Brain cholinesterase inhibition in forest passerines exposed to experimental aminocarb spraying.

Abstract

Continued spruce budworm (Choristoneura fumiferana) infestation of the fir-spruce forest of eastern Canada has been marked by a constant search for control strategies that are effective, environmentally acceptable, and that pose no threat to human health. In New Brunswick, forest protection has relied heavily on the use of chemical insecticides for almost three decades, a practice for which there is apparently no viable alternative at present. Testing of the efficacy and safety of new chemicals, old chemicals in new formulations, and of developments in spraying technology have been important elements in the province's approach to management of the budworm problem. This study was carried out in the context of a series of spray trials of a new formulation of aminocarb (4-(dimethylamino)-3-methylphenol methylcarbamate) known as Matacil R 180 Flowable (180F), conducted by the Forest Pest Management Institute, Canadian Forestry Service, primarily to determine efficacy against spruce budworm. The trials were of particular interest to the Canadian Wildlife Service since there is little published information on the effects of aminocarb on brain cholinesterase (ChE) activity in forest songbirds and the logistical problems normally encountered in monitoring bird responses under operational spraying Conditions were minimized by the relatively small scale of the project. MATERIALS AND M~THODS Spray PlOts were located in predominantly fir-spruce forest about 25 km west of Bathurst, in northern New Brunswick. Each was 50 ha (I.0 km x 0.5 km) in area, and was sprayed by a Cessna 188 Ag-Truck fitted with four Micronair AU3000 rotary atomizers. The two plots of interest to us were both sprayed at a stated emission dosage of 70 g/ha of active ingredient. By volume, the formulation consisted of 25.93% Mataci~ 180F, 1.27% AtloxR(emulsifier), 72.27% water (carrier) and 0.53% Rhodamine Red dye. The emulsion was emitted at a rate of 1.5 L/ha. Droplet VMD and NMD at first