Bean IPM

Legume ipmPIPE Diagnostic Series

Common Bacterial Blight

Xanthomonas axonopodis pv. phaseoli


Figure 1 – Large (often greater than 12 mm or ½ inch diameter), irregular, brown, necrotic, watersoaked lesions that may be bordered by a narrow yellow border on upper and lower leaf surfaces; lesions often develop from leaf margins and also may develop on petioles and stems.

Figure 2 – Younger lesions may be circular, flaccid, with small water-soaked areas apparent on lowersurface at the edge and interveinal area of an infected leaf.

Figure 3 – Small to medium (less than 3 mm or 1⁄8 inch diameter), circular to irregular, water-soaked, red-brown lesions on bean pods.

Factors favoring
  • Infected seed, infested debris and volunteers from previous seasons
  • Rainstorms and sprinkler irrigation
  • Warm temperatures with daily highs greater than 30°C [86°F]
Leaf with lesions
Figure 1
Leaf with lesions
Figure 2
Pod with lesions
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

H.F. Schwartz, Colorado State University