Evaluation of Metarhizium anisopliae, Beauveria bassiana and Paecilomyces fumosoroseus as Entomopathogens of the Cactus Moth, Cactoblastis cactorum (Lepidoptera:Pyralidae)

The three fungal pathogens Metarhizium anisopliae (Metchnikoff) Sorokin (Hypocreales: Clavicipitaceae), Paecilomyces fumosoroseus (Wize) Brown & Smith (Deuteromycotina: Hyphomycetes), and Beauveria bassiana (Bals.-Criv.) Vuill. (Hypocreales: Clavicipitaceae) were evaluated as potential biological control agents against the cactus moth, Cactoblastis cactorum (Berg) (Lepidoptera: Pyralidae). The entomopathogens, M. anisopliae and P. fumosoroseus, tested against the cactus moth eggs did not infect the eggs. The chorion may serve as protective covering for the eggs that prevents infection. However, C. cactorum was found to be a suitable host for both M. anisopliae and B. bassiana. Mean (± SE) conidial germination was 95.6 ± 0.5% for M. anisopliae and 91.6 ± 0.7% for B. bassiana. The fungus M. anisopliae was highly pathogenic to 1 instar larvae of cactus moth. The relative virulence at LC50 of M. anisopliae as compared to B. bassiana was over 1,000-fold greater at 7-, 14-, and 21-d post -treatments. A total of 289 dead cactus moths collected from the treatment groups were investigated for fungal infection, and 98% of them showed mycosis at the end of 21 d of the experiments. Cadavers from the controls showed no fungal growth at the end of the experimental period. The greater pathogenicity found for M. anisopliae suggests this fungus could provide new avenues for the biological control of the cactus moth, targeting mainly the 1 instar larvae, and may complement current control strategies. Additional