Beauveria bassiana biocontrol with neem oil adjuvant is effective for the management of the cassava mosaic virus vector Bemisia tabaci in field trials

Cassava mosaic disease causes major losses of cassava crops in Southeast Asia. The disease is caused by the cassava mosaic virus, which is primarily transmitted by the tobacco whitefly (Bemisia tabaci). Chemical insecticides are widely used to control whitefly populations. However, their effectiveness is limited by environmental issues and whitefly resistance. Biocontrol agents such as entomopathogenic fungi are alternatives to chemical insecticides. We conducted two cassava field trials of the entomopathogenic fungus Beauveria bassiana for the control of whitefly populations. Comparison between plants treated with B. bassiana, buprofezin, or a combination of B. bassiana-buprofezin or B. bassiana-neem oil adjuvant, were tested in the same field. The whitefly adult populations were lowest in the B. bassiana/neem oil treatment group, with up to 86% reduction compared with the control six months after application. Natural enemies of insect pests were unaffected in the B. bassiana/neem oil and B. bassiana-only treatments. Our study revealed that integrated pest management using B. bassiana and neem oil was effective for controlling whiteflies and maintaining the natural balance of insects in cassava fields.