Efficacy of various natural plant extracts and the synthetic insecticide cypermethrin 25EC against Leucinodes orbonalis and their impact on natural enemies in brinjal crop

Abstract

The fruit and shoot borer, Leucinodes orbonalis, is a major pest affecting brinjal production throughout the world. In this study, we investigated the efficacy of various natural plant extracts and a synthetic insecticide against L. orbonalis, and their impact on natural enemies. Eight different treatments were tested as follow: (1) neem oil at 2%, (2) neem oil at 5%, (3) Eucalyptus leaf extracts at 3%, (4) Eucalyptus leaf extracts at 6%, (5) garlic bulb extracts at 4%, (6) garlic bulb extracts at 8%, (7) cypermethrin 25 EC, and (8) untreated control. Results showed the lowest shoot and fruit infestation in cypermethrin-treated plots (2.03%), followed by neem oil (5%). The highest shoot and fruit infestation were recorded in the untreated control, followed by garlic bulb extract (4%). The highest number of flowers per plant was observed in cypermethrin-treated plots, followed by neem oil (5%), while the lowest was recorded in untreated control, followed by garlic bulb extract (4%). The highest population densities of ladybird beetle, green lacewing, and syrphid fly were recorded in the control, while the lowest densities of these natural enemies were observed in cypermethrin-treated plots. The highest yield of brinjal was recorded in cypermethrin-treated plots (3731.5 kg/ha), followed by neem oil at 5% with 3273.2 kg/ha, while the lowest yield was obtained in control plots (753.3 kg/ha). Overall, this study showed that the natural plant extracts (notably neem oil 5%) significantly reduced shoots and fruit infestation, and could, therefore, be used against L. orbonalis in the brinjal crop.