INFLUENCE OF FOLIAR NITROGEN LEVELS ON SURVIVAL, DEVELOPMENT, AND REPRODUCTION OF WESTERN SPRUCE BUDWORM, CHORISTONEURA-OCCIDENTALIS (LEPIDOPTERA, TORTRICIDAE)

The influence of N levels in foliage of white-fir, Abies concolor, and Douglas-fir, Pseudotsugar menziesii, seedlings on various biological characteristics of the western spruce budworm, C. occidentalis Freeman, was studied. Seedlings were grown under greenhouse conditions and provided with nutrient solutions to maintain five foliar N levels ranging from 1.29 to 4.42% dry weight for white fir and 1.43 to 3.94% for Douglas fir. Larvae confined to treated seedlings were monitored through the next generation. Larval mortality was higher, and development time longer at both upper and lower extremes of foliar N than at midlevel. Mean pupal weight was significantly greater for larvae reared on white fir with the midrange foliar-N level. Mean number, and weight, of eggs laid were highest when larvae fed on foliage from the mid-range nitrogen level. Total number of larvae produced was lowest at the high and low extremes of foliar N levels.