Biological Process Development Facility


Date of this Version


Document Type



PLANT DISEASE REPORTER, Vol. 62, No. 3 (March 1978), pp. 213-216.


Published by USDA-ARS


A leaf spot of field corn was shown to be caused by the bacterium Pseudomonas andropogonis. Leaf spot symptoms were observed over 3 years in several States. Inoculation of corn by vacuum infiltration of the bacteria was necessary to reproduce field symptoms.

A bacterial leaf spot disease of different cultivars of field corn was observed in early summer of 1973, 1974, and 1975. Leaves with essentially the same symptoms were obtained from South Dakota, Iowa, Kansas, Nebraska, and Michigan. The same symptoms were also seen in Wisconsin. Symptoms consisted of circular to ellipsoidal, tan to brown spots, with irregular margins. The spots were 1 to 4 mm in diameter, with one or more darker brown rings within the lesions. Some spots were surrounded by a chlorotic ring 1 mm wide. All spots tended to have a slightly sunken appearance. Occasionally the spots coalesced into irregular, somewhat elongated blotches. Water-soaking of young lesions was also seen. Bacteria were routinely isolated from the lesions. Because the symptoms did not correspond with previous reports of bacterial diseases of corn, experiments were undertaken to determine the causal bacterium and compare it with known bacterial pathogens of corn. The pathogen was subsequently identified as Pseudomonas andropogonis, previously reported to cause bacterial stripe disease of sorghum, sudangrass, teosinte, johnsongrass, field corn, broomcorn, and sweet corn. As P. stizolobii (syn. P. andropogonis), the bacterium causes leaf spot diseases of Bougainvillea, clover, and other leguminous plants.