%0 Journal Article
%T Evaluation of pyrethroids toxicity in a laboratory strain and a fi eld population of Rachiplusia nu (Lepidoptera: Noctuidae) using two bioassay techniques Evaluaci車n de la toxicidad de piretroides en una cepa de laboratorio y una poblaci車n de campo de Rachiplusia nu (Lepidoptera: Noctuidae) usando dos m谷todos de bioensayo
%A Romina Russo
%A Juan C. Gamundi
%A Ra迆l A. Alzogaray
%J Revista de la Sociedad Entomolˋ3gica Argentina
%D 2012
%I Sociedad Entomol車gica Argentina
%X Soybean is the most important crop in Argentina and Rachiplusia nu (Guene谷) (Lepidoptera: Noctuidae) is one of its main pests. In this study, the toxicity of five pyrethroids applied topically and by exposure to films on filter paper was evaluated on third instar larvae from a laboratory strain and a field population of R. nu. Four cyanopyrethroids and one non-cyanopyrethroid (permethrin) were tested. All cyanopyrethroids showed the same order of increasing toxicity, regardless of the form of application and origin of the larvae: cypermethrin < ?-cyhalothrin < deltamethrin <  -cyfluthrin. Knock down Dose 50% and Knock down Time 50% values increased as a function of the solubility of cyanopyrethroids in water. Permethrin showed a different behavior: it was the most toxic insecticide for the laboratory strain when applied topically, but the least toxic when larvae were exposed to filter papers. In general, the pyrethroids were more toxic for laboratory larvae than for the field ones. After calculating Resistance Factor (RF) values, low-moderate resistance to permethrin, cypermethrin and ?-cyhalothrin was observed in the experiments with topical application. However, exposure to films on filter papers failed to detect resistance. There was not correlation between the RF values obtained by both methods. These results suggest that the population of R. nu studied here has low-moderate resistance to some pyrethroids, and that topical application is a more appropriate method for quantifying resistance than exposure to insecticide films on filter paper. La soja es el cultivo m芍s importante en la Rep迆blica Argentina y Rachiplusia nu (Guene谷) (Lepidoptera: Noctuidae), una de sus principales plagas. En este estudio se evalu車 la toxicidad de cuatro cianopiretroides y un no-cianopiretroide, aplicados en forma t車pica o por exposici車n a filmes sobre papeles de filtro, en ninfas del tercer estadio de una cepa de laboratorio y una poblaci車n de campo de R. nu. Todos los cianopiretroides mostraron el mismo orden de toxicidad creciente, independientemente de la forma de aplicaci車n y del origen de las larvas: cipermetrina < ?-cihalotrina < deltametrina <  -ciflutrina. Los valores de Dosis de Volteo para el 50% (DV50) y de Tiempo de Volteo para el 50% (TV50) aumentaron en funci車n de la solubilidad de los cianopiretroides en agua. El no-cianopiretroide permetrina mostr車 un comportamiento diferente: fue el insecticida m芍s t車xico para la cepa de laboratorio cuando se hizo una aplicaci車n t車pica, pero el menos t車xico cuando las larvas fueron expuestas a filmes sobre papeles de fil
%K Oruga medidora
%K Plagas de la soja
%K Resistencia a insecticidas
%K Soybean looper
%K Soybean pests
%K Insecticide resistance
%U http://www.scielo.org.ar/scielo.php?script=sci_arttext&pid=S0373-56802012000100011