Temporal and spatial epidemic development of groundnut rust (Puccinia arachidis Speg.) as a function of altered date of sowing. (45)

Abstract

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