Insecticidal Efficacy of Azadirachta indica (A. Juss) and Ricinus cummunis (L.) Seed Oil Against Callosobruchus maculatus (F.) on Stored Mung Beans (Vigna radiata L. Wilczek)

Abstract

Stored pulses suffer from great damage and weight loss due to attack of Cowpea seed beetle Callosobruchus maculatus (Fabricius) (Coleoptera: Chrysomelidae), thus, it was important to handle the pest infestation on legume grains in order to reduce the economic losses. A laboratory experiment was conducted in August-November, 2019. The experiment was laid out at (30±2 ºC and 65±5% relative humidity), to investigate the insecticidal efficacy of Azadirachta indica (A. Juss) (neem) and Ricinus cummunis (L.) (castor) seeds oil that effect the various biological parameters of C. maculatus fed on Vigna radiata (mung beans) including mortality, oviposition, and adult emergence using three replication for each treatment. Four concentrations viz; (0.25, 0.50, 0.75 and 1%) each of the oil were prepared to observe the contact toxicity and surface protectant effect. Results showed that as percentage of concentrations increased mortality of adult beetles also increased with increased exposure time. In addition, among the dissimilar concentrations of oils, it was found that 0.50% of both oils were lethal concentrations (LC 50 ) which killed almost (50%) population of beetles after 48 hrs of exposure. Furthermore, both oils were effective by reducing (100%) oviposition, population emergence and seeds infestation rate as compared to control in which 75% infested grains were found including the large number of eggs and adults. These two oils provided best protection at their higher concentrations to mung beans against Callosobruchus maculatus. In conclusion, it is strongly recommended that oil extracts from seeds of neem and castor plants can be used to manage the stored grain pest up to the tolerable limits in integrated pest management. Moreover, the present study suggests further work on the efficacy of some other local plant extractions as an alternative to chemical pesticides.