Indigenous Metarhizium rileyi as Virulent Entomopathogenic Fungus for the Invasive Armyworm Species
2023.09.19
Melissa P. Montecalvo, Marcela M. Navasero, Mario V. Navasero,
Janren Sarah T. Macaraig, and Jose Mari M. Navasero
Migratory insect pests such as fall armyworm (Spodoptera frugiperda J.E. Smith) and onion armyworm (S. exigua Hübner) are threats to corn and rice production in the Philippines, respectively. Infestation results in severe outbreak and economic loss. One of the promising eco-friendly solutions against these insect pests are biological control agents. Beneficial microorganisms known as entomopathogens are effective microbials which kill and cause abnormalities to the target insect pests. In a study conducted by the National Crop Protection Center of the College of Agriculture and Food Science, University of the Philippines Los Baños; the entomopathogenic fungus, Metarhizium rileyi (Farl.) Kepler, SA Rehner & Humber, was successfully isolated from these invasive armyworm species.
The bioefficacy of M. rileyi was tested against various stages of armyworm including eggs, various larval instars, prepupa, and pupa in laboratory bioassays. The M. rileyi from onion armyworm was pathogenic to three armyworm species such as onion, fall, and paddy (Mythimna separata (Walker)) armyworms. In general, the fungus did not affect the hatchability of eggs, but later caused mortality to the neonates from hatched treated eggs. The fungus was more infective against young larvae of the armyworm species. Higher conidial concentrations were required for lethal infection in paddy armyworm due to larger larval body as compared with other armyworm species. At present, M. rileyi from fall armyworm has been assessed against this insect host. Mummification of the larval cadavers, exhibited as white fungal growth that later changed to green during sporulation, confirmed fungal infection due to M. rileyi. Prepupae and pupae were not significantly affected but slight abnormalities were observed in adults. Our findings revealed the virulence of native M. rileyi against armyworms suggesting its potential as biological control agent against these major economic insect pests of onion and corn. Hence, initiatives on formulation of M. rileyi as powder and emulsifiable concentrate are underway. So far, its efficacy against fall armyworm in corn production was observed in field trials.
REFERENCES
Montecalvo, M. and Navasero, M. (2023). Susceptibility of Pre-adult Biological Stages of Mythimna separata (Walker) (Lepidoptera: Noctuidae) to Three Entomopathogenic Fungi (Hypocreales). The Philippine Agricultural Scientist 106(1):7-14.
Montecalvo, M. P., Macaraig, J. S. T., Navasero, M. M. and Navasero, M. V. (2022). Biocontrol efficacy of native Metarhizium rileyi to various life stages of Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae). Journal of the International Society for Southeast Asian Agricultural Sciences 28(1):1-11.
Montecalvo, M. P., Navasero, M. M. and Navasero, M. V. (2022). Lethal effect of native Metarhizium rileyi (Farlow) Samson isolate to invasive fall armyworm, Spodoptera frugiperda (J.E. Smith), infesting corn in the Philippines. International Journal of Agricultural Technology 18:257-270.
Montecalvo, M. P. and Navasero, M. M. (2021). Metarhizium (=Nomuraea) rileyi (Farlow) Samson from Spodoptera exigua (Hübner) cross infects fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) larvae. Philippine Journal of Science 150:193-199.
Montecalvo, M. P. and Navasero, M. M. (2020). Effect of entomopathogenic fungus Metarhizium (Nomuraea) rileyi (Farl.) Samson on the third instar larvae of the onion armyworm, Spodoptera exigua Hübner (Lepidoptera: Noctuidae) under laboratory conditions. The Philippine Agricultural Scientist 103:140-145.
Melissa P. Montecalvo, Marcela M. Navasero, Mario V. Navasero,
Janren Sarah T. Macaraig, and Jose Mari M. Navasero
Migratory insect pests such as fall armyworm (Spodoptera frugiperda J.E. Smith) and onion armyworm (S. exigua Hübner) are threats to corn and rice production in the Philippines, respectively. Infestation results in severe outbreak and economic loss. One of the promising eco-friendly solutions against these insect pests are biological control agents. Beneficial microorganisms known as entomopathogens are effective microbials which kill and cause abnormalities to the target insect pests. In a study conducted by the National Crop Protection Center of the College of Agriculture and Food Science, University of the Philippines Los Baños; the entomopathogenic fungus, Metarhizium rileyi (Farl.) Kepler, SA Rehner & Humber, was successfully isolated from these invasive armyworm species.
The bioefficacy of M. rileyi was tested against various stages of armyworm including eggs, various larval instars, prepupa, and pupa in laboratory bioassays. The M. rileyi from onion armyworm was pathogenic to three armyworm species such as onion, fall, and paddy (Mythimna separata (Walker)) armyworms. In general, the fungus did not affect the hatchability of eggs, but later caused mortality to the neonates from hatched treated eggs. The fungus was more infective against young larvae of the armyworm species. Higher conidial concentrations were required for lethal infection in paddy armyworm due to larger larval body as compared with other armyworm species. At present, M. rileyi from fall armyworm has been assessed against this insect host. Mummification of the larval cadavers, exhibited as white fungal growth that later changed to green during sporulation, confirmed fungal infection due to M. rileyi. Prepupae and pupae were not significantly affected but slight abnormalities were observed in adults. Our findings revealed the virulence of native M. rileyi against armyworms suggesting its potential as biological control agent against these major economic insect pests of onion and corn. Hence, initiatives on formulation of M. rileyi as powder and emulsifiable concentrate are underway. So far, its efficacy against fall armyworm in corn production was observed in field trials.
REFERENCES
Montecalvo, M. and Navasero, M. (2023). Susceptibility of Pre-adult Biological Stages of Mythimna separata (Walker) (Lepidoptera: Noctuidae) to Three Entomopathogenic Fungi (Hypocreales). The Philippine Agricultural Scientist 106(1):7-14.
Montecalvo, M. P., Macaraig, J. S. T., Navasero, M. M. and Navasero, M. V. (2022). Biocontrol efficacy of native Metarhizium rileyi to various life stages of Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae). Journal of the International Society for Southeast Asian Agricultural Sciences 28(1):1-11.
Montecalvo, M. P., Navasero, M. M. and Navasero, M. V. (2022). Lethal effect of native Metarhizium rileyi (Farlow) Samson isolate to invasive fall armyworm, Spodoptera frugiperda (J.E. Smith), infesting corn in the Philippines. International Journal of Agricultural Technology 18:257-270.
Montecalvo, M. P. and Navasero, M. M. (2021). Metarhizium (=Nomuraea) rileyi (Farlow) Samson from Spodoptera exigua (Hübner) cross infects fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) larvae. Philippine Journal of Science 150:193-199.
Montecalvo, M. P. and Navasero, M. M. (2020). Effect of entomopathogenic fungus Metarhizium (Nomuraea) rileyi (Farl.) Samson on the third instar larvae of the onion armyworm, Spodoptera exigua Hübner (Lepidoptera: Noctuidae) under laboratory conditions. The Philippine Agricultural Scientist 103:140-145.