Disease Note.

Unusual Occurrences of Bacterial Leaf Blight on Maize and Sorghum in Central Illinois. D. G. White, Department of Plant Pathology, University of Illinois, Urbana 61801. J. K. Pataky, Department of Plant Pathology, University of Illinois, Urbana 61801; and R. E. Stall, Department of Plant Pathology, University of Florida, Gainesville 32611. Plant Dis. 78:640. Accepted for publication 24 March 1994. Copyright 1994 The American Phytopathological Society. DOI: 10.1094/PD-78-0640D.

Water-soaked linear lesions of leaves emerging from whorls, symptoms typical of bacterial leaf blight, caused by Acidovorax avenae subsp. avenae (syn. Pseudomonas avenae), were noted in three of the past four years on various types of maize (Zea mays L.) and sorghum (Sorghum bicolor (L.) Moench ) grown in Urbana, Illinois. Symptoms were severe following heavy rains in August 1990. In 1992, severe symptoms on white and bicolor sh2 sweet corn hybrids corresponded with about 35 cm of rain in July. When approximately 61 cm of rain fell from June through August 1993, symptoms were severe on sweet corn, field corn, broom corn (S. vulgare), and grain sorghum. Some sh2 sweet corn lines were extremely susceptible. Apparently, A. a. avenae was widespread when rainy weather provided conditions for infection. Pure cultures isolated from greenhouse-grown corn that had been inoculated with a mixture of bacterial strains obtained in 1993 from field-infected corn and sorghum leaves were identified as A. a. avenae from fatty acid profiles. Subsequently, strains from corn, broom corn, and grain sorghum caused symptoms on all three inoculated hosts. This disease is unlikely lo be prevalent or cause substantial damage in central Illinois when rainfall is more typical; however, severe outbreaks of bacterial leaf blight may occur sporadically in the southeastern United Slates where the pathogen overwinters on weed hosts (1,2), environmental conditions frequently are favorable for infection, and a few of the highly susceptible sh2 sweet corn hybrids are widely grown.