The Entomopathogenic Fungi Metarhizium anisopliae and Beauveria bassiana for Management of the Melon Fly Zeugodacus cucurbitae: Pathogenicity, Horizontal Transmission, and Compatability with Cuelure

SIMPLE SUMMARY: The melon fly Zeugodacus cucurbitae is an invasive fruit fly that causes extensive damage to many fruit crops. Sustainable management of this pest can be achieved through environmentally friendly and safely integrated pest management (IPM), in which the use of biopesticides is a key component. In this study, various isolates of entomopathogenic fungi were evaluated on two developmental stages of this pest. The fungal isolate ICIPE 69 has the greatest potential. The study also evaluated whether ICIPE 69 could be used together with the male pheromone of the melon fruit fly, as well as whether infected flies could contaminate clean flies. Our study indicates that ICIPE 69 can be included in IPM packages to reduce yield losses. ABSTRACT: In the laboratory, the pathogenicity of thirteen isolates of Metarhizium anisopliae (Metschnikoff) Sorokin and two isolates of Beauveria bassiana (Balsamo) Vuillemin against the melon fly Zeugodacus cucurbitae (Coquillett) were assessed by exposing adults to 0.3 g of dry conidia (~3 × 10(9) conidia) of each isolate for 5 min and monitoring mortality for up to 5 days. Compatibility with a male pheromone, cuelure, (4-(p-acetoxyphenyl)-2-butanone), was determined by testing conidial germination and germ tube growth of the most promising isolate, M. anisopliae ICIPE 69, in the presence of cuelure at different temperatures. For horizontal transmission, the flies were separated by sex, separately exposed to M. anisopliae ICIPE 69, and subsequently mixed with non-exposed flies from the other sex. The most pathogenic isolates were M. anisopliae ICIPE 69, 18, and 30, causing mortalities of 94, 87, and 81%, with 5 days post-exposure, respectively. Metarhizium anisopliae ICIPE 69 caused the highest pupal mortality of 74%, with 15 days post-exposure. Horizontal transmission of M. anisopliae ICIPE 69 among male and female Z. cucurbitae was confirmed by 59 and 67% mortality after exposure to infected donor males and females, respectively. Metarhizium anisopliae ICIPE 69 affected the oviposition, but not hatchability, of infected Z. cucurbitae females. Metarhizium anisopliae ICIPE 69 is, therefore, a potential isolate for biopesticide development for Z. cucurbitae management in cucurbit production systems.