Examination of Douglas-fir clones for differences in susceptibility to damage by cone and seed insects

Abstract

In 1974 and 1976, Douglas-fir cones from 51 clones and 150 clones, respectively, were collected and determinations were made of the percentage of seed damaged by the cone insects <i>Barbara colfaxiana</i>, <i>Contarinia oregonensis</i>, <i>C. washingtonensis<i/> and <i>Megastigmus spermotrophus</i>. Although statistically significant differences in percentage of damaged seeds were detected among clones, these differences were not great enough to be of practical importance