AERIAL APPLICATION OF INSECTICIDES AND THE SUPPRESSION OF INCIPIENT SPRUCE BUDWORM OUTBREAKS

Abstract

The aerial application of insecticides against spruce budworm outbreaks is now a common practice. The measure had always been applied in outbreaks covering more or less extensive areas until 1960 when an opportunity was provided of spraying a small incipient infestation in the Lower St. Lawrence region of the Province of Quebec. It was hoped that early treatment might suppress the infestation and prevent its spread. Although the operation was successful in greatly reducing insect numbers in the area treated, it failed to arrest the infestation. Wind dispersal of first- and second-instar larvae prior to spray application resulted in the spread of the infestation beyond the area delimited for treatment. Also, the warm and dry weather in the spring of 1960, and the abundance of staminate flowers on the balsam fir and spruce trees greatly favoured larval survival. The aerial application of insecticides as a method of suppressing incipient spruce budworm outbreaks is discussed in the light of these results.