Location: Screwworm ResearchTitle: Occurrence of entomopathogenic fungi and parasitic nematodes on Spodoptera frugiperda (Lepidoptera: Noctuidae) larvae collected in Central Chiapas, Mexico) Author
Submitted to: Florida Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/8/2013
Publication Date: 6/1/2013
Citation: Ruiz-Najera, R.E., Ruiz-Estudillo, R.A., Sanchez-Yanez, J.M., Molina-Ochoa, J., Skoda, S.R., Coutino-Ruiz, R., Pinto-Ruiz, R., Guevara-Hernandez, F., Foster, J.E. 2013. Occurrence of entomopathogenic fungi and parasitic nematodes on Spodoptera frugiperda (Lepidoptera: Noctuidae) larvae collected in Central Chiapas, Mexico. Florida Entomologist. 96(2):498-503. Interpretive Summary: The fall armyworm (FAW) is an economically important pest of corn and other crops. Control for this pest has mostly relied on application of insecticides. In this survey, we determined natural control agents affecting FAW collected from early season corn fields in southern Mexico. From 1247 larvae examined, overall larval mortality was 16.36%. Larval mortality due to entomopathogens and parasitic nematodes was 12.99%; nematodes, entomopathogenic fungi, and microsporidia were the prevalent natural control agents and they affected later stages of the larvae. Larval mortality by unknown causes was about 3.37%. Further surveys to determine the seasonal and environmental conditions that favor these natural control agents will aid in the ability to use biological control for FAW and reduce the use of insecticides.
Technical Abstract: Fall armyworm larvae (FAW), Spodoptera frugiperda (J. E. Smith) were collected from whorl-stage cornfields, between the V2 and V4 stages, in 22 localities of Central, Chiapas, México, called "La Frailesca" during late June 2009 to determine the occurrence of native entomopathogens and parasitic nematodes and to determine the most parasitized instars. A total of 1247 larvae were examined in search of native biological control agents. Overall larval mortality was 16.36%. The larval mortality due to entomopathogens and parasitic nematodes was 12.99%, mermithid nematodes of the species Hexamermis probably albicans Siebold were isolated from 105 FAW larvae (8.42%) with highest incidence from the 4th, 5th, 6th and 3rd instars, respectively. A Hyphomycete, Nomuraea rileyi Farlow (Samson) was recovered from 38 larvae (about 3.05% parasitim) with highest incidence from the 5th, 3rd, 4th, and 6th instars, respectively. Lowest percentage of FAW larval parasitism was caused by unidentified microsporidian or microsporidium (1.52%), infecting 19 larvae in the 6th, 5th and 3rd instars, respectively. First and 2nd instars did not show parasitism. This information is useful in designing future biological control programs.