Experimental pathogenicity of Erwinia aphidicola to pea aphid, Acyrthosiphon pisum

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Pea aphids were reared aseptically in the laboratory and fed on strains of Erwinia aphidicola, Erwinia herbicola, Klebsiella pneumoniae, Escherichia coli and bacterium W, an aphid enterobacterium, by mixing with a synthetic diet to determine whether these bacteria have pathogenicity to the insect. It turned out that Er. Aphidicola and Er. Herbicola grew in aphid gut, while K. pneumoniae, Es. Coli and bacterium W were effectively eliminated. In the case of Er. aphidicola, ingestion of a single dose of 10³CFU/ml was enough to infect aphid gut and to prevent post-final ecdysis growth of the insect. As a result, the body weight of the infected aphids was significantly reduced (p<0.01). A concentration of 10⁵CFU/ml of Er. aphidicola caused aphid mortality. In contrast, Er. herbicola demanded 10⁵CFU/ml to colonize in aphid gut, and seemed to have no effect on insect health.