Submitted to: Journal of Nematology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/11/2005
Publication Date: 3/1/2006
Citation: Nguyen, K.B., Shapiro Ilan, D.I., Fuxa, J.R., Wood, B.W., Bertolotti, M.A., Adams, B.J. 2006. Taxonomic and biological characterization of Steinernema rarum found in the Southeastern United States. Journal of Nematology. 38:28-40. Interpretive Summary: Insect-killing nematodes are small round worms that kill insect pests but don't harm people or the environment. One way to expand the use of these nematodes is to find new species and strains. During soil surveys in Louisiana and Mississippi, we found two new strains of a nematode called Steinernema rarum. Previously this nematode had never been reported in the United States; it was only found in Argentina. In this study we described the genetic and morphological structure of the new nematode strain and compared it to similar nematodes. Relative to other nematodes, we also compared the ability of the new strain to kill a variety of insect pests such as fire ants, termites, citrus weevils, black cutworm, and fall armyworm. We found that the new nematode strain generally compares favorably with other nematodes and should be looked at further as a potential natural insecticide.
Technical Abstract: Two isolates of Steinernema sp. found in Louisiana and Mississippi, USA were identified as isolates of S. rarum. DNA sequences of ITS regions of the USA isolates are identical with sequences of Argentinean S. rarum strains Samiento and Noetinger, and have a two base pair difference from the Arroyo Cabral isolate from Cordoba, Argentina. SEM observations revealed several new structures in the USA isolates: female face views have a hexagonal-star perioral disc and eye-shaped lips; some females do not have cephalic papillae; lateral fields of infective juveniles are variable; there are two openings observed close to posterior edge of the cloaca. Virulence of the USA isolates to Anthonomus grandis, Diaprepes abbreviatus , Solenopsis invicta, and Coptotermes formosanus, Agrotis ipsilon, Spodoptera frugiperda, and Trichoplusia ni, and reproductive potential, was evaluated in comparison with other heterorhabditid or steinernematid nematodes. Results indicate the biocontrol potential of S. rarum (USA strains) merits further study.