Scots Pine Pinus Sylvestris Needles Research Articles

Effect of Scots pine needle age on preference, performance, and overwintering of pine-tree lappet larvae—the distaste for the oldest foliage

The choice of a host and feeding site is particularly interesting in the case of species feeding on conifers, where the larvae usually have a choice of several age classes of needles. The subject of this research is to answer whether the larvae have a specific preference for a certain needle age class, as well as how such foraging decisions influence larval performance and overwintering. We present the results of food choice tests and the influence of food quality (different age classes of Scots pine Pinus sylvestris needles) on the performance and overwintering of Dendrolimus pini larvae. The obtained results indicate that larvae fed with the youngest needles have the highest performance; however, in the food choice tests, one year old needles were chosen significantly more often. It was also shown that feeding on one year old needles led to the best overwintering survival. Differences in the contents of elements and metabolites explained the cause of the worst food, the oldest needles, and also the differentiation between current year and one year old needles. Water content may be of key importance, which is lower in one year old needles than in current year needles; its lower content may elevate the concentration of cryoprotectant substances.

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

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.