July 2015. Spots on leaves and spots/rot on fruit in Nigeria. Members were asked to comment, but there was no response.
A member wrote: If these pictures were sent from the Pacific, I would say that the yellow spots were Corynespora, but no idea what’s present in Nigeria. Same with the lesions on the fruit, either Corynespora or Colletotrichum, most probably secondary to damage.
Microscopic examination and/or isolation is the only way to answer the question; otherwise, it’s a guess.
Members also said that the symptoms were similar to what in Australia is called brown spot – caused by the fungus Corynespora cassiicola. As suggested, the only way to be sure will be to examine under a microscope and examine spores.
In the field, a quick check can be made by using a x10 magnifying glass. Look at the lesions on the underside of the leaf for black fungal threads in some of the larger lesions. These dark threads are the conidia (or spores) and conidiophores (the structure on which the spores are produced ). This fungus is very active when conditions are wet and warm. In Australia, we may need to apply fungicides on a regular basis to keep the disease under control.
A very good online reference for brown spot is the PaDIL site – http://www.padil.gov.au/pests-and-diseases/pest/main/136590