COMPARISON OF THE GOMPERTZ AND LOGISTIC EQUATIONS TO DESCRIBE PLANT-DISEASE PROGRESS

The Gompertz transformation effectively linearized 113 disease progress curves of 9 pathosystems. The Gompertz model avoided the curvilinearity commonly associated with logistically transformed values. Estimation of epidemic rate, projection of future disease severity and determination of initial disease were more accurate with the Gompertz than with the logistic model. Since many pathosystems have asymmetrical disease progress curves, transformations other than the logistic may be more appropriate to estimate epidemic parameters.