Investigating insecticidal and repellent activity of Momordica charantia, Calotropis gigantea and Cordia curassavica against Oebalus poecilus

Abstract

Oebalus poecilus (paddy bug) is a destructive rice pest in Guyana that is currently controlled with synthetic chemical pesticides. Increasing resistance rates and farmer's overuse of pesticides have resulted in economic and ecological issues for Guyanese rice farmers. Amid growing economic and ecological concerns, this experiment aimed to investigate the use of alternative botanical extracts from the leaves of Momordica charantia (Baan-Carailli), Calotropis gigantea (Madar-Flower) and Cordia curassavica (Blacksage) to control paddy bug infestation by testing their efficacy as insecticides on O. poecilus. A completely randomized experimental design and a hot water extraction method was used to prepare the leaf extracts used in this experiment. Three different concentrations (6%, 12% and 24%) of each extract were tested on the adult stage of the bugs for mortality and repellent activity. The results, after 72 hours, were recorded and revealed that all extracts demonstrated insecticidal properties. No toxicity as a systemic insecticide on contact with bugs was observed, thus implying no repellent effect. At 72 hours, the average mortalities recorded for the different extracts were Momordica charantia (98.62%), Cordia curassavica (90.25%) and Calotropis gigantea (100%). Extracts performed better at 6% and 24% when compared. Leaf extracts from Calotropis gigantea at 6% and 24% were most effective when compared to the other extracts used in this experiment.