Insecticidal activity of Vitex cymosa (Lamiaceae) and Eschweilera pedicellata (Lecythidaceae) extracts against Sitophilus zeamais adults (Curculionidae)

This study evaluated insecticidal and repellent effects of Vitex cymosa and Eschweilera pedicellata extracts against Sitophilus zeamais adults. Contact on filter paper discs and contaminated grain ingestion assays were performed. The repellent effect was evaluated with the “preferential area” method. The extracts provided good results by ingestion and as repellents, but not by contact. V. cymosa branches methanol extract was the best, killing nearly 70% of the individuals at its highest concentration, followed by V. cymosa flowers dichloromethane extract and E. pedicellata branches aqueous extract. Among these, only V. cymosa leaves dichloromethane extract did not reduce the number of individuals in F1. Analyzing the repellent effect, when the variable concentration was taken into account, no extract was dose-dependent, and the intensity of response varied with the time interval. Among the extracts tested, V. cymosa branches methanol extract is the most promising one, which negative effect on parental resulted in F1 decrease number and the ingestion way was the most efficient.