Jorge Ulises Blandón-Díaz, Department of Plant and Forest Protection, National University of Agriculture (UNA), Managua, Nicaragua, Apdo. 453, and Department of Forest Mycology and Pathology, Swedish University of Agricultural Sciences, S-750 07 Uppsala, Sweden;
Gregory A. Forbes, International Potato Center (CIP), Lima 12, Peru;
Jorge L. Andrade-Piedra, CIP, Quito, Ecuador; and
Jonathan E. Yuen, Department of Forest Mycology and Pathology, Swedish University of Agricultural Sciences
In this study, the adequacy of the late blight simulation model LATEBLIGHT (version LB2004) was evaluated under Nicaraguan conditions. During 2007 to 2008, five field experiments were conducted in three potato-production regions in northern Nicaragua. Two susceptible (‘Cal White’ and ‘Granola’) and one resistant (‘Jacqueline Lee’) potato cultivars were evaluated without use of fungicides and with three application intervals (4, 7, and 14 days) of the fungicide chlorothalonil. The simulation model was considered adequate because it accurately predicted high disease severity in susceptible cultivars without fungicide protection, and demonstrated a decrease in the disease progress curves with additional fungicide applications, similar to that observed in the plots. The model also generally predicted inadequate fungicide control, even with a 4-day spray interval, which also occurred in the field. Lack of adequate fungicide protection would indicate the need for cultivars with higher levels of durable resistance, and that farmers should consider more effective fungicides applications (higher dosages or different chemistries) if susceptible cultivars are used.