Silver nanoparticles containing stearic acid isolated from Catharanthus roseus: Ovicidal and oviposition-deterrent activities on Earias vittella and ecotoxicological studies

Abstract

In the recent past, many agrochemicals have been used to control pests, but many of these fail due to the development of resistance. Many researchers, therefore, concentrate on developing new pesticide formulations from natural resources (plants/microorganism). In the present study, different extracts from Catharanthus roseus (Madagascar periwinkle) was evaluated for their ovicidal and oviposition deterrent activities against Earias vittella (spiny bollworm). Among the tested extracts DCM (Dichloromethane) extract showed highest ovicidal activity (70.47%) and oviposition deterrent activity (75.41%) against E. vittella. Based on this biological activity, DCM extract was fractionated and isolated 7 fractions; all of these were evaluated for their ovicidal and oviposition deterrent activity against E. vittella. Maximum ovicidal and oviposition deterrent activity was recorded in fraction 5, followed by the 7th fraction. Stearic acid was isolated from fraction 5 and was subjected to nanoparticle synthesis. This nanoparticle was tested for its effects against E. vittella. It was found to exhibit 100% oviposition deterrent and 95% ovicidal activities against E. vittella, and also reduced the protein (53.63%), glutothionine esterase (39.16%), and esterase activity (45.25%) of the treated larvae. The synthesized nanoparticle was subjected to ecotoxicology evaluation against Daphnia sp. (water fleas) and Cyprinus carpio (common carp). The nanoparticle showed >100 mg/L for EC50 and LC50 against both aquatic organisms. Based on the result, it could be studied further to develop the ecofriendly formulation with stability studies for agriculture pest management.