ARS | Publication request: Residual efficacy of methoprene for control of Tribolium castaneum (Coleoptera: Tenebrionidae) larvae at different temperatures on varnished wood, concrete, and wheat

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 10, 2012
Publication Date: February 1, 2012
Citation: Wijayaratne, L., Fields, P.G., Arthur, F.H. 2012. Residual efficacy of methoprene for control of Tribolium castaneum (Coleoptera: Tenebrionidae) larvae at different temperatures on varnished wood, concrete, and wheat. Journal of Economic Entomology. 105(2): 718-725. http://dx.doi.org/10.1603/EC11375.

Interpretive Summary: The insecticide methoprene is an insect growth regulator that affects molting and development of immature insects. It has been evaluated as an aerosol insecticide but it has not been sufficiently examined as a residual surface treatment. We conducted studies by spraying concrete and wood surfaces with methoprene, exposed larvae of the red flour beetle on the treated surfaces, held these surfaces at different temperatures, and recorded adult emergence. We also conducted studies by treating concrete and wheat with methoprene and holding the wheat at high temperatures. Methoprene applied to wood gave excellent residual control of the red flour beetle, but, on concrete, residual control declined with time and the presence of flour on concrete reduced the effectiveness of the insecticide. Methoprene was also stable on concrete and wheat at high temperatures. Persons responsible for insect pest control can utilize these results to integrate methoprene into their management programs for the red flour beetle.

Technical Abstract: The residual efficacy of the juvenile hormone analogue, methoprene (Diacon II), was evaluated in bioassays using larvae of Tribolium castaneum (Herbst) exposed on varnished wood or unsealed concrete treated with a liquid formulation and held at different temperatures. When these surfaces were stored at 20, 30 or 35ºC for 0-24 weeks, percentage adult emergence on concrete increased with time. In contrast, there was no adult emergence from larvae exposed to varnished wood at 24 weeks following treatment at any of these temperatures. The presence of flour reduced residual efficacy of methoprene on concrete, but not on varnished wood, with no differences between cleaning frequencies. Methoprene was also stable for 48 h on concrete held at 65°C and wheat held at 46°C. Results show that methoprene is stable at a range of temperatures commonly encountered in indoor food storage facilities, and at high temperatures attained during insecticidal heat treatments of structures. The residual persistence of methoprene applied to different surface substrates may be affected more by the substrate than by temperature.