Effect of temperature on two bio-insecticides for the control of confused flour beetle (Coleoptera: Tenebrionidae)
Keywords:
Tribolium confusum, Saccharopolyspora spinosa, Beauveria bassiana, climate change, stored product pestAbstract
Stored product pests account for as much as 10% of food loss worldwide. Insects such as the confused flour beetle, Tribolium confusum Jacquelin du Val (Coleoptera: Tenebrionidae), are major pests of small grain in storage bins and grain elevators in Montana. Cold winters and dry summers have traditionally helped reduce levels of T. confusum in storage bins. However, with change in winter temperatures, this pest has become harder to manage using physical measures such as desiccation. The alternative, the chemical insecticide aluminum phosphide, is effective at controlling T. confusum in grain stores but is highly toxic to mammals, and recently there has been development of resistance in grain pests. Newly approved biologically based insecticides can provide appreciable levels of control without the drawbacks of aluminum phosphide. In this study, we tested the short-term effectiveness of spinosad (extracts of Saccharopolyspora spinosa Mertz and Yao; Actinomycetales: Pseudonocardiaceae) and Beauveria bassiana (Bals.-Criv.) Vuill. (Hypocreales: Cordycipitaceae) (a fungus-based insecticide) for their effectiveness against T. confusum under various temperature regimes. Insects exposed to low temperature (8 °C) sustained high rates of mortality (about 80% for the control and both treatments). When held at 16 °C, mortality was low for both biologically based insecticide treatments and the control. At 22 °C, spinosad induced high mortality, whereas at 25 °C, B. bassiana induced mortality. Overall, our results indicate that temperature affected the effectiveness of these biologically based insecticides against the confused flour beetle and may be important when considering implementation of control programs in grain stores.
Resumen
Plagas de productos almacenados representan hasta el 10% de las pérdidas de alimentos en todo el mundo. Los insectos como el escarabajo confundido de la harina, Tribolium confusum Jacquelin du Val (Coleoptera: Tenebrionidae), es una de las principales plagas de granos pequeños en compartimentos de almacenamiento y elevadores de granos en Montana. Los inviernos fríos y veranos secos tradicionalmente han ayudado a reducir los niveles de T. confusum en compartimentos de almacenamiento. Sin embargo, con el cambio en las temperaturas invernales, esta plaga se ha vuelto más difícil de manejar utilizando las medidas físicas tales como la desecación. La alternativa, el insecticida químico fosfuro de aluminio, es eficaz en el control de T. confusum en granos almacenados, pero es altamente tóxico para los mamíferos, y recientemente se ha encontrado el desarrollo de resistencia en las plagas de granos. Insecticidas con base biológica recién aprobados pueden proveer un nivel apreciable de control sin los inconvenientes de fosfuro de aluminio. En este estudio, hemos probado la eficacia a corto plazo de spinosad (extractos de Saccharopolyspora spinosa Mertz y Yao; Actinomicetales: Pseudonocardiaceae) y Beauveria bassiana (Bals.-Criv.) Vuill. (Hypocreales: Cordycipitaceae) (un insecticida a base de hongos), por su eficacia contra T. confusum bajo diferentes regímenes de temperatura. Insectos expuestos a baja temperatura (8 °C) sostuvieron altas tasas de mortalidad (aproximadamente el 80% para el control y ambos tratamientos). Cuando fueron mantenidos a 16 °C, la mortalidad fue baja para ambos tratamientos insecticidas con base biológica y el control. A los 22 °C, spinosad indujo una mortalidad elevada, mientras que a 25 °C, B. bassiana indujo la mortalidad. En general, nuestros resultados indican que la temperatura afecta a la eficacia de estos insecticidas con base biológica contra el escarabajo confuso de la harina y puede ser importante cuando se considera la implementación de programas de control en granos almacenados
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