PATHOGENS AND PARASITIC NEMATODES ASSOCIATED WITH POPULATIONS OF FALL ARMYWORM (LEPIDOPTERA: NOCTUIDAE) LARVAE IN MEXICO

Abstract

Larvae of fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith) and soil samples were collected in six Mexican states. Larvae were collected from whorl-stage corn, grain sorghum, forage sorghum, and Sudan grass fields in 64 locations during the summer of 2000, to determine the occurrence of entomopathogens and parasitic nematodes. A total of 5591 FAW larvae from 64 locations were examined for indigenous FAW biological control agents. Overall total larval mortality was 3.935%. The larval mortality percent due to entomopathogens and parasitic nematodes was 3.524%, other causes reached 0.411% of total mortality. Three species of entomopathogenic fungi representing two classes, Hyphomycetes (Nomuraea rileyi, and Hirsutella sp.) and Zygomycetes (Entomophthora sp.) were recovered from FAW larvae, and two species of Hyphomycetes (Metarhizium anisopliae and Beauveria bassiana) were isolated from soil samples. An unidentified microsporidian was recovered from four locations in the State of Jalisco, three from Michoacán, three from Nayarit, and one from Veracruz and Colima, respectively. Mermithid nematodes were recovered from 24 FAW larvae at three locations in Nayarit and three larvae were recovered from two locations in Veracruz. Six larvae showing symptoms of viral disease were collected from Sinaloa (2), Jalisco (2), Michoacán (1), and Nayarit (1). Entomopathogenic nematodes from the genus Heterorhabditis sp. and Steinernema sp. were isolated from soil samples from Colima in one and two locations, respectively. Steinernema sp., and Heterorhabditis sp. were isolated from soil in one location in Michoacán. Steinernema sp. was recovered from two locations of Jalisco. In this survey, N. rileyi, mermithid nematodes, and microsporidia were the most frequent pathogens and parasites.

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