EFFICACY OF BEAUVERIA BASSIANA (STRAIN ACCC30108) IN CONTROL OF THE PLANTAIN-BANANA WEEVIL, COSMOPOLITES SORDIDUS GERMAR IN VITRO

Abstract

The plantain banana weevil, Cosmopolites sordidus is one of the major constraints to the production of Musa spp globally, resulting in severe damages or even total crop failures. Laboratory testing with 4 different concentrations of the entomophagous fungus Beauveria bassiana (strain ACCC30108) revealed that fungal concentration as well as time (days after treatment, DAT) had significant impacts on adult weevil mortalities (P<0.05). Two high treatment concentrations used in this study (i.e.3mg/ml or 3x10⁷ spores/ml and 2mg/ml or 2x10⁷ spores/ml respectively) yielded similar results of between 4-92% mortalities of the weevil, but with LT₅₀ of 26DAT and 28DAT respectively. The lower concentration (1mg/ml or 1x10⁷ spores/ml and the control i.e. 0mg/ml or distilled water) on the other hand, respectively yielded 4-68%, with LT₅₀ 36DAT; and a paltry 4% mortality by end of trials i.e. 40DAT; suggesting that lower concentrations were insufficient to cause substantial weevil mortalities. Cadavers of dead weevils showed some white mycelial mass, visible only at intersegmental areas initially, but later covering the entire body, indicative of fungal (B. bassiana) cause of death. The study has confirmed B. bassiana as a possible biological control agent for management of this key pest. Follow-up tests in the field would ultimately reveal/confirm its true potential in this quest for a suitable, effective and environmentally-friendly biocontrol agent for sustainable management of this key pest.