Evaluation of fungicides against late blight (Phytophthora infestans) on susceptible and moderately resistant potato cultivars

摘要

Late blight caused by oomycete pathogen Phytophthora infestans (Mont.) de Bary, is one of the most destructive diseases of potato and results in yield losses up to 95% in epidemic conditions. The pathogen is polycyclic in nature and completes many cycles in a crop season. Management strategies for its effective control include use of host resistance, chemicals, forecasting, sanitation and even disease escape (2, 10). Although the best strategies to combat this menace is to breed for host resistance,yet the experience so far has shown that resistance in potato varieties break down within a decade. Therefore, only suitable alternative left over is use of fungicides. However, the pathogen has shown a remarkable capacity for change with respect to hostgenotype and fungicides. As a result, disease control requires regular application of fungicides at high rates and short intervals throughout the growing season. It is therefore, important to enhance host resistance with fungicides. The use of cultivarswith durable resistance combined with scheduled applications of protective fungicides has been reported as useful for managing late blight, as well as for other diseases. Regarding effectiveness of mixture of fungicides and their rotation strategies, experimental data are limited (4). In the present study different treatment combinations were assessed on two potato varieties having different level of resistance to know their efficacy in the management of late blight.