Interactions between Cercospora arachidicola and Phoma arachidicola, and their effects on defoliation and kernel yield of groundnut

Cercospora arachidicola and Phoma arachidicola spread independently on groundnuts when leaf area was not limiting, but where C. arachidicola colonized leaves early, it usually spread at the expense of P. arachidicola. Juice extracted from leaflets infected with C. arachidicola and separated by thin-layer chromatography contained unidentified compounds which were not present in juice from uninfected leaflets, and prevented the growth of P. arachidicola. Cercospora leaf spot reduced photosynthesis and was the major contributor to premature leaf drop, which had an adverse effect on yield. Well blotch ( P. arachidicola ) only caused defoliation and depressed yield where there was very little Cercospora leaf spot present.