Relationship Between Yield Loss and Severity of Early and Late Leafspot Diseases of Peanut

Levels of groundnut leafspot ( Cercospora arachidicola [ Mycosphaerella arachidis] or Cercosporidium personatum [ M. berkeleyi]) were adjusted by applying fungicides of differing effectiveness. Disease levels 2-3 wk before harvest were related to dry pod yield. In studies conducted for 4 yr, data indicated that for Florunner groundnuts with a yield potential of c. 4400 kg/ha, yield was reduced by an av. 57 kg/ha for each percent of defoliation. Groundnuts could tolerate low levels of infection, but all levels of defoliation resulted in yield loss. No difference in loss-producing potential (yield loss/unit of disease) was observed between the 2 spp. since similar levels of disease caused similar losses. However, slopes of regression lines did differ significantly when years were compared.