Temporal and spatial epidemic development of groundnut rust (Puccinia arachidis Speg.) as a function of altered date of sowing

Temporal and spatial spread of groundnut rust (Puccinia arachidis Speg.) on groundnut sown at different dates over three seasons and two years were mo nitored to identify the dates of sowing that restricts apparent infection r ate to a low level. From disease severity recorded at 10-day intervals, r w as calculated using logistic and Gompertz transformations. Dates of sowing which had low infection rates in the Gompertz model (0.02 units) or less pe r day indicated slow progress of the disease. Although both models effectiv ely linearized the disease proportions, Gompertz was more suitable with low er variation in infection rates, standard errors of estimate, and higher co rrelation coefficient. Late sowing in the rainy season caused lower disease severity whereas in the winter and summer season, early sowing minimized t he severity of disease incidence.