This is the most important fungal disease of groundnut. Losses due to this disease may go up to 15-50% and 70%, if associated with rust (Puccinia arachidicola).
Symptoms :All the aerial parts of the plants are attacked. In case of attack by Cercosporidium personatum, the leaf spots are circular (1-6 mm dia.), slightly pale in the beginning, turning to dark brown to black necrotic areas. There is no halo around the young spots. While in case of Cercospora arachidicola, the leaf spots are circular to irregular in outline (1-10 mm in dia.) and tend to coalesce late, surrounded by yellow halo from the very beginning. The spots are reddish brown to black on upper surface, while on lower surface; these are light brown in colour. Cercosporidium personatum appears 30 days earlier than the other one and more dangerous as it produces many more spots and rate of its buildup is much more rapid.
Casual Organism :Cercosporidium personatum, Cerocospora arachidicola
Disease Cycle:The fungus survives in the conidial or mycelial state on diseased plant debris and on the shells of the seed. Conidia are disseminated through wind. These germinate by germ tubes and cause infection directly or through stomata.
Epidemiology:Warm and moist weather conditions encourage development of epidemics. Optimum temperature is 24-28ºC with a period of 3 days of high humidity. The incubation period is 8-15 days.
- Plant disease debris should be burnt.
- Seed dressing with a suitable fungicide like Benlate and Vitavax (2 gms/kg of seed).
- Foliage spray with Bordeaux Mixture (4:4:50), Dithane M-45 (0.2%), Benlate and Bavistin (0.1%) gives good results.
- Early maturing and spreading type varieties are less liable to attack of the disease.