Evaluating the Effect of Cowpea Variety on the Insecticidal Response and Antioxidant Enzymes of Callosobruchus Maculatus (Fabricius) Treated with Two Plant Powders

Abstract

Callosobruchus maculatus (Fabricius), a notorious pest wreaking havoc during the storage phase of cowpea, has remained a serious menace militating against cowpea production in sub-Saharan Africa for years. This study investigated the effects of cowpea varieties [Gombe (GBV) and Sokoto (SKV)] on the insecticidal response and antioxidant enzymes of adult C. maculatus treated with powders of Piper guineense (Schum and Thonn) and Syzygium aromaticum (L.). The study was conducted at an ambient temperature (28 ± 3ºC) and relative humidity (75 ± 6). Bruchids were exposed to dosages ranging from 0.05 to 0.55 g/20 g cowpea. The morphometrics of the cowpea seeds and emerged bruchids were also subjectively determined. GBV generally had significantly longer, wider, and thicker seeds than SKV. Similarly, GBV-reared bruchids were significantly (P 0.001) wider and longer in body size than SKV-reared bruchids. Regardless of cowpea variety, S. aromaticum was generally more toxic to the bruchids than P. guineense. GBV-reared bruchids were more susceptible to both plant powders than SKV-reared bruchids. The specific activities of Superoxide Dismutase, Catalase, and Glutathione also varied with cowpea varieties and plant powders. Cowpea variety, experimental dosage, and their interaction (V*D) significantly (P 0.001) influenced the specific activities of the three enzymes. Hence, the two plant powders, especially S. aromaticum, could be used as effective protectants of cowpea seeds against C. maculatus infestation. The findings in this study could ultimately contribute to ensuring the security and integrity of cowpea seeds, sustaining them as a staple food crop.