THE SPRUCE BUDWORM IN CANADA AND THE US

Since the early 1950s the spruce budworm (Choristoneura fumiferana) has posed a serious threat in parts of eastern Canada, particularly New Brunswick, (Eidt, 1975, 1977; Symons, 1977a) and adjacent states of the US (Nash, Peterson & Chansler, 1971). In order to protect the valuable timber trees against defoliation, the method of control originally adopted was aerial spraying with DDT, which was practised from 1952 onwards. Since that time the intensity and extent of the infestation has increased. In New Brunswick for example, between 1952 and 1957 the sprayed area increased from 75 × 103 ha to 2.3 × 106 ha (8876 sq. miles). Many of the areas treated twice a year recorded a total application of 560 g/ha DDT per annum, and it was after such heavy treatment that Atlantic salmon, living in streams and rivers in the sprayed forest area, were found to be severely affected.

DDT began to be phased out in 1968, and by 19 70 was replaced completely by organophosphorus compounds, mainly fenitrothion. By 1976 the sprayed area in New Brunswick had increased to 4.0 × 106 ha (15000 sq. miles). By that year infestation had extended to other provinces, Quebec, Ontario and parts of Newfoundland and Nova Scotia up to a total area of 30 × 106 ha.

Fenitrothion continues to be the insecticide of choice, in Canada, and at the time of writing appears unlikely to be superseded by other insecticides (D. C. Eidt, personal communication).