Bean IPM

Legume ipmPIPE Diagnostic Series

Halo Blight

Pseudomonas syringae pv. phaseolicola


Figure 1 – Medium, circular, chlorotic to yellow-green (4 – 8 mm or ¼ – ½ inch diameter), necrotic (1 – 2 mm or 1/16 – 1/8 inch diameter), water-soaked lesions on upper and lower leaf surfaces; lesions may develop on petioles and stems

Figure 2 – Lesion coalescence, plant yellowing and translocation of toxin to new upper growth with leaf distortion; chlorosis may be less noticeable at high temperatures or later in the season

Figure 3 – Small to medium (less than 3 mm or 1/8 inch diameter), circular, water-soaked and necrotic lesions on bean pods and seed

Factors favoring
  • Infected seed, infested debris and volunteers from previous seasons
  • Rainstorms and sprinkler irrigation
  • Moderate temperatures with daily highs less than 25oC [77oF]
Lesions on leaves
Figure 1
Lesions coalesce on leaves
Figure 2
Lesions on seed and pod
Figure 3

H. F. Schwartz, Colorado State University, M. A. C. Langham, South Dakota State University, R. M. Harveson, University of Nebraska, and G. D. Franc, University of Wyoming

Photo credits

Courtesy of H. F. Schwartz [06/09]