Susceptibility of Pinus sylvestris provenances to needle‐eating diprionids

Abstract

The resistance of Pinus sylvestris of different geographical provenances was studied using biotests by rearing two species of diprionid sawflies (Neodiprion sertifer and Gilpinia paluda) on seven provenances in 1988 and on five in 1989. The larval groups were fed in the laboratory with branches from trees growing in orchards established in 1966. Tree origin affected larval success when estimated on the basis of larval periods, RGR and cocoon weight. Most of the provenances from the lake district of Finland were susceptible to sawflies. The northernmost provenance was also susceptible, thus indicating stress caused by the long transfer distance. The sawfly performance index correlated negatively with needle Mg and Pb concentrations, and positively with P, Cu and Zn. However, the C content best explained the sawfly success in stepwise regression analysis. Variation in resistance against defoliating insects could be used as a pest management strategy in practical silviculture.