INSECT INDUCED RESISTANCE IN LODGEPOLE PINE - EFFECTS ON 2 PINE FEEDING INSECTS

A series of experiments was performed in order to establish if the ins ect defoliators Panolis flammea (D&S) (Lept., Noctuidae) and Neodiprio n sertifer (Geoff.) (Hym., Dripionidae) cause an induced response in l odgepole pine, Pious 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 lod gepole pine (KLP). On mature foliage from one forest site P. flammea l arvae showed no significant difference in feeding preference between h eavily defoliated trees and trees with less than 10% defoliation. On f oliage from another forest site P. flammea larvae preferred trees with no previous defoliation. N. sertifer larvae significantly preferred f oliage from previously defoliated trees. Insect defoliation of mature trees resulted in significant changes in the terpenoid compounds in le af and stem resins. It is possible that both P. flammea and N. sertife r are affected by the carbon-nutrient balance of their host. It seems that P. flammea however, unlike N. sertifer, is also affected by induc ed defences in lodgepole pine, particularly in younger trees. These di fferences are probably related to the feeding strategies of the two in sects: P. flammea feeds on both current and previous year foliage, whi le N. sertifer feeds only on previous year foliage. The outbreak dynam ics of P. flammea and N. sertifer in commercial lodgepole pine plantat ions are discussed in light of the results obtained.