Systematic differences in the population density of green spruce aphid, Elatobium abietinum in a provenance trial of Sitka spruce, Picea sitchensis

SUMMARY Aphid populations were evaluated on foliage samples within an experimental forest area. There were marked differences in aphid density between three areas within the experiment and between individual trees. Significant differences between provenances of Sitka spruce were of particular interest since aphid density appeared to be related to the latitudinal origin of the seed. The more southerly provenances were especially susceptible. The accumulated evidence suggests that no single physiological difference between trees will account for all observed variations in aphid density although the later growth cessation of susceptible provenances deserves further study.