|Shapiro Ilan, David|
Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/12/2004
Publication Date: 1/1/2005
Citation: Shapiro Ilan, D.I., Stuart, R.J., Mccoy, C.W. 2005. Characterization of biological control traits in the entomopahogenic nematode Heterorhabditis mexicana (MX4). Biological Control. 32:97-103. Interpretive Summary: Insect-killing nematodes are small round worms that kill insect pests but don't harm people or the environment. Discovery of new insect-killing nematode species can expand the use of these beneficial organisms as natural pest control agents. Once a new species is discovered, the pest control abilities of the new nematode should be characterized. In this study we characterized the pest control abilities of a newly discovered nematode species called Heterorhabditis mexicana. Our results indicate that this new nematode is naturally attracted to insects. We compared the new nematode to several other beneficial nematode species and found the new species to possess only mediocre pest control abilities. In the course of the study, however, another nematode species (Steinernema riobrave) was found to be superior in its ability to withstand extremes in heat and exposure to low oxygen levels. The superiority of Steinernema riobrave in these traits could offer advantages for incorporating this species into pest management programs.
Technical Abstract: Our objective was to estimate the biocontrol potential of the recently discovered entomopathogenic nematode species, Heterorhabditis mexicana (MX4 strain). In laboratory experiments, we compared H. mexicana to several other entomopathogenic nematodes for virulence to several insect pests, environmental tolerance (to heat, desiccation and low oxygen levels), and host seeking ability. Heterorhabditis mexicana expressed low or intermediate capabilities in all traits except in host seeking ability and virulence to the lesser mealworm, Tenebrio molitor, for which no differences among nematodes were detected. Heat tolerance was more than five fold greater in Steinernema riobrave than H. mexicana, H. indica, and H. bacteriophora. Mortality of nematodes following exposure to low oxygen levels was lowest in S. riobrave followed by glaseri and higher in the other species (H. mexicana, H. bacteriophora, and H. indica). The apparent superiority of S. riobrave in heat and low oxygen tolerance is likely to be advantageous in biocontrol programs. We conclude that H. mexicana exhibits a cruiser type of search strategy and, relative to other entomopathgenic nematodes, generally possesses moderate abilities in biocontrol traits.