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Abstract

The present study aimed to evaluate the insecticidal efficacy of alkaloid extracts from Duranta repens fruits at concentrations of 4%, 6%, and 8% against different developmental stages of the southern cowpea beetle ( Callosobruchus maculatus ) under laboratory conditions. The tested stages included eggs, last instar larvae, and pupae at 24 and 120 h of age. The 8% alkaloid extract exhibited the highest ovicidal activity, achieving 100% egg mortality, compared to 60% mortality at the 4% concentration. Similarly, the 8% concentration induced the highest larval mortality (82%) in the last instar stage, significantly outperforming the lower concentrations. Pupae treated at 24 h old with the 8% extract recorded a 93% mortality rate, while 120-h-old pupae showed a reduced mortality rate of 77% at the same concentration. In contrast, the 4% extract resulted in 68% and 60% mortality for 24- and 120-h-old pupae, respectively. Furthermore, the 8% alkaloid extract was most effective in protecting stored cowpea seeds, recording the lowest seed loss (6.55%) after six months of storage, compared to the 4% and 6% treatments. The study also demonstrated that seed germination was not adversely affected by any treatment across all evaluation periods (1 day, 90 days, and 180 days). Overall, the 8% alkaloid extract of D. repens fruits proved to be the most effective concentration in controlling C. maculatus and preserving seed viability during storage.