Activity of two deltamethrin formulations on different surfaces against rice weevil, Sitophilus oryzae (L.)

Several methods are used to control stored product insects. The spraying of empty structures with insecticides, prior to the introduction of produce, is an important method for preventing development of insects. It is known that insecticide activity varies according to the various sprayed surfaces. In this study, the activity of deltamethrin was examined on concrete and plastic surfaces. Deltamethrin is a synthetic pyrethroid, active by contact against a variety of insects; applied in Israel in two formulations: KESHET 2.5% EC and BUNGY 1.5% SC (ADAMA Makhteshim Ltd.). Adults of the rice weevil, Sitophilus oryzae (L.), served as target insect in all experiments. The research was carried out in plastic Petri dishes and in Petri dishes with layer of concrete. Deltamethrin (KESHET 2.5% EC) was applied in water solution in doses of 0.02, 0.1, 0.5 g/m². Without concrete, complete mortality of S. oryzae was obtained at a concentration of 0.02 g/m², whereas in concrete plates, no mortality was found in all 3 concentrations. In contrast, deltamethrin (BUNGY 1.5% SC) in doses of 0.1 g/m², caused 100% mortality with and without concrete layer. The same results were found in the commercial warehouse. No difference in efficiency was found between the spraying methods: airbrush (Sparmax DH-125) or dripping by pipette. The results show that the efficacy of warehouse spraying by deltamethrin depends on its formulation.