Published online by Cambridge University Press: 31 May 2012
Neodiprion swainei Middleton is the most serious defoliator of jack pine, Pinus bamksiana Lambert, in Canada. The damage to stands of this species in northern Quebec has been extensive and has resulted in considerable forest-fire hazard. Virus infected sawflies were found in the Lac Gagnon area in Quebec in 1956, and a study of the disease was begun by the Quebec Laboratory in 1957. Laboratory propagation methods were developed and resulted in the production of a quantity of polyhedral concentrate of a virulent strain. Concentrations of polyhedral bodies needed in a spray formulation to infect and kill larvae of various ages were determined in the laboratory and field tests demonstrated the potentialities of this disease as a biological control agent (Smirnoff 1960b, 1961a). These studies served as a basis for the experiment in the dissemination of the disease by aircraft described in this paper.