Predicted impacts of hard pine stem rusts on lodgepole pine dominated stands in central British Columbia

We developed two models to predict volume loss due to western gall rust (En docronartium harknessii (J.P. Moore) Y. Hiratsuka) and comandra blister rus t (Cronartium comandrae Peck) on juvenile lodgepole pine (Pinus contorta Do ugl. ex Loud.) dominated stands in central British Columbia. The models sug gest that volume loss is significantly and positively correlated to the inc idence of comandra blister rust. The relationship between volume loss and w estern gall rust incidence was weak. The addition of stand density data imp roved the statistical fit of the model. We used the growth and yield model Tree and stand simulator (TASS) to predict volume at culmination age (age a t which the merchantable mean annual increment was maximized) in thirty 1-h a stem-mapped stands. The lodgepole pine trees we stem mapped were also ass essed for hard pine stem rust incidence. We developed our volume loss funct ions assuming that trees with stem infections of both comandra blister rust and western gall rust were lethal, and that infected trees would die from ages 21 to 40. In areas where comandra blister rust is common, the losses d ue to the disease can be considerable. We predict that the volume losses du e to hard pine stem rusts in lodgepole pine dominated stands are as high as 7.2% by culmination age.