A Comparison of Phenolic Constituents of Pinus monticola Resistant and Susceptible to Cronartium ribicola

Polyphenols and simple phenols in Pinus monticola Dougl. foliage and hark were studied in relation to host resistance to Cronartium ribicola J. C. Fisch. ex Rabenh. More than 50 phenolic substances were detected but no qualitative differences were found between resistant and susceptible trees. Some evidence is given for a quantitative relationship between one polyphenol in white pine foliage and resistance to blister rust. This compound may be a guaiacyl derivative. Differences in phenolics due to tree‐to‐tree variation, needle age, tissue (foliage versus bark), and season of year are also reported.