Abstract: In pest management programs, the control of pests in structural facilities or sites, where processed food products are consumed or stored, requires the application of insecticides upon a variety of substrate surfaces. In order to determine the insecticidal effectiveness on different substrate surfaces, adults of the cowpea weevil, Callosobruchus maculatus (F.), were exposed to field recommended concentrations of chlorpyrifos, abamectin and deltamethrin insecticides. The results showed that abamectin caused mortality rates of 63.33%, 22.41%, 12.9% and 11.9% while deltamethrin caused mortality rates of 55%, 44.2%, 41.3% and 37.4% on glass, ceramic tile, plastic and paper disc surfaces, respectively. Exposures to chlorpyrifos led to 100% mortality in all surfaces. Probit analysis of data showed that LC₅₀ values were 8.66, 13.6, 29.16 and 56.5 μg/mL for chlorpyrifos, 119.4, 446.2, 774.2 and 836.4 μg/mL for abamectin, and 1 008, 1 131, 1 210 and 1 336 μg/mL for deltamethrin on the glass, ceramic tile, plastic and paper disc surfaces, respectively, based on formulated materials. It is concluded that chlorpyrifos is the most toxic insecticide to the cowpea weevil, but that its toxicity was reduced in the glass, ceramic tile, plastic and paper disc surfaces in sequence.

Key words: Callosobruchus maculatus, lethal effects, abamectin, deltamethrin, chlorpyrifos