Advances in the Integrated Approach of Diseases Management in Case of Brown Leaf Spot Caused by Helminthosporium oryzae

Abstract:

Brown leaf spot caused by Helminthosporium oryzae (syn. Bipolaris oryzae) is a major fungal disease of rice causing yield loss and grain quality degradation in both irrigated and rainfed systems. Brown leaf spot is very severe in deficient soil nutrients, high humidity, continuous leaf wetness, and stressed environment. Chemical fungicides have been used traditionally for control of this disease but now the use of fungicide has become unsustainable owing to development of fungicide resistance, environmental pollution, and production cost. Integrated disease management (IDM) has thus become an effective approach for sustainable control of brown leaf spot disease. This review discusses recent developments in IDM of brown leaf spot through the integration of cultural, biological, chemical, and resistant host. Balanced fertilization, crop rotation, residue management, proper plant density, and irrigation schedule can minimize the incidence of this disease effectively. Use of resistant or tolerant rice cultivars has always been an economical approach. Systemic fungicide seed treatment and careful foliar application of contact and systemic fungicides prove to be an effective measure in disease management. Use of biological control agents like Trichoderma spp., Bacillus spp., and Pseudomonas fluorescens is proving successful through their ability to suppress pathogens and increase the plant's defense mechanism. Advances in molecular diagnostic methods, remote sensing, disease forecasting and models, and precision agricultural techniques can aid in early identification and control measures. Moreover, the use of integrated nutrient management, silicon supply, and plant growth promoting rhizobacteria can ensure good plant health and help build resistance against infection. The present review suggests that the combination of resistant varieties, proper nutritional status of plants, biological control agents, cultural measures, and need-based application of fungicides provides a sustainable, cost-effective, and environmental-friendly approach to disease management of brown leaf spot. Further work should be aimed at developing strategies of disease management resilient to climate change and the development of molecular breeding tools for long-lasting resistance.