Abietane and pimarane diterpene acid evolution in Scots pine Pinus sylvestris needles in relation to feeding of the pine sawfly, Diprion pini L

Abstract

the sawfly Diprion pini (Hymenoptera, Diprionidae) and results of the analyses were correlated with the feeding pattern of this insect in nature. An increase in resin acid concentration was observed during the growing season, but no direct relationship could be established with the feeding preferences of these insects. Young pines contained lower levels of abietane and pimarane diterpene acids than 10 or 30 year-old pines. Previous defoliation induced an increase in the neutral fraction and, although less so, in the diterpene acids in the needles formed the following year. The observed results are discussed in relation to the development of Diprion pini larvae and to previous hypotheses from other authors concerning the antifeedant properties of the resin acids. It is concluded that, if the abietane and pimarane diterpene acids interfere with the biology of Diprion pini, they cannot, however, be considered as the most important factors in the natural equilibria of this species.