Relative performance of five forecasting schemes for potato late blight (Phytophthora infestans) I.: Accuracy of infection warnings and reduction of unnecessary, theoretical, fungicide applications

The Smith Period, Negative Prognosis, Blitecast, Sparks and NegFry forecasting schemes for potato late blight were evaluated over a 6-year period at five locations representing a range of blight risk situations. Frequent measurements were made by in-field meteorological stations and untreated, blight susceptible, potatoes in small plots were regularly assessed for. symptoms of the disease. Although the Smith Period was the most reliable scheme (warnings rarely in error) it often gave too long an advanced warning of an eventual disease outbreak; NegFry was the most accurate scheme assuming an ideal warning of 10 days was required by growers. (C) 2002 Elsevier Science Ltd. All rights reserved.