Evaluation of PLANT-Plus, a decision support system for control of early blight on potatoes in South Africa

Abstract

Early blight is a major foliar disease of potatoes in most potato growing regions of the world. Numerous forecasting models have been developed and evaluated for the control of early blight on potatoes; however, prior to the development of the PLANT-Plus early blight forecaster none were applicable to South African conditions and cultivars. Field trials, conducted in spring and fall at one location and in fall at another, were used to evaluate the model. These trials compared the efficacy of fungicide programmes applied according to PLANT-Plus with a conventional calendar-based spray programme for control of early blight in South Africa. The PLANT-Plus early blight decision support system reduced the number of fungicide applications without negatively affecting yield or returns. Area under the disease progress curve-values were not significantly different for the PLANT-Plus and conventional treatments, but both were significantly lower than those of the unsprayed control. The PLANT-Plus early blight forecasting model holds great potential for use in the South African potato industry, but must be incorporated into the existing PLANT-Plus late blight forecaster in order to be more cost-effective and have multipurpose applicability.