It is likely to have the greatest impact north of Perth in areas with more than 450 mm annual rainfall, as it prefers warm conditions and high humidity. To correctly diagnose the disease, check plants for small reddish-brown circular spots on leaves, flowers, and stems. Lesions on leaves enlarge and develop a grey, dead centre with reddish-brown rim or margin. Damage caused by red-legged earth mite can be mistaken for chocolate spot. It starts as silvery patches which become reddish-brown, similar in colour to chocolate spot but with large irregularly shaped areas without the grey centre.
Fungicides can reduce disease severity and increase yields.
The greatest impact of this disease is through abortion of infected flowers. The greatest yield increases are therefore achieved with sprays applied during flowering. Chocolate spot can develop very rapidly under suitable weather conditions. Inspect crops once a week until the weather starts to warm up in spring and then two or three times a week until the crop matures. Examine leaves and flowers of 15 plants at each of 10 or more locations in the paddock.