Needle-Bearing Internodes on Western White Pine Reproduction in Relation to Blister Rust Infection

It has been quite definitely established that the current season's shoots of western white pine are relatively resistant to infection by blister rust, and to a lesser extent that this resistance is actually a characteristic of the needles on that year's growth. To obtain information indicative of the proportion of the target comprised by needles of the current season, 24 young pine trees were studied somewhat in detail. Although the data are by no means considered final, they are presented here as an approximate indication of the relative numbers of slightly and highly susceptible needles present on young western white pines of various ages.