Canadian Forest Service Publications

Assessing natural selection in white pine weevils (Pissodes strobi Peck) (Coleoptera: Curculionidae) for overcoming resistance in trees: An evolutionary model. 1997. Barclay, H.J. The Canadian Entomologist 129: 1105-1120.

Year: 1997

Issued by: Pacific Forestry Centre

Catalog ID: 4896

Language: English

CFS Availability: Order paper copy (free)

Mark record


An evolutionary model was constructed for the white pine weevil (Pissodes strobi Peck). This weevil attacks Sitka spruce [Picea sitchensis (Bongard) Carriere], and Sitka spruce trees have two forms, one being susceptible to the insect attacks and the other being resistant to attack. There is a fear that insects may develop tolerance to the resistant trees. The strategy of interplanting susceptible and resistant trees to minimize the likelihood of the insects developing tolerance mechanisms to circumvent the resistance is examined. It is found that if only one gene locus is involved, the development of tolerance occurs more quickly than if resistance is governed by two independent loci. The rate of evolution of tolerance to tree resistance is retarded by increased adult survivorship, the degree of recessiveness of the gene, preferential attack of susceptible trees, redistribution of intolerant insects from resistant to susceptible trees, and the immigration of wild-type insects.