Chemical and nutritional status of dwarf mistletoe, Armillaria root rot, and Comandra blister rust infected trees which may influence tree susceptibility to bark beetle attack

The terpenoid and phenyl propanoid content of xylem resin as well as phloem nitrogen and carbohydrate levels of lodgepole pine trees infected with Armillaria root disease, Comandra blister rust, and dwarf mistletoe and check (asymptomatic) trees were determined. Comparisons were made to determine if differences existed that might influence their susceptibility to bark beetle attack. These variables were also contrasted with respect to aspect (north and south). Five volatiles (tricyclene, α-pinene, camphene, γ-terpinene, and bornyl acetate) were significantly higher in trees with one or more diseases than in check trees. Four volatiles (myrcene, camphor, 4-allylanisole, and γ-terpineol) were significantly lower in diseased trees. Camphene was the only resin constituent found to differ with respect to aspect, with a higher concentration on the north aspect of check trees. There were no significant differences in carbohydrate or nitrogen content with respect to aspect. The check trees were found to have significantly higher starch, total nitrogen, and free amino-N contents than diseased trees. Trees infected with Comandra blister rust were found to contain lower levels of reducing and nonreducing sugars than the other diseased trees and the check trees. Changes in terpenoids and phenyl propanoids in trees susceptible to mountain pine beetle attack suggest a biochemical basis for host selection. Key words: mountain pine beetle, lodgepole pine, Comandra blister rust, dwarf mistletoe, Armillaria root disease, resin chemistry, susceptibility.