Comparative Evaluation of Botanical Oils against Callosobruchus chinensis L. in Stored Black Gram

The pulse beetle Callosobruchus chinensis (L.) is a major storage pest of black wgram (Vigna mungo L.), causing severe seed loss and reduced germination. While botanical oils have shown insecticidal potential, most studies focus only on adult mortality, overlooking reproductive suppression.

Seven commercially available oils (neem, eucalyptus, peppermint, castor, mustard, sesame and sunflower) were applied at 5/ mL/kg seed under laboratory conditions. Adult mortality and oviposition (eggs per 100/ g seeds) were recorded monthly for four months. Correlation analysis examined the relationship between mortality and oviposition suppression.

Peppermint and eucalyptus oils consistently caused the highest mortality (93.33-80.00%) and reduced oviposition by 80.71% and 76.65%, respectively. Neem oil was also effective, whereas sesame and sunflower oils showed lower efficacy. A strong negative correlation (r = -0.99, p<0.001) indicated that treatments lethal to adults simultaneously suppressed reproduction. Peppermint, eucalyptus and neem oils offer long-lasting, dual-action protection against C. chinensis in stored black gram, combining adult mortality with oviposition deterrence. Using standardized commercial oils ensures reproducibility and provides a sustainable alternative to synthetic fumigants.