- Varty, I. W.
Committee for Environmental Monitoring of Forest Insect Control Operations
This multiple author report describes ecological effects and insecticide persistence from an aerial spray program in New Brunswick, 1977, for 4,166,605 ac (1,686,201 ha) of budworm-infested fir-spruce forest.
The operational insecticides were formulations of fenitrothion, aminocarb and trichlorfon, while phosphamidon was used experimentally. The surveillance program incorporated 34 studies on songbirds, rodents, salmonids, stream organisms, pollinating insects, arboreal and ground predators, budworm parasitoids, and divers aspects of insecticide persistence in various tissues and habitats.
Most of the faunal studies were based on assessments of field population density. The insecticide regimes had little, if any, lethal effect on birds and fish. A mild increase in live and dead drift of stream benthos sometimes followed fenitrothion and trichlorfon usage, but not aminocarb usage. Methods of estimating wild bee populations in spray blocks were tested. Aminocarb treatment did not appear to be detrimental to wild bees or honey bees, but a long history of fenitrothion usage was reflected in lower abundance of some bumble bee species, and in lower pollination success. Wild bee abundance in blueberry fields appears to have fully recovered w¡thin 3 years of population reduction associated with fenitrothion drift from spray blocks. Parasitism in spruce budworm and the abundance of predators on firs do not appear to be much influenced by perennial fenitrothion usage. In contrast with fenitrothion, use of amino- carb produced heavy knockdown of spiders.
Residues of fenitrothion on fir foliage may persist for a year but do not constitute a chronic hazard to browsing deer. The discovery of trace quantities of fenitrothion in estuarine shellfish remote from spray blocks indicates rapid mobility of the insecticide over at least 30 km. New knowledge of the persistence and chemistry of fenitrothion in stream water was gained. Techniques for the preservation of aminocarb and fenitrothion in water samples were tested. Methods of measuring the distribution of insecticides in air and on foliage were investigated.
The impact of these insecticides in an ecological context is summarized and is considered tolerable in forest and stream ecosystems. Ten proposals for better surveillance and safer spraying were recommended.