Impact of sublethal doses of Piper guineense (Schum and Thonn) on the biological parameters of Callosobruchus maculatus (F.) (Coleoptera: Chrysomelidae) reared on different cowpea varieties

Cowpea varieties show a wide range of characteristics in their composition that can determine Callosobruchus maculatus (Fabricius) response and survival. Consequently, this work investigated the influence of sublethal doses of Piper guineense on C. maculatus raised on four cowpea varieties: ART-98–12, Niger White, Oloyin, and Ife Brown. Our results demonstrated that C. maculatus from different varieties, despite being reared under the same conditions, responded differently to sublethal doses of P. guineense. Cowpea beetles from ART-98–12 were the most susceptible while those reared on Ife Brown were the least susceptible. Across varieties, survival and reproductive parameters of C. maculatus differed. Furthermore, the ranking for the percentage reduction in the number of eggs laid by C. maculatus was ART-98–12 > Niger White > Oloyin > Ife Brown. According to the log-rank statistic test, the difference observed in C. maculatus’ survival can be explained by variety (log-rank statistic: χ2 [df = 3, N = 16] = 15, p = 0.004). Conversely, the survivability of the chrysomelid beetles reared on Niger white was significantly lower (p = 0.012) compared to the other varieties. This study highlights the role of cowpea variety in dictating the efficacy of a given botanical against C. maculatus.