Canadian Forest Service Publications
Resistance against Pissodes strobi (Coleoptera: Curculionidae) in severed leaders and in a water-soluble bark extract of Picea sitchensis (Pinaceae): evidence for a post-ingestive mode of action. 2001. Sahota, T.S.; Manville, J.F.; Hollmann, J.; Leal, I.; Ibaraki, A.I.; White, E.E. The Canadian Entomologist 133: 315-323.
Issued by: Pacific Forestry Centre
Catalog ID: 18326
Availability: Order paper copy (free)
The levels of ovarian growth and transcription of the vitellogenin gene were compared in Pissodes strobi Peck (Coleoptera: Curculionidae) feeding on severed leaders from susceptible and resistant Picea sitchensis (Bong) Carr (Pinaceae) and in weevils given a dose of an aqueous extract from the bark of such leaders. A force-feeding method was developed to deliver the extracts into the alimentary canal of the weevils. Weevils given one dose of the aqueous extract from resistant leaders, followed by feeding on sections of laterals from susceptible trees, exhibited a 60% inhibition of oocyte growth relative to insects given the extract from susceptible leaders. In similar experiments, transcription of the vitellogenin gene of the weevils was inhibited by about 48%. Transcription of the vitellogenin gene was reduced by about 60% in weevils feeding on the severed leaders from the resistant clone relative to those feeding on severed leaders from susceptible trees. Results indicate that these effects of resistance do not require an intact tree. Experiments using extracts show that observed effects result from a post-ingestive effect of the extract.