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Title: Enteric bacteria of field-collected Colorado potato beetle larvae inhibit growth of the entomopathogens Photorhabdus temperata and Beauveria bassiana

Author
item Blackburn, Michael - Mike
item Gundersen-Rindal, Dawn
item Weber, Donald
item Martin, Phyllis
item Farrar, Robert

Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/19/2007
Publication Date: 9/1/2008
Citation: Blackburn, M.B., Gundersen, D.E., Weber, D.C., Martin, P.A., Farrar, R.R. 2008. Enteric bacteria of field-collected Colorado potato beetle larvae inhibit growth of the entomopathogens Photorhabdus temperata and Beauveria bassiana. Biological Control. 46(3)434-441.

Interpretive Summary: Some nematodes (tiny worms) can attack and kill pest insects by infecting them with disease causing bacteria. The bacteria kill the insects and digest them, while the nematodes feed on the bacteria and produce more nematodes that can infect more insects. Although these nematodes can kill Colorado potato beetle, they cannot reproduce within them, limiting their usefulness for controlling this important pest insect. We have discovered that several types of bacteria that live in the gut of the beetle can escape the gut after the beetle dies, inhibit the growth of the nematode's pest-killing bacteria, and prevent the nematode from reproducing. Many of these bacteria also inhibit the growth of a fungus that kills pest insects. These results will be valuable to those attempting to control Colorado potato beetle with nematodes, and useful to scientists searching for other nematode-bacteria combinations to control this damaging pest.

Technical Abstract: In a prior study we provided evidence that the failure of the nematode Heterorhabditis marelatus Liu and Berry to reproduce in the Colorado potato beetle, Leptinotarsa decemlineata (Say), was due to interference from the enteric bacteria of the beetle. Specifically, the enteric bacteria inhibited the growth of Photorhabdus temperata Fischer-Le Saux, the enteric symbiont of the nematode, in vitro. However, this study was based on a laboratory culture of L. decemlineata, and we wished to determine if similar bacteria were present in the field. Therefore we cultured the enteric bacteria of 4th instar larvae collected from the field at two locations in Maryland and Virginia. Representatives of the genera Pantoea, Enterobacter, Pseudomonas, Acinetobacter, Serratia, Stenotrophomonas, Curtobacterium, Bacillus, Lactococcus and Enterococcus were identified by sequencing of their 16S rDNA. Isolates belonging to the genera Pantoea, Enterobacter, Pseudomonas, Serratia and Bacillus inhibited the growth of Photorhabdus temperata. A number of these isolates also inhibited the entomopathogenic fungus Beauveria bassiana (Balsamo) Vuillemin in vitro.