Bean IPM

Legume ipmPIPE Diagnostic Series

Bacterial Brown Spot

Pseudomonas syringae pv. syringae


Figure 1 – Small (approximately 1 mm or 1⁄16 inch diameter), circular, brown, necrotic, water-soaked lesions on upper and lower leaf surfaces; lesionsmay develop on petioles and stems.

Figure 2 – Lesion coalescence and shot-hole effects on ragged leaves and canopy; watersoaking may be absent at this stage.

Figure 3 – Large (greater than 3 mm or 1⁄8 inch diameter), circular, water-soaked and necrotic lesions on bean pods.

Factors favoring
  • Infected seed, infested debris and volunteers from previous seasons
  • Susceptible weeds such as hairy vetch
  • Rainstorms and sprinkler irrigation
  • Moderate temperatures with daily highs less than 30°C [86°F]
Leaf with lesions
Figure 1
Leave with worsening lesions and holes
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

Courtesy of R.M. Harveson & H.F. Schwartz [06/09]