Stepwise multiple regression techniques were used to statistically analyze the relationships between damage caused by the pine needle sheath miner Zell-aria haimbachi (Busck); a needle miner, Oenerostoma etrobivorum (Zeller); sugar pine tortrix, Choriatoneura Zambertiana (Busck); and ambient and foliar concentrations of fluoride in lodgepole pine (Pinue contorta v. Zatifolia Engelm.) near the Anaconda Aluminum Company at Columbia Falls, Montana. Foliar fluoride concentration was significantly related (0.01 level) to needle miner damage and to damage caused by the pine needle sheath miner. The data strongly indicate that fluoride is a contributing factor in predisposing pines to damage by these insects.