Influence of Moisture and Inoculum Concentration on Infection of Philodendron selloum by Erwinia chrysanthemi. R. A. Haygood, Graduate Research Assistant, Department of Plant Pathology, North Carolina State University, Raleigh 27650. D. L. Strider, Professor, Department of Plant Pathology, North Carolina State University, Raleigh 27650. Plant Dis. 65:727-728. Accepted for publication 8 December 1980. Copyright 1981 American Phytopathological Society. DOI: 10.1094/PD-65-727.

Free moisture maintained on wounded or unwounded Philodendron selloum leaves 72 hr before inoculation with Erwinia chrysanthemi at 2 × 10⁸ colony-forming units per milliliter had no effect on disease severity 5 days after inoculation. Differences in disease severity were significant between unwounded leaves misted for 0 and 24 hr after similar inoculation and between wounded leaves misted for 0, 6, and 24 hr after inoculation. At the inoculum concentration of 2 × 10⁸ colony-forming units per milliliter, misting for longer than 24 hr after inoculation did not affect disease severity. Differences in disease severity were significant among wounded leaves inoculated with 2 × 10⁸, 2 × 10⁶, and 2 × 10⁴ colony-forming units per milliliter. Differences on unwounded leaves were significant only between leaves inoculated with 2 × 10⁸ colony-forming units per milliliter and those inoculated with the two lower concentrations. Longer misting times after inoculation were required before significant differences were detected on the wounded and unwounded leaves inoculated with the lower concentrations.

Keyword(s): bacterial blight, foliar plants.