Knowledge on controlling rice blast disease

Rice blast is one of the most dangerous diseases in rice plants, causing significant damage to yield and quality in many rice-growing regions in Vietnam. The disease can appear at almost all growth stages, from seedlings to flowering, with the most critical stages being panicle initiation and heading. Early identification and the application of effective prevention measures are key factors in helping farmers protect their crops.

Knowledge on preventing and controlling rice blast disease

Causes of the disease

Rice blast is caused by the fungus Magnaporthe oryzae. This fungus spreads very quickly via wind and water. Fungal spores survive on stubble residue, weeds, or in the soil, then infect rice plants when conditions are favorable. The fungus thrives in humid weather conditions, temperatures between 20–28°C, cloudy skies, heavy fog, or prolonged drizzling rain. Fields with high nitrogen fertilization, dense planting, and susceptible varieties often face a higher risk of severe infection.

Identification symptoms

Rice blast can damage many parts of the rice plant: On leaves: Diamond-shaped lesions appear, with gray centers and brown borders. When the disease is severe, lesions merge, causing the leaves to dry up. On the panicle neck (neck blast): This is the most dangerous form. The lesion causes the panicle neck to constrict and turn brownish-black, leading to completely empty grains. On stems and nodes: Causes stem rot, making the plant prone to lodging. Early detection of the disease at the leaf stage is crucial for prevention and control, avoiding the spread to the panicle neck.

Impact of the disease

Rice blast can reduce yields by 20–50%, or even lead to total loss if a strong outbreak occurs during the heading stage. In addition, rice quality is affected due to an increase in empty and shriveled grains. The disease develops rapidly and is difficult to control without timely preventive measures.

Principles of prevention and control

Prevention is primary; treatment must be timely and correct. Apply an integrated approach combining cultivation, varieties, and chemical measures to achieve high and sustainable efficiency.

Cultivation measures

Choosing resistant varieties: Using rice varieties with good resistance to rice blast is a long-term and effective solution. Planting in the right season: Avoid planting during weather periods favorable for fungal development. Proper density: Do not plant too densely to ensure field ventilation and reduce humidity. Balanced fertilization: Limit excessive nitrogen, increase potassium and organic fertilizer to boost plant resistance. Proper water management: Maintain stable water levels, avoiding fields being too dry or too wet for long periods. Field sanitation: Clean up residues after harvest, plow under stubble to destroy disease sources.

Biological measures

Currently, many biological products containing antagonistic microorganisms such as Trichoderma fungi are used to limit the development of pathogenic fungi. This is an environmentally friendly direction, safe for producers and consumers.

Chemical measures

When the disease appears or there is a risk of an outbreak, crop protection products must be used at the right time and in the right way: Spray preventively when weather conditions favor disease development or when the first lesions are detected. Use specific rice blast treatments as recommended by the agricultural sector. Spray at the correct dosage, ensuring enough water and even coverage on the leaves. Do not abuse chemicals to avoid drug resistance and environmental pollution. Particularly, during the panicle initiation and heading stages, preventive spraying for neck blast is needed at the right time (5–7 days before and after heading) to protect yield.

Monitoring and disease forecasting

Farmers should visit their fields regularly, monitor weather developments and pest situations for early detection. Additionally, they should update pest forecast information from specialized agencies for timely handling measures.

Important notes

Do not apply nitrogen late when the rice has reached the jointing or panicle initiation stage. Do not spray when it is about to rain or in intense sunlight. Rotate crops to limit disease source accumulation in the soil. Use chemicals according to the "4 rights" principle: right product, right dose, right time, right way.

Rice blast is a major threat to rice production, but it can be completely controlled if proper technical measures are applied. Combining synchronized solutions from varieties and cultivation to proper chemical use will help minimize damage. In the context of climate change causing complex weather developments, farmers need to be more proactive in prevention and control to ensure sustainable yield and economic efficiency./.