Detailed Guide to Common Rice Disease Prevention and Control Methods
1. Rice Blast
Rice blast, also known as rice fever, can be divided into seedling blast, leaf blast, neck blast, branch blast, and grain blast according to the period and site of damage.
Seedling blast: the base is grayish-black, the upper part turns brown, curls and dies; when humidity is high, the diseased part produces a large amount of grayish-black mold. Leaf blast can occur throughout the entire growth period. Damage is more severe from tillering to jointing stage.
Node blast: small brown spots appear on the rice nodes, then gradually extend around the node, turning the diseased part black and making it easily broken. Early occurrence results in withered white heads. Occurrence on only one side causes the stem to bend.
Neck blast: initially forms small brown spots, which after spreading turn the neck of the panicle brown and also cause withered white heads. Late occurrence results in blighted grain. Damage to branches or the panicle axis causes unfilled spikelets.
Grain blast: produces brown oval or irregular spots that can turn the rice grain black. Some glumes show no symptoms, but the sterile lemmas are damaged and turn brown, causing the seeds to carry the pathogen.
Prevention and control methods: select disease-resistant varieties; fertilize reasonably, increase organic fertilizer and phosphorus-potassium fertilizer; irrigate and drain scientifically; 2-3 days before heading, spray each mu with 75-100 ml of 40% Fuji No. 1 emulsifiable concentrate or 100 g of 20% tricyclazole wettable powder mixed with 20 g of Jiumiao seaweed acid iodine, add 50-75 kg of water and spray, then spray again after 7-10 days.
2. Rice Bacterial Leaf Blight
Symptoms: mainly occurs on leaves and leaf sheaths. Initially, semi-transparent yellow small spots appear on the leaf margins, then develop along one or both sides of the leaf veins or along the midrib into wavy yellow-green or gray-green lesions; the boundary between the diseased part and the healthy part is obvious; after several days, the lesions turn grayish-white and curl inward. When the air is humid, the leaf margins of fresh lesions secrete turbid water droplets or honey-yellow bacterial ooze, which dries into hard particles that easily fall off.
Prevention and control methods: select disease-resistant varieties; soak seeds in 50-fold dilution of 1% Zhongshengmycin for 24 hours for disinfection; cultivate disease-free strong seedlings; 7-10 days before transplanting, spray each mu with 500-fold dilution of 20% Yekuning wettable powder mixed with Saisheng seaweed acid iodine. After heavy wind and rain, flooded rice fields should be promptly sprayed with Jiumiao seaweed acid iodine for protection.
3. Rice Sheath Blight
Symptoms: the leaf sheath produces dark green water-soaked small spots with blurred edges, which gradually expand into oval or cloud-like shapes. In severe cases, several lesions merge to form large lesions, appearing as irregular cloud-like patterns, often causing leaves to turn yellow and die; when the leaf is affected rapidly, the lesions appear dirty green and the leaves rot quickly. When the stem is damaged, it often cannot head; under high temperature conditions, a layer of white powdery mold forms on the lesions.
Prevention and control methods: remove sclerotia to reduce the source of inoculum; do not apply excessive nitrogen fertilizer, increase phosphorus-potassium fertilizer; plant at a reasonable density, irrigate reasonably, irrigate frequently with shallow water, dry the field moderately, and reduce field humidity; from row closure to before maturity, spray 800-1,000-fold dilution of 30% JUNHEJING WP mixed with Saisheng seaweed acid iodine 3-4 times.
4. Rice Brown Spot
Symptoms: when seeds are damaged at the bud stage, the coleoptile turns brown, the bud fails to emerge, and the cotyledons die. When seedlings' leaves and leaf sheaths are affected, the lesions expand and merge into strips; when there are many lesions, the seedlings die. On adult plant leaves, the lesions have brown edges and, in severe cases, merge into irregular large spots. Diseased leaves dry from the tip inward, appearing damp brown, and black mold grows on dead seedlings. On leaf sheaths, the disease is water-soaked, then becomes irregular large spots with a grayish-brown center. When the panicle neck and branches are affected, the damaged parts are dark brown, causing the panicle to wither. When grains are affected, grayish-black discoloration spreads to the whole grain, causing blighted grain. When the climate is humid, black velvety mold grows on the lesions.
Prevention and control methods: disinfect good seeds, increase the application of Chongzhidao soil mix, avoid excessive nitrogen fertilizer; spray 1,000-fold dilution of 20% Jinggangmycin wettable powder mixed with Huaguo Doctor Guoneng multi-element.
5. Rice Stripe Leaf Blight
Symptoms: in the early growth stage of rice, chlorotic yellow streak lines appear on the heart leaf and the first leaf below the heart leaf, then gradually expand into irregular long yellow stripes; the heart leaf twists, curls, or dies, forming a "false dead heart," and finally the whole plant dies; in the late growth stage of rice, the flag leaf and flag leaf sheath become chlorotic and turn yellow or yellowish-white, and diseased panicles are often tightly wrapped inside the leaf sheath and difficult to emerge, forming a withered pregnant panicle, preventing the rice from setting grain normally, which greatly affects rice yield.
Prevention and control methods: plow and plant to reduce the overwintering population of the small brown planthopper; clear weeds along roadsides and field edges of ditches; select disease-resistant varieties; increase the application of Defuer drip irrigation topdressing fertilizer, avoid excessive nitrogen fertilizer; during the seedling field period and early main field period, spray each mu with 50 kg of 1,000-fold dilution of 50% metolcarb, or 2 kg of 2% MIPC powder plus water.
6. Rice Bacterial Leaf Streak
Symptoms: mainly damages leaves, sometimes also leaf sheaths. Lesions occur between leaf veins, initially as dark green water-soaked small spots, which after expansion are limited by leaf veins and form dark green streaks, transparent when held against light, about 10 mm long and about 1 mm wide; the surface of the lesions often secretes abundant yellow bacterial ooze, which dries into small yellow gum-like particles.
Prevention and control methods: disinfect good seeds; spray 500-600-fold dilution of 50% amobam mixed with Huaguo Doctor Guoneng multi-element; begin spraying at the heading stage, then apply once more after 7 days.
7. Rice Bakanae Disease
Symptoms: this disease can occur from the seedling stage to the heading stage. Diseased seedlings are pale yellow-green in color, grow taller and weaker than healthy seedlings, have narrow and long leaves, and poorly developed roots.
Disease characteristics: the pathogen overwinters on diseased rice straw or is carried by the seeds themselves, becoming the primary infection source; the pathogen enters the base of seedling stems through wounds and spreads through irrigation water and rainwater.
Prevention and control methods: 1. Select disease-free varieties and avoid saving seeds from diseased fields or nearby fields; 2. Disinfect seeds; carbendazim, Quanbaik, and strong chlorine essence can be used for disinfection treatment, and the key lies in disinfection; 3. Once diseased plants are found, pull them out immediately.
8. Rice False Smut
Damages individual grains; initially, mycelium forms inside the grain and gradually enlarges, causing the lemma and palea to open and exposing a pale yellow mass, namely the pathogen's spore ball.
Prevention and control methods: 1. Select disease-resistant varieties; 2. Disinfect seeds, the same as for rice blast and sheath blight; 3. Combined with sheath blight control, spray Jinggangmycin 3-4 times from row closure to before maturity.
9. Rice Sheath Rot
Symptoms (1) Leaves: sheath rot mostly occurs on the flag leaf sheath at the booting stage of rice. The initial symptoms are dark brown small spots with blurred edges, which later gather into cloud-like lesions resembling tiger stripes; the lesions continue to expand to most of the leaf sheath.