BIOLOGICALLY BASED TECHNIQUES TO LIMIT THE DISPERSAL OF INVASIVE PESTS
Location: Insect Behavior and Biocontrol Research Unit
Title: Evaluation of Metarhizium anisopliae, Beauveria bassiana and Paecilomyces fumosoroseus as entomopathogens of the cactus moth, Cactoblastis cactorum (Lepidoptera:Pyralidae)
Submitted to: Subtropical Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 15, 2010
Publication Date: October 15, 2010
Citation: Legaspi, J.C., Kanga, L.H., Legaspi, Jr, B.C. 2010. Evaluation of Metarhizium anisopliae, Beauveria bassiana and Paecilomyces fumosoroseus as entomopathogens of the cactus moth, Cactoblastis cactorum (Lepidoptera:Pyralidae). Subtropical Plant Science. 62:27-33.
Interpretive Summary: The cactus moth is a relatively new insect pest of cactus in the United States. The moth was first reported in Florida in 1989, but has since spread to South Carolina, Louisiana and parts of Mexico. Because it spends most of its life inside the cactus plant, it is protected from many control agents. In the laboratory, scientists at the USDA, ARS Center for Medical, Agricultural and Veterinary Entomology in collaboration with colleagues from Florida A&M University and the State of Florida tested the use of fungi that kill the egg and early larval stages of the moth which are found outside the plant. We found that the fungi did not infect the eggs, probably because the egg surface served as protective covering. However, the young cactus moth larvae were killed. We conclude that these fungi show promise as control agents, when used in an integrated pest management program against the cactus moth.
The 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 1st instar larvae of cactus moth larvae. 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 pathogencity found for M. anisopliae suggests this fungus could provide new avenues for the biological control of the cactus moth, targeting mainly the 1st instar larvae, and may complement current control strategies.