Summer and autumn rains decrease the viability of the fungus on stubble. The fungus is poorly adapted to survive on stubble and in soil through wet winter and spring conditions. Spores need a moisture film on the plant surface for a minimum of four hours to germinate and penetrate the tissue. More infection will result from longer periods of wetness. After penetration, the fungus colonises the plant tissue and develops a lesion within a few days.
Warmer temperatures increase the rate of symptom development and spore production.
Sowing infected seed poses the greatest risk of loss from anthracnose. European reports indicate that as little as one infected seed in 10,000 can result in severe epidemics under conducive conditions. The spread of the disease will be greater in higher rainfall regions and with warmer temperatures. However, the climate throughout Western Australian lupin growing areas will enable the disease to develop if seed infection levels are high. Yield loss will be greatest where infection becomes severe prior to flowering because flower heads are very susceptible to infection and pod set is dramatically reduced.