Efficacy of cassava leaf bio-fumigant against <i>Tribolium castaneum</i>, <i>Rhyzopertha dominica</i>, and their symbiotic bacteria in comparison to phosphine fumigation

Symbiotic bacteria in insects aid in detoxifying insecticides, contributing to resistance against synthetic pesticides. This study focuses on Tribolium castaneum and Rhyzopertha dominica, two major grain pests resistant to phosphine. A biofumigant that was developed from cassava leaves was tested against above two stored grain pests and with its proven pesticidal properties were further evaluated against endosymbiotic bacteria associated with these insects. The response of characterised compound of Cassava Leaf Bio-fumigant (CLBf) against in vitro culture of endosymbiotic bacteria was compared to phosphine. Mortality assays revealed that CLBf achieved 100% mortality for T. castaneum and R. dominica at concentrations of 49.84 ppm and 35.6 ppm, respectively, within a 5-minute exposure. The antibacterial effects of CLBf and phosphine were assessed by measuring the growth inhibition zones on Mueller Hinton agar plates. CLBf exhibited significant antibacterial activity against the endosymbionts of both insects, whereas the bacterial strains showed resistance to phosphine. The study highlights the role of endosymbiotic bacteria in pesticide detoxification.