AN ASSESSMENT OF THE IMPACT OF LARGE SCALE SPRAYING OPERATIONS ON THE REGIONAL DYNAMICS OF SPRUCE BUDWORM (LEPIDOPTERA: TORTRICIDAE) POPULATIONS

Abstract

AbstractExploratory data analysis was employed to investigate the regional dynamics of managed budworm populations based upon survey data reporting spruce budworm egg-mass densities and damage to balsam fir. The Maine Forest Service collected these data annually from 1975 to 1980 at approximately 1000 different locations each year throughout Maine's spruce–fir forest regions. Although spraying was often associated with ‘better’ conditions in heavily defoliated or infested areas, it was generally associated with somewhat ‘poorer’ conditions in areas which had experienced only light defoliation or infestation in the previous year. The analysis also indicated that while insecticide application may reduce budworm larval populations immediately after application, the largest relative decrease in defoliation rates appeared the year after insecticide application. Insecticide treatments were not as effective as expected. In the year following application, the maximum reduction observed in average defoliation was 20% and in average egg-mass density the maximum reduction was 50%. In many cases the reduction was substantially less. Spraying was not associated with any substantial decline in hazard rating.