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Toxicity studies of so-called "inert" material with the bean weevil Acanthoscelides obtetus (Say)

By: Material type: ArticleArticleLanguage: English Description: 32(2):240-248Subject(s): LOC classification:
  • 4906
 In: Journal of Economic EntomologySummary: Se ensayo la accion de 6 polvos quimicamente inertes sobre Acanthoscelides obtectus. Todos los materiales se secaron previamente a 110 grados Centigrados. Los insectos se cubrieron completamente con el polvo, luego se liberaron sobre frijoles espolvoreados o no espolvoreados y se registraron los dias transcurridos hasta alcanzar un 50 por ciento de mortalidad. La mortalidad de los insectos tratados con alimento o sin el fue aproximadamente igual. La muerte del 50 por ciento se obtuvo en 0,5 dias (bentonita), 1,4 dias (carbonato de Mg), 1,9 dias (silice cristalino) 7,5 dias (silice amorfo), 7,4 dias (talco), 13,5 dias (polvo de cascara de nogal) y 13,2 dias para el testigo; sin embargo, la inclinacion de la curva de mortalidad del silice amorfo fue mayor que la del talco. Con respecto al silice cristalino, las particulas pequenas necesitaron 1,8 dias para matar el 50 por ciento de los gorgojos, mientras que las particulas gruesas necesitaron 14,5 dias (lo mismo que el testigo). Las particulas menores de 15 micro m son probablemente las activas. El autor explica este hecho en terminos de la mayor adhesion de las particulas pequenas al cuerpo. Parece que los insectos espolvoreados perdieron peso rapidamente, en especial durante los 2 primeros dias debido al efecto de los materiales inertes. No hubo variacion en el consumo de oxigeno entre los insectos tratados y no tratados. Por consiguiente se concluye que los materiales inertes actuan por desecacion. (CIAT)Summary: The action of 6 chemically "inert" dusts on Acanthoscelides obtectus were tested. All materials were previously dried 110 degrees Celsius. The insects were thoroughly covered by the dust, then released on dusted or nondusted beans, and days to 50 percent mortality recorded. Mortality of treated insects with or without food was nearly equal. Fifty percent kill was obtained in 0.5 days (bentonite), 1.4 (Mg carbonate), 1.9 days (crystalline silica), 7.5 days (amorphous silica), 7.4 days (talc), 13.5 days (wallnut shell flour) and 13.2 days for the control; however, the slope of the mortality curve for amorphous silica was much greater than for talc. As regards crystalline silica, the small particles required 1.8 days to kill 50 percent of the weevils, whereas the coarse particles took 14.5 days (the same as the control). Particles smaller than 15 micro are probably the active ones, the author explains this in terms of increased adhesion of the small particles to the body. It appeared that dusted insects lost weight rapidly, especially the 1st 2 days, because of the effect of the inert materials. The amount of oxygen consumption did not vary between treated and nontreated insects; it is therefore concluded that the inert materials act by desiccation. (CIAT)
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Se ensayo la accion de 6 polvos quimicamente inertes sobre Acanthoscelides obtectus. Todos los materiales se secaron previamente a 110 grados Centigrados. Los insectos se cubrieron completamente con el polvo, luego se liberaron sobre frijoles espolvoreados o no espolvoreados y se registraron los dias transcurridos hasta alcanzar un 50 por ciento de mortalidad. La mortalidad de los insectos tratados con alimento o sin el fue aproximadamente igual. La muerte del 50 por ciento se obtuvo en 0,5 dias (bentonita), 1,4 dias (carbonato de Mg), 1,9 dias (silice cristalino) 7,5 dias (silice amorfo), 7,4 dias (talco), 13,5 dias (polvo de cascara de nogal) y 13,2 dias para el testigo; sin embargo, la inclinacion de la curva de mortalidad del silice amorfo fue mayor que la del talco. Con respecto al silice cristalino, las particulas pequenas necesitaron 1,8 dias para matar el 50 por ciento de los gorgojos, mientras que las particulas gruesas necesitaron 14,5 dias (lo mismo que el testigo). Las particulas menores de 15 micro m son probablemente las activas. El autor explica este hecho en terminos de la mayor adhesion de las particulas pequenas al cuerpo. Parece que los insectos espolvoreados perdieron peso rapidamente, en especial durante los 2 primeros dias debido al efecto de los materiales inertes. No hubo variacion en el consumo de oxigeno entre los insectos tratados y no tratados. Por consiguiente se concluye que los materiales inertes actuan por desecacion. (CIAT) spa

The action of 6 chemically "inert" dusts on Acanthoscelides obtectus were tested. All materials were previously dried 110 degrees Celsius. The insects were thoroughly covered by the dust, then released on dusted or nondusted beans, and days to 50 percent mortality recorded. Mortality of treated insects with or without food was nearly equal. Fifty percent kill was obtained in 0.5 days (bentonite), 1.4 (Mg carbonate), 1.9 days (crystalline silica), 7.5 days (amorphous silica), 7.4 days (talc), 13.5 days (wallnut shell flour) and 13.2 days for the control; however, the slope of the mortality curve for amorphous silica was much greater than for talc. As regards crystalline silica, the small particles required 1.8 days to kill 50 percent of the weevils, whereas the coarse particles took 14.5 days (the same as the control). Particles smaller than 15 micro are probably the active ones, the author explains this in terms of increased adhesion of the small particles to the body. It appeared that dusted insects lost weight rapidly, especially the 1st 2 days, because of the effect of the inert materials. The amount of oxygen consumption did not vary between treated and nontreated insects; it is therefore concluded that the inert materials act by desiccation. (CIAT) eng

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