Cercospora Leaf Spot of Eggplant
The infection can occur at any growth stage and is visible on leaves, petioles and stems. Initial symptoms appear as small, round and slightly sunken spots on the upper side of the older, lower leaves. Over time, the spots grow larger, more irregular and surrounded by a yellow halo. Later on, the leaf spots are visible on both leaf surfaces. The older spots merge and take on different aspects, depending on their location on the leaf. They range from brown to steal-grey (on upper side) and light brown (lower side). If the infection is heavy, leaves become curly and can drop off. Even though the fungus does not infect the fruits directly, it can lead to reduced fruit growth because of the lower productivity of the plants.
Cercospora melongenae is a plant-pathogenic fungus. The fungal spores can survive in plant debris and the soil for a minimum of 1 year. They are then carried in different ways onto the lower, older leaves. Most commonly they are spread by wind and water (rain and irrigation), but they can can be dispersed by infected tools and persons. It then moves up the stem to the younger foliage. Moisture and high relative humidity are favorable for the infection and development of the disease. It is thus more common during the rainy season (wet weather, continuous plant wetness).
Biological agents can help to control the infection. Bio-fungicides based on the bacteria Bacillus subtilis strain QST 713 can be used as foliar spray applications to compete with Cercospora melongenae. Plant extracts from Azadirachta indica (neem oil) may be helpful to control the infection, too.
An integrated approach should always be considered to control the disease. If fungicides are needed, products containing chlorothalonil, mancozeb or octanoic acid in combination with copper salt can be used as foliar spray and soil applications.