Initially, brown irregular spots appear on the lower side of the leaves. The older leaves, which are closer to the ground are mostly affected by the disease. The leaves become dry and brown as the disease progresses and might also curl and eventually drop. Under severe infestation, the plant might defoliate completely. Initially, the disease symptoms are obvious on the lower surface of the leaves as indistinct spots in the form of olivaceous specks. Later on, light brown to grey mouldy growth of the fungus covers the entire lower surface. In severe cases, necrotic spots can also be seen on the upper surface of the leaves. Infected leaves ultimately dry and defoliate. The disease progresses upwards from lower leaves and infects stem and fruits and produces similar symptoms. Symptoms might be confused with P. abelmoschi, which causes sooty black angular spots.
The leaf spots are caused by the fungus Cercospora malayensis and Cercospora abelmoschi. It survives and overwinters on infected plant debris in the soil and thus infects roots and lower leaves of the okra plants. The spores are spread secondarily via wind, rain, irrigation and mechanical tools. Leaf spots are very common during humid season, as the fungi favour warm and wet weather. Rainfall and high humidity favour infection, disease development and sporulation of the pathogens on the leaves.
To this day, we are not aware of any biological control method available against this disease. If you know of any successful method to reduce the incidence or the gravity of the symptoms, please contact us.
Always consider an integrated approach with preventive measures and biological treatments, if available. Spray fungicide on the lower side of leaves in the afternoon. Use protective fungicides as Copper oxychloride @ 0.3%, mancozeb @ 0.25% or zineb @ 0.2% a month after sowing and repeat this procedure at fortnightly intervals, depending on severity.