02334nas a2200157 4500008004100000245016700041210006900208300001400277490000800291520169400299653001201993100002202005700001902027700002002046856011002066 1983 eng d00aLaboratory Evaluation of Microencapsulated Formulations of Chlorpyrifos-Methyl Against Black Fly Larvae (Diptera: Simuliidae) and Selected Nontarget Invertebrates0 aLaboratory Evaluation of Microencapsulated Formulations of Chlor a1189-12010 v1153 a

Laboratory tests were conducted under simulated stream conditions to determine the efficacies of microencapsulated formulations of chlorpyrifos-methyl (Reldan® 10–10) against Simulium and Prosimulium late-instar larvae. In tests with eight formulations, no correlation was evident between efficacy and formulation stability (i.e., cross-linking ratio). The most effective formulations were 34-75-50A, 119-75-6A, and 119-75-6C. The LC50 and LC90 values of 34–75–50A against S. vittatum were 5.5 μg/L and 24 μg/L/10 min. respectively. The formulations 119-75-6A and 119-75-6C were statistically not different from 34-75-50A. Prosimulium magnum was less susceptible (LC50 = 36μg/L, LC90 = 205 μg/L). Susceptibility among S. vittatum larvae varied inversely with size. Treatment with formulation 34-75-50A at 237 μg/L/10 min (the observed LC100 for S. vittatum) severely affected nymphs of the mayfly Baetis sp. and the stonefly Taeniopteryx burksi, but had a minimal effect on most other detritivores, filter-feeding caddisflies (Hydropsyche betteni and Brachycentrus sp.), and predators. Mortality increased significantly in some of these latter species, however, when exposed to 492 μg/L/10 min (the observed LC100 for P. magnum). Tests indicated that there was some leakage of active ingredient from the microcapsules into the water. Although the microencapsulated formulations of chlorpyrifos-methyl were designed to have selective toxicity to black fly larvae, our laboratory tests indicated that they were not as safe towards nonfilter feeders as had been expected.

10abiology1 aRodrigues, C., S.1 aMolloy, D., P.1 aKaushik, N., K. uhttp://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=8550864&fileId=S0008347X00035434