symptom
Also known as rice leaf blight, brown spot disease, narrow spot disease. It occurs in all rice regions of the country. At the beginning of the disease, the leaves were brown dots, and they spread along the veins on both sides. They were reddish-brown or purple-brown in the surroundings. The center was gray and brown with short and thin lines and spots. The disease-resistant varieties had short lesion lines, narrow lesions, and deep colors. When the disease is severe, the lesion grows with streak, leading to premature leaf blight. Leaf sheath infections mostly appeared from the base of thin streak, and later developed into purple-brown plaques. In severe cases, all leaf sheaths may turn purple, and the upper leaves die. The neck and branch stems were dark to brownish at the beginning of the disease, showing a slight purple color. Severe disease caused the neck to die and the difference between the ear and ear was noticed. The grain damage occurred mostly on the surface of the shield or grain, showing a brownish brown stripe.
pathogen
Cercospora oryzae Miyake = C. janseana Miyake called rice spores of the genus Aspergillus spp. Conidiophores solitary, or 3-5 clustered, several separated, size 34.3-58.84.3-4.8 (μm), terminal conidia, conidia pale olive or colorless, short whitish There are more than 3-4 separations, sizes 25.7-34.34.3-5.2 (μm). The sexual state is Sphaerulina oryzae Hara, known as the rice subglobules, belonging to the phylum Ascomycotina.
Transmission routes and conditions
The diseased seed or disease carrier is the main primary infection source, and the pathogen can survive on rice seeds until July of the following year. The pathogens on rice straw differ greatly in their viability due to their different storage sites. They only survive for 5 days when they are buried deep in grass ponds or manure. In the following year, conidia are produced under suitable conditions and spread to the rice fields with wind and rain, causing the disease. The diseased strain produces conidia for reinfection. The bacteria can develop between 6-33°C, and the optimum temperature is 25-28°C. The disease mainly occurs at the heading stage. Phosphorus deficiency, poor growth, heavy disease; long-term deep-seated disease; heavy rain, high temperature and favorable conditions occur. Single-season late rice is generally heavier.
Control methods
1 Treat sick straw and select disease-resistant varieties. 2 Do a good job of fertilizer and water management. Increase organic fertilizers as base fertilizers, avoid partial nitrogen fertilizers, reasonably apply phosphorus and potash fertilizers, and increase plant resistance to disease; shallow water irrigation, timely field drying, promote rice root growth, enhance suction fertility, and prevent premature aging.
3 shallow water ground irrigation, timely field.
4 break to full head every 667m2 (1 mu) with 50% carbendazim WP 125 ~ 150g, or 70% thiophanate wettable powder 50g, or 50% benzene WP 75g, watered 75kg spray .
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