Identification and Control of Rice Leaf Blast Symptoms

What is rice leaf blast? How to control it?

Rice leaf blast is a common disease, and farmers should identify it carefully.

This disease occurs on the leaves of seedlings after the three-leaf stage or on adult plants, generally breaking out heavily from the tillering stage to the jointing stage. The lesions on the leaves often differ in shape, size and color due to differences in weather and varietal disease resistance, and can be divided into four types: chronic, acute, white-spot and brown-spot, among which the first two are the most important in terms of damage. Chronic lesions are diamond-shaped or spindle-shaped, generally 1 to 1.5 cm long and 0.3 to 0.5 cm wide, red-brown to gray-white, with necrotic lines at both ends. Acute lesions are nearly round or irregular, dark green, with dense gray mold on the underside of the lesion. The appearance of acute lesions can be regarded as a precursor to a major field epidemic of the disease.

What is rice leaf blast? How to control it?

Rice leaf blast control techniques

1. Select disease-resistant varieties, and pay attention to variety combination and rotation.

2. Treat rice seeds before sowing: soak seeds with 45% prochloraz; apply pre-transplanting fertilizer and pre-transplanting pesticide before transplanting: one week before transplanting, apply 3-5 kg of urea per mu to the seedling field to enhance plant disease resistance, and apply it together with the pre-transplanting pesticide for controlling leaf blast as well as borers and planthoppers. You can also soak the seedlings in a 20% tricyclazole wettable powder solution for 5 minutes, take them out, pile and cover them for 30 minutes, and then transplant.

3. Reasonable fertilizer and water management: apply sufficient base fertilizer, apply topdressing early, apply appropriate nitrogen in the middle stage to control seedling growth, and supplement fertilizer in the later stage according to seedling condition. Avoid applying too much nitrogen fertilizer or applying it too late, and focus on increasing the application of phosphorus and potassium fertilizers. Water management should follow the principles of shallow-water transplanting, deep-water greening, thin-water tillering, and drying the field once enough tillers have formed.

4. Chemical control. Leaf blast should be discovered and controlled early; starting from the tillering stage, if a disease center is found or acute lesions appear on the leaves, chemical control should be carried out promptly.

Common pesticides: 6% kasugamycin wettable powder 30-40 grams per mu per application, or 75% tricyclazole wettable powder 30-40 grams per mu per application, or 40% Fuji-one emulsifiable concentrate 100 ml per mu per application. Dilute any one of the above pesticides with 45-60 kg of water and spray for control, then control again after 6-8 days. If it rains within 4 hours after spraying, it must be re-sprayed in order to achieve the ideal control effect.