Spore Density and Viability of Entomopathogenic Fungal Isolates from Indonesia, and Their Virulence against Aphis gossypii Glover (Homoptera: Aphididae).

The focus of this study was on quantifying fitness attributes, such as spore density and viability, and determining the virulence level against aphid (Aphis gossypii) nymphs of isolates from the fungal species Beauveria bassiana and Metarhizium anisopliae. The fungal isolates were obtained from several insects, including Plutella xylostella, Hypothenemus hampei, Bronstispa longissima, A. gossypii, Tenebrio molitor, and Leptocorisa acuta, that were collected from Indonesian islands, such as Sumatera, Java, and Sulawesi. Third instar aphid nymphs were inoculated via topical application of 10(6) conidia ml(-1) of the entomopathogenic fungal isolates. All of the B. bassiana and M. anisopliae isolates could produce very dense spores. The M. anisopliae isolate MaAg, which was obtained from the aphid, had the highest spore density at 6.70 × 10(8) conidia ml(-1). Among the B. bassiana isolates, the highest conidial viability belonged to isolate CPJW8, which was obtained from Chrysodeixis chalcites, with a 39% average viability. Among the M. anisopliae isolates, the highest viabilities belonged to the isolates MaAg and MaLa, which were obtained from L. acuta, with a 33% and 32% average viabilities, respectively. All of the B. bassiana and M. anisopliae isolates were virulent against aphid nymphs, with mortality rates ranging from 64% to 94%. The three most virulent isolates were BBY715 (94%), MPx (92%), and MaTm (92%), and the least virulent isolate was MaLa (64%). BBY715, the most virulent isolate, had the shortest lethal time median (LT50) against aphid nymphs at 2.97 hours, and MaLa had the longest LT50 at 61.81 hours.