Screening spruce for white pine weevil resistance

• Project description
• Distribution of P. strobi in North America
• Genetic variation in canadian weevil populations
• Range of Sitka spruce
• Sources tested for resistance in Western North America
• White pine weevil resistance screening trials
• Mass screening for resistance (Jordan River plantation)
• Ghost trial: studies using caged insects clarified the mating system of weevils
• Artificial wounding studies: Studying plant defenses
• Insect - plant relationships
• Are weevil resistant trees also resistant to other insects?
• Conclusions
• Selected references

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Are weevil resistant trees also resistant to other insects?

While the implementation of weevil resistant genotypes in spruce regeneration programs will reduce damage by the white pine weevil, there are a number of other insect pests that also have an impact on spruce regeneration. For example, the spruce bud moth, Zeiraphera canadensis, and Cooley spruce gall aphid (Adelges cooleyi) can stunt and deform trees. A given suite of mechanisms that confer resistance to weevil may or may not confer resistance to other pests. As a result, some genotypes that are resistant to weevil may also be resistant to other pests, while others may be more susceptible.

In order to protect the investment made in identifying and propagating weevil resistant spruce, and to effectively use these genotypes in reforestation programs, we conducted a study to determine the susceptibility of weevil resistant Sitka and interior spruce to incidence of damage by other insect pests. To achieve this, ground surveys were carried out in 5 of our weevil screening trials. Other than the white pine weevil, the insects that had the greatest impact on resistant and susceptible spruce were gall aphids, the spruce bud moth Zeiraphera canadensis and the spruce cone worm Dioryctria reniculelloides.

We concluded that resistant and susceptible trees performed similarly with respect to damage by other insect pests. While incidence of insect damage was not influenced by weevil resistance status, observations at the family and clonal line level indicated variation in performance with respect to specific insect pests. Individual weevil resistant families and clonal lines with good height growth and stem form as well as better than average performance with respect to insect pests were identified at some of the sites. This information will be useful in selecting weevil resistant material for inclusion breeding programs and seed orchards.

 

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