Trans-Stage effects of jatropha (Jatropha curcas) and castor (Ricinus communis) oils on Spodoptera frugiperda in laboratory

Abstract

This study aimed to evaluate the effects of jatropha and castor oil application on S. frugiperda eggs, specifically examining their influence on egg hatching, subsequent larval mortality, and pupae emergence. Thus, two bioassays were conducted in the laboratory; one for trans-stage effect by treating fall armyworm eggs with the oils and the second for direct application effect of the oils on fall armyworms 2^nd instar larvae. Four treatments were used for each assay in a complete randomized block: T1: Water; T2: Water+Omo; T3: Jatropha oil (1.25% v/v), and T4: Castor oil (1.25% v/v). For the trans-stage effect bioassay, batches of 10 eggs were sprayed with 1 mL of the treatment using a micropipette and maintained to the pupal stage, to evaluate egg hatching, larval mortality, and pupation rate. About the direct effect bioassay, batches of 10 individuals were sprayed with 2.5 mL of each treatment, and the larval mortality was recorded. The results showed that castor and jatropha oils had a trans-stage effect, resulting in larval mortality (df=3, p = 0.00441<0.05) and reduced pupation rate (df=3, p=0.00441<0.01). Also, larval mortality in the trans-stage assay was higher than that obtained by direct application of biopesticides on the larvae. This study suggests that an application of the jatropha or ricin oil from the egg stage could help to maximize their larvicidal efficacy.