Etofenprox as grain protectant for the management of five key stored-product insect pests

Abstract

Etofenprox is a broad spectrum pyrethroid insecticide with low toxicity to mammals, fishes, and honeybees. In the present study it was evaluated as grain protectant against Ephestia kuehniella (Lepidoptera: Pyralidae) larvae, Prostephanus truncatus (Coleoptera: Bostrychidae) adults, Rhyzopertha dominica (Coleoptera: Bostrychidae) adults, Sitophilus oryzae (Coleoptera: Curculionidae) adults, and Tribolium confusum (Coleoptera: Tenebrionidae) larvae and adults. Etofenprox was applied at 0.1, 1, 5, and 10 ppm on wheat, or maize in the case of P. truncatus, and tested at different combinations of temperatures (20, 25, and 30 °C) and relative humidity (RH) levels (55 and 75%). Progeny production of the tested coleopteran adult species was also assessed. For E. kuehniella, after 21 days of exposure 75.6% of the exposed larvae were killed at 20 and 30 °C/55% RH. Mortality of P. truncatus adults reached 99.4 and 97.8% at 10 ppm of 55 and 75% RH, respectively, at 30 °C. For S. oryzae, after 21 days of exposure, mortality was moderate at both RH levels, even at the elevate doses, reaching 66.7% at 10 ppm at 20°C/75% RH. All R. dominica adults died 21 days post-exposure at 30°C/55% RH and 25 or 30°C/75% RH at 10 ppm. For T. confusum adults, mortality was 81.1% 10 ppm 21 days post-exposure at 20°C/75% RH. Etofenprox killed 99.4% of the exposed T. confusum larvae at 10 ppm respectively 14 days post-exposure at 25°C/55% RH. Concerning progeny production, complete suppression was recorded for P. truncatus, R. dominica, and T. confusum in various combinations of temperature/RH. Our findings indicate that etofenprox is a well-promising insecticide for the protection of stored grains. However, its performance differs among insect species and abiotic conditions.

Keywords: Coleoptera; Lepidoptera; Pyrethroid insecticide; Relative humidity; Temperature.