Abstract. Laboratory dose-response studies were conducted with four species of adult bees, Apis mellifera (workers), Andrena erythronii (females), Megachile rotundata (females), and Bombus terricola (workers), using six insecticides, permethrin, mexacarbate, aminocarb, fenitrothion, carbaryl, and trichlorfon. All insecticides were applied topically to the thorax of the bees as technical grade in an acetone carrier. Mortality was accumulated over 48 h, and probit analyses were conducted separately on data sets expressed in units of IxgAI (active ingredient)/g body weight and of p~gAI/bee. LDso values with 95% confidence limits and slopes with standard errors are provided for each bee/insecticide combination in each data set. Relative toxicities, relative susceptibilities, and fresh body weights are also provided. The analysis in units of p~gAI/g body weight indicated that the insecticides were typically ranked in order of decreasing toxicity--permethrin, mexacarbate, aminocarb, fenitrothion, carbaryl, and trichlorfon. Likewise, the bees ranked from the most to least susceptible in the order ofA. mellifera, A. erythronii, M. rotundata, andB. terricola. Trends within the data set for units of IxgAl/bee were less consistent. These data are discussed and compared with other published data on the toxicology of insecticides to bees and from the perspective of risk assessment.
The effects of permethrin on native and caged fish when aerially applied directly to forest streams at dosages between 8.8 and 70 g ha−1 were studied between 1976 and 1981. None of the applications caused mortality of caged or native fish in streams. Trout and salmon diets were altered by the treatments due to effects on fish food organisms. The duration of the effects varied from several months to over a year with increasing dosage. Reductions in salmonid growth rates and reductions in fish densities in treated areas, presumably due to emigration, were documented following severe impacts on aquatic invertebrates in salmon nursery streams. Growth rates and population densities both recovered within four months after treatment.
A series of experiments was conducted between 1977 and 1981 to evaluate the effects of aerially applied permethrin on forest stream invertebrates. All permethrin applications to forest streams resulted in large drift increases, and most produced measurable reductions in benthos density. Recovery of benthic fauna following the various permethrin applications was apparent from 1 to 18 months post‐spray. In double‐application experiments, the second treatments reduced benthos density to a point at which recovery of numbers was slower than after the impact resulting from a single application of the same dosage.
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