Efficacy of Metarhizium anisopliae against the Greater Pumpkin Fly Dacus bivitattus

Abstract

The greater pumpkin flyDacus bivittatus(Bigot) is a fruit fly indigenous to Africa, whichcauses extensive damage to Cucurbitaceae. To control this pest, farmers rely on synthetic chemi-cals, often organophosphates, which have negative effects on human health and the environment.However, the sustainable management ofD. bivittatusmay be obtained through integrated pestmanagement (IPM) practices, with the use of biopesticides as a key component. In this study, theeffect of nine isolates of the entomopathogenic fungusMetarhizium anisopliae(Metschnikoff) Sorokin(ICIPE 18, ICIPE 20, ICIPE 30, ICIPE 48, ICIPE 62, ICIPE 69, ICIPE 84, ICIPE 91 and ICIPE 94) wasdirectly evaluated on adultD. bivittatusmortality. Adult flies were allowed to walk for 5 min on0.3 g of dry conidia of each isolate and monitored daily for 10 days. We also evaluated the effect ofsand inoculated withM. anisopliaeon larval and pupal mortality and adult eclosion and mortalityin three replicated experiments. Larvae were exposed to the same isolates at a concentration of1×107conidia/mLin sterile sand, and adult eclosion and mortality were monitored for 15 days.The median lethal time (LT50) of adults after direct exposure was shortest for ICIPE 18, ICIPE 20,ICIPE 30 and ICIPE 69 (3.11–3.52 days). In infested sand, larval mortality was highest for ICIPE 18and ICIPE 20 (≥42.50%), while pupal mortality was highest for ICIPE 30 (≥41.25%). The lowesteclosion was observed for ICIPE 18, ICIPE 20, ICIPE 30 and ICIPE 69 (≤40.00%). The LT50of adultseclosed from infested sand was shortest for ICIPE 18, ICIPE 20 and ICIPE 30 (4.48–6.95 days). ICIPE18, ICIPE 20, ICIPE 30 and ICIPE 69 are, therefore, potential isolates for subsequent field testing onD. bivittatuspopulations