Comparing nonlinear models in describing disease progress curve of cocoa black pod

Cocoa black pod caused by Phytophthora palmivora is one of the major disease problems facing by the cocoa growers around the world including Malaysia. The losses due to this disease exceed $400 million worldwide and the economic solution to control the losses is using resistant cocoa clones against black pod disease. It is important to understand the disease progress curve over time to determine the resistant level of the cocoa clones against the disease. Normally, the detached pod test was carried out in laboratory to study the disease progress curve and determine the resistant level of the cocoa clones against the disease. The objective of this paper is to analyse the disease progress curve with several nonlinear models such as exponential model, monomolecular model, logistic model and Gompertz model. Then, the best fitted model was selected to describe the disease progress curve based on the measurement of the goodness of fit tests such as the lowest Akaike Information Criterion (AIC) and lowest Bayesian Information Criterion (BIC). Four different cocoa clones, namely KKM4, KKM5, QH1003 and BR25 were tested for the resistant level against the cocoa black pod. The disease severity used in describing the disease progress curve was calculated as proportion of lesion area over the pod surface area. The data was recorded over six days after the pod was inoculated with Phytophthora palmivora. The results showed that the rate of disease severity could be fitted to a Gompertz curve as it has the lowest AIC and BIC. This curve is useful for predicting the disease severity and used to determine the resistance level by estimating the area under disease progress curve.Cocoa black pod caused by Phytophthora palmivora is one of the major disease problems facing by the cocoa growers around the world including Malaysia. The losses due to this disease exceed $400 million worldwide and the economic solution to control the losses is using resistant cocoa clones against black pod disease. It is important to understand the disease progress curve over time to determine the resistant level of the cocoa clones against the disease. Normally, the detached pod test was carried out in laboratory to study the disease progress curve and determine the resistant level of the cocoa clones against the disease. The objective of this paper is to analyse the disease progress curve with several nonlinear models such as exponential model, monomolecular model, logistic model and Gompertz model. Then, the best fitted model was selected to describe the disease progress curve based on the measurement of the goodness of fit tests such as the lowest Akaike Information Criterion (AIC) and lowest Bayesi...