- Canadian Forestry Service
The persistence and distribution of four insecticides (fenitrothion, trichlorfon, aminocarb, and phosphamidon) and the ecological consequences of their use were monitored in the 10-million-acre aerial spray program against spruce budworm in New Brunswick in 1976. The population responses of various faunal groups were measured by extensive field surveys.
Birds: Spray operations were characterized by an uneven distribution of toxic effects on songbirds. Warblers and kinglets were especially vulnerable to phosphamidon, and a reduction in numbers sometimes occurred after application of fenitrothion. The type of spray aircraft and delivery system had a significant influence on the hazard to songbirds.
Mammals: Fenitrothion and phosphamidon had no deleterious influence on the fertility of voles and deermice, indicating little hazard to these small mammals. There were no cases of poisoning of livestock or game mammals attributable to the sprays.
Stream fauna: The impact on aquatic insects was highly variable. Aminocarb and trichlorfon apparently had little effect, as assessed from survival of bottom-dwelling insects and from drift of dead insects. Mortality associated with the highest prescribed dosage of fenitrothion ranged from none to very heavy. No direct effect on fish was observed.
Pollinators: Insecticide drift into blueberry fields from nearby forest spray zones ranged from none to heavy. Wild bee abundance was not substantially changed by light deposits. Experience with heavy deposits of fenitrothion indicated population recover in 1-4 years.
Biological control agents: Large-scale, recurrent applications of fenitrothion in the 1970s do not appear to have eroded the effectiveness of biological control by parasites and predators, nor to have triggered irruptions of non-target pests.
Insecticide distribution and persistence: The deposit of insecticide from a given emission rate varied from place to place by a factor of 10. Double swathing within the spray block and drift into farmland sometimes occurred. Local contamination by accidental spillage was minor. Experimental use of tracer dyes showed wide variation in deposit, even within a small group of trees. The persistence of some of the insecticides in the forest environment was found to be brief.
In the long term, the monitoring agencies are looking for symptoms of ecosystem disturbance and associated degradation of resource productivity, with the aim of modifying protection tactics that are deleterious. They face acute sampling problems because of the size of operations and of the variability of spray regimes, deposition patterns, and animal abundance. It is recommended that the monitoring and research effort be expanded, that liaison with spray agencies be closer, and that certain treatment dosages be used cautiously.