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Infection of Onion Leaves by Pseudomonas cepacia. S. O. Kawamoto, Former Graduate Assistant, now Research Technician, Department of Plant Pathology, New York State College of Agriculture and Life Sciences, Cornell University, Ithaca, New York, 14850; J. W. Lorbeer, Professor, Department of Plant Pathology, New York State College of Agriculture and Life Sciences, Cornell University, Ithaca, New York, 14850. Phytopathology 64:1440-1445. Accepted for publication 4 June 1974. DOI: 10.1094/Phyto-64-1440.

In artificial inoculations of onion leaf parts, Pseudomonas cepacia infected only wounded onion tissue. Inoculations involving wounding tissues by means of a needle (stab inoculations) resulted in small lesions; spray inoculations without wounds were unsuccessful. Lesions expanded very slowly unless free moisture was added to the inoculation site. Water-soaking the lesion by hard sprays caused rapid lesion expansion. The tissue at the juncture of the leaf blade and sheath (the leaf blade axil) was especially susceptible when stab inoculated and wetted. Rate of lesion development increased with more frequent wetting of leaves and/or as temp was elevated to 32 C.