Bean IPM

Legume ipmPIPE Diagnostic Series

Yeast Spot

Nematospora & Eremothecium spp.


Symptoms appear after insects such as stink bugs (Megalotomus spp.) and lygus bugs (Lygus spp.) transmit the yeast organism to pods and developing seeds. Spores germinate and infect the seeds, producing irregular, slightly sunken rose, tan or brown lesions about 1 mm in diam.

Factors favoring
  • Presence of previously infested crop debris
  • Lack of crop rotation
  • Poor sanitation of previous legume and weed debris
  • Contaminated seed
  • Susceptible varieties
  • Moderate to high moisture conditions favor slugs
  • Infection at V2 – R2 results in plant death, and/or reduced pod set, poor seed fill, and yield loss
Yeast spot
Yeast spot
Additional Resources

H. F. Schwartz, Colorado State University and S. K. Mohan, University of Idaho

Photo credits

Gerald Holmes, Valent USA Corporation,