The study was conducted to investigate the combined effects of various plant powders and Silico-sec, a diatomaceous earth, on Callosobruchus maculatus at the research laboratory of the Department of Crop Pest and Soil Management, the Federal University of Technology, Akure. The study included three replications. The treatments consisted of three (3) plant materials derived from the dry flower buds of Eugenia aromatica, seeds of Piper guineense, and leaves of Nicotiana tabacum and their combination with Silico-sec. In one experiment, 0.4g of each plant material was added to 20 C. maculatus adults (10 couples, aged 1-2 days) in 20g of Ife Brown cowpea seeds, all contained within an air-tight plastic container. Another experiment involved the addition of 0.4g mixtures of Silico-sec and each plant powder (E. aromatica, P. guineense, and N. tabacum) in various ratios (1:5, 5:1, 1:10, 10:1, and 1:1) to the same number of C. maculatus adults in 20g of cowpea seeds, also in separate air-tight plastic containers. All the treatments and their combination were laid out in a completely randomized design (CRD) repeated three times. Data were collected at 12, 24, and 48 at p,0hours post-treatment. Oviposition, adult emergence, and seed weight loss were evaluated. The results demonstrated that both the plant powders and Silico-sec were effective in controlling C. maculatus infestation on cowpea by causing significant adult mortality at p< 0.05, reducing oviposition, suppressing F1 adult emergence, and minimizing seed damage. Among single applications, Silico-sec and E. aromatica powder provided the best protection for stored cowpea, yielding the highest adult mortality, lowest oviposition, most suppressed F1 adult emergence, and minimal seed damage. However, the mixture of Silico-sec and P. guineense at ratios of 5:1 and 10:1 offered the best protection, exhibiting significantly higher mortality, lower oviposition rates, suppressed F1 adult emergence, and reduced seed damage compared to other treatments. This study suggests that combination of P. guineense and Silico-sec is particularly effective in controlling cowpea storage pests and could serve as a viable alternative to synthetic insecticides for protecting stored cowpea against C. maculatus.
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