Detection and Seasonal Abundance of Sirex nigricornis and Eriotremex formosanus (Hymenoptera: Siricidae) Using Various Lures and Trap Trees in Central Louisiana, U.S.

Abstract

The recent introduction and spread of the nonnative woodwasp Sirex noctilio F. in North America has generated interest in the ecology of resident Siricidae. In 2 trapping experiments we compared 8 treatments for attractiveness to siricids. Four treatments consisted of traps baited with one of the following lure combinations: 70:30 α-β-pinene alone (Sirex lure); Sirex lure 95% ethanol; Sirex lure ipsenol ipsdienol; Sirex lure 95% ethanol ipsenol ipsdienol. The remaining treatments consisted of blank traps adjacent to standing, chemically debilitated Pinus taeda L. trap trees, created with either sodium N-methyldithiocarbamate (Woodfume®) and dimethyl sulfoxide, or Vanquish® herbicide (dicamba), on 2 separate dates. In a third experiment we compared trap catches among these 2 trap tree treatments and an ethanol lure using traps placed at 2 heights. We collected Sirex nigricornis F. in the fall months, with a peak in midNovember, and Eriotremex formosanus Matsumura in the spring, summer and fall, with a peak in midOctober. We collected no S. noctilio, nor males of any siricid species. The addition of ethanol and/or Ips sp. pheromones to the Sirex lure did not significantly improve collection of any siricids, and all semiochemical treatments were more effective for detecting S. nigricornis than trap trees. Traps positioned low upon dicamba-created P. taeda trap trees were most effective for detecting E. formosanus; however, no progeny emerged from trap trees. We provide detailed phenology and baseline data not previously reported on 2 species of Siricidae in central Louisiana.