Insect induced resistance in Lodgepole pine: effects on two pine feeding insects

Abstract

AbstractA series of experiments was performed in order to establish if the insect defoliators Panolis flammea (D&S) (Lept., Noctuidae) and Neodiprion sertifer (Geoff.) (Hym., Dripionidae) cause an induced response in lodgepole pine, Pinus contorta, and if so, what affect this response is likely to have on the two insects. Survival and growth of P. flammea was significantly affected by defoliation of seedling Skeena River lodgepole pine (KLP). On mature foliage from one forest site P. flammea larvae showed no significant difference in feeding preference between heavily defoliated trees and trees with less than 10% defoliation. On foliage from another forest site P. flammea larvae preferred trees with no previous defoliation. N. sertifer larvae significantly preferred foliage from previously defoliated trees. Insect defoliation of mature trees resulted in significant changes in the terpenoid compounds in leaf and stem resins. It is possible that both P. flammea and N. sertifer are affected by the carbon‐nutrient balance of their host. It seems that P. flammea however, unlike N. sertifer, is also affected by induced defences in lodgepole pine, particularly in younger trees. These differences are probably related to the feeding strategies of the two insects: P. flammea feeds on both current and previous year foliage, while N. sertifer feeds only on previous year foliage. The outbreak dynamics of P. flammea and N. sertifer in commercial lodgepole pine plantations are discussed in light of the results obtained.