1Chemical Ecology, Department of Plant Protection Sciences, Swedish University of Agricultural sciences, Box 44, 230 53 Alnarp, Sweden.
2Chemical Ecology, Department of Botany, Göteborg University, Box 461, 405 30 Göteborg, Sweden.
Nonhost volatiles affecting host selection of European conifer bark beetles, Ips typographus and Tomicus piniperda, have been investigated in lab and field. GC-MS analyses of the volatile constitutents of Betula pendula, B. pubescens, Populus tremula and Sambucus nigra intact leaves, showed both qualitatively and qantitatively differences among these non-host tree species and seasons. I. typographus antennae strongly responded to GLVs: (Z)-3-hexen-1-ol, 1-hexanol and (E)-2-hexen-1-ol in GC-EAD analyses of B. pendula, and B. pubescens aeration samples. In field trapping tests, the attraction of I. typographus, and T. piniperda were significantly reduced by single or blend of C6-OHs. Volatiles released from fresh bark chips of B. pendula, B. pubescens and P. tremula were also identified and quantified. Of which (E)-conophthorin elicited strong GC-EAD response in I. typographus. When this compound was added to pheromone trap, more than 50 % of trap catch reduction was achieved. A strong synergistic effect between (E)-conophthorin and GLVs (or Vn) was found, which seemed to totally block the pheromone attraction in I. typographus. Our results suggest that these non-host volatiles, characterising the wrong habitat (GLVs) and wrong tree species <like (E)-conophthorin> may explain part of the host selection behaviour of conifer bark beetles. They also offer a potential alternative management strategy for protecting host logs, trees, and stands.