Examine leaves and flowers of 15 plants at each of 10 or more locations in the paddock. One fungicide application is adequate for most faba bean crops. If the disease is present, examine the crop again immediately upon first flowering. Fungicide application before flowering is unlikely to lead to a yield increase. The registered fungicides will only prevent new infection - they do not cure existing infections.
Infection takes place within a few hours of rain.
Spraying after rain will not control these infections. Fungicide protection lasts from two to three weeks after application. Apply the fungicide a few days prior to expected rain. If conditions are fine for three weeks after application, the spray will have no value. Growth which occurs after spraying and lower leaves in a dense canopy will not be protected.