Siricidae), and its hymenopteran parasitoid complex in North America. To assess within-tree and landscape-level densities and distributions of these insects, and develop a more cost effective approach  for sampling and monitoring S. noctilio, 18 infested pines (12 P. resinosa Aiton and six P. sylvestris L.) were felled from six stands within three regions in central New York and cut into 0.5-m bolts. Bolts were carefully split to recover all siricids (S. noctilio and native siricids) and  parasitoids. In total, 2,558 siricids were recovered; 1,972 siricid larvae and 586 teneral adult S. noctilio. Parasitism of siricids, a majority of which were S. noctilio based on larval rearing results, was 16.4% with Ibalia leucospoides ensiger Norton causing 10.7% of the documented mortality.  Numbers of siricids and parasitoids declined 33-86% from the northern to the southern sampling regions, peak insect densities occurred in sections of the bole 15-19 cm in diameter and numbers of insects were generally higher in P. sylvestris than P. resinosa according to the  highest ranked zero-inflated poisson and probit regression models. Bark thickness was not correlated with siricid or parasitoid species densities. We also describe sampling plans where as few as two 0.5-m samples from infested trees provided reliable within-tree insect densities.
authors.affiliation: State University of New York College of Environmental Science and Forestry, Syracuse, NY 13210, USA.
authors.forename: P T
authors.initials: PT
authors.lastname: Eager
authors.forename: D C
authors.initials: DC
authors.lastname: Allen
authors.forename: J L
authors.initials: JL
authors.lastname: Frair
authors.forename: M K
authors.initials: MK
authors.lastname: Fierke
mesh_terms: D000818:Animals; D006790:Host-Parasite Interactions; D041605:Pinus sylvestris / Q000469:parasitology*; D024301:Plant Bark / Q000469:parasitology; D011156:Population Density; D014863:Wasps / Q000469:parasitology* / Q000502:physiology