RESUMO
Insecticidal dipping fluid emulsions, mixed in vitro in dam water containing suspended clay particles and 1% w/v zinc sulphate, were analysed to determine rates of settling of diazinon, cyhalothrin and cypermethrin. Fifteen minutes after mixing, the concentration of the insecticides 5 cm below the surface had declined by 72.5%, 72.8% and 89.4%, respectively. On remixing, the concentration of insecticide in suspension was close to or greater than the initial concentration. In 2 trials, lice were eradicated from sheep showered with dip wash mixed in cloudy dam water to which 1% w/v of zinc sulphate was added. In 12 flock treatments in which 1000 to 2000 sheep were dipped with added zinc sulphate, the concentration of insecticide remained above the minimum lethal for susceptible strains of lice. However, lice were still present 6 months later in 8 of these flocks. When zinc sulphate is added to dip wash, agitation is needed to maintain the insecticide in suspension.
Assuntos
Inseticidas/uso terapêutico , Infestações por Piolhos/veterinária , Doenças dos Ovinos/tratamento farmacológico , Sulfato de Zinco , Animais , Diazinon/administração & dosagem , Diazinon/normas , Diazinon/uso terapêutico , Relação Dose-Resposta a Droga , Inseticidas/administração & dosagem , Inseticidas/normas , Infestações por Piolhos/tratamento farmacológico , Nitrilas , Piretrinas/administração & dosagem , Piretrinas/normas , Piretrinas/uso terapêutico , Ovinos , SuspensõesRESUMO
Acid hydrolysis is a means of disposal of diazinon, O,O-diethyl-O-(2-isopropyl-4-methyl-6-pyrimidinyl)-phosphorothioate. Procedures were developed for the hydrolysis of three military standard diazinon formulations (47.5% emulsifiable concentrate, 2% dust and 0.5% oil solution). The kinetics of hydrolysis at four temperatures were obtained for each formulation in order to predict the half-life of diazinon between 5 degrees and 50 degrees C. The toxicities of the reaction mixtures were evaluated by aquatic bioassay with bluegill sunfish (Lepomis macrochirus). When the hydrolysis of a formulation had reduced the diazinon concentration by greater than 99.9%, there was less than 50% reduction in the toxicity of the reaction mixture to bluegill sunfish. Analysis of reaction mixtures showed that the toxic component was O,O,O,O-tetraethyldithiopyrophosphate (Sulfotepp), which was present in all diazinon formulations.
