Latest Guide to Common Rice Disease Prevention and Control Techniques

1. Rice blast

Rice blast, also known as rice fever, can be divided according to the damage period and plant part into seedling blast, leaf blast, neck blast, branch blast, grain blast, and so on.

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 node, then gradually extend around the node, making the diseased part black and easily broken. Early occurrence forms withered white heads. Occurrence on only one side causes the stem to bend.

Neck blast: initially forms small brown spots, and after expansion turns the panicle neck brown, also causing withered white heads. Late occurrence causes blighted grains. Damage to branches or the panicle axis causes unfilled spikelets.

Grain blast: produces brown elliptical or irregular spots, which can make the rice grain black. Some glumes show no symptoms, while the sterile lemmas are damaged and turn brown, causing the seed to carry the pathogen.

Control methods: use disease-resistant varieties; fertilize rationally, increase organic fertilizer and phosphorus-potassium fertilizer; irrigate and drain scientifically; 2-3 days before heading, use 75-100 ml of 40% Fuji No. 1 EC or 100 g of 20% tricyclazole wettable powder per mu mixed with 20 g Jiumiao seaweed acid iodine, add 50-75 kg water and spray, then spray once more after 7-10 days.

2. Rice bacterial leaf blight

Symptoms: mainly occurs on leaves and leaf sheaths. In the initial stage, semi-transparent yellow small spots appear on the leaf margin, then develop along one side 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 margin of fresh lesions secretes turbid water droplets or honey-yellow bacterial ooze, which dries into hard particles that easily fall off.

Control methods: use disease-resistant varieties; soak seeds in 50-fold 1% zhongshengmycin solution for 24 hours for disinfection; cultivate disease-free strong seedlings; 7-10 days before transplanting, spray 20% yekuning wettable powder at 500-fold per mu mixed with Saisheng seaweed acid iodine. After strong 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 then gradually expand into elliptical or cloud-like shapes; when severe, several lesions merge to form large lesions, appearing as irregular cloud-like spots, often causing leaves to yellow and die; when leaf infection develops quickly, the lesions are dirty green and the leaves rot quickly. When the stem is damaged, it often cannot head, and under high temperature a layer of white powdery mold forms on the lesions.

Control methods: remove sclerotia to reduce inoculum sources; do not apply excessive nitrogen fertilizer, increase phosphorus-potassium fertilizer; plant at reasonable density, irrigate reasonably, irrigate frequently with shallow water, dry the field moderately, and reduce field humidity; from row closure to before maturity, spray 30% jiajunhejing WP at 800-1 000-fold mixed with Saisheng seaweed acid iodine 3-4 times.

4. Rice brown spot disease

Symptoms: when seeds are damaged at the bud stage, the coleoptile turns brown, the bud fails to emerge, and the cotyledons die. When leaves and leaf sheaths are affected at the seedling stage, the lesions expand and merge into strips, and when there are many lesions the seedlings die. On adult plant leaves, the lesion edges are brown, and in severe cases they merge into irregular large spots. Diseased leaves dry from the leaf tip inward, are damp brown, and black mold grows on dead seedlings. Leaf sheath infection is water-soaked, then becomes an irregular large spot with a grayish brown center. Damage to the panicle neck and branches makes the affected parts dark brown and causes panicle blight. Grain infection is grayish black and expands to the whole grain, causing blighted grains. When the climate is humid, black velvety mold grows on the diseased part.

Control methods: disinfect good seeds, increase Chongzhidao soil mix ratio, avoid excessive nitrogen fertilizer; spray 20% jinggangmycin wettable powder at 1000-fold mixed with Huaguo Yisheng Guoneng multi-element.

5. Rice stripe virus disease

Symptoms: in the early growth stage of rice, the central leaf and the first leaf below the central leaf show chlorotic yellow striped lines, which gradually expand into irregular long yellow stripes; the central leaf twists, curls, or dies, forming a “false dead heart”, and finally the whole plant dies; in the later growth stage of rice, the flag leaf and flag leaf sheath become chlorotic yellow or yellow-white, and diseased panicles are often tightly wrapped in the leaf sheath and difficult to emerge, forming blighted panicles, so the rice cannot set seed normally, greatly affecting rice yield.

Control methods: plow and plant to reduce the overwintering population of small brown planthoppers; clear weeds along roadsides and field edges; use disease-resistant varieties; increase Defuer drip irrigation topdressing fertilizer, avoid excessive nitrogen fertilizer; during the seedling field period and early main field period, use 50 kg of 1000-fold 50% metolcarb per mu, or 2 kg of 2% yechensan powder mixed with water and spray.

6. Rice bacterial leaf streak

Symptoms: mainly damages leaves, sometimes also leaf sheaths. The lesions occur between leaf veins, initially as dark green water-soaked small spots, and after expansion are limited by the leaf veins, forming dark green streaks that are transparent against light, about 10 mm long and about 1 mm wide; the lesion surface often secretes many yellow bacterial ooze, which after drying forms yellow gum-like small particles.

Control methods: disinfect good seeds; spray 500-600-fold 50% amobam mixed with Huaguo Yisheng Guoneng multi-element; start 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 more slender than healthy seedlings, have narrow and long leaves, and poorly developed roots.

Disease characteristics: the pathogen overwinters on diseased rice straw or the seeds themselves carry the pathogen, becoming the primary infection source. The pathogen invades the stem base of seedlings through wounds and spreads through irrigation water and rainwater.

Control methods: 1. Use disease-free varieties and avoid saving seeds from diseased fields and nearby fields; 2. disinfect seeds, using carbendazim, Quanbaike, strong chlorine essence, etc. 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 expose a light yellow mass, namely the pathogen spore ball.

Control methods: 1. choose disease-resistant varieties; 2. disinfect seeds, same as rice blast and sheath blight; 3. in combination 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. Early symptoms are small dark brown 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.

(2) Panicle: the young panicle inside the leaf sheath dies partially or completely, becoming a blighted panicle; in milder cases it appears as half-emerged panicles with neck enclosure. When humid, powdery mold grows on the diseased part; peeling open the flag leaf sheath reveals mycelium and powdery mold, which are the pathogen of this disease.

Control methods: select and breed disease-resistant good varieties; disinfect seeds; when necessary, spray 50% benomyl WP at 1 500-fold mixed with Saisheng seaweed acid iodine. Spray once every 15 days, 1-2 times continuously.

10. Rice seedling rot

Seedling rot is the general term for seed rot, bud rot, and seedling death. One type is caused by physiological factors, and the other is infectious seedling rot caused by fungi.

(1) Physiological seedling rot: after sowing, the seeds do not germinate and gradually turn black and rot, namely seed rot; before rooting, the young buds stand askew with black heads and black roots, then rot and die, namely bud rot. Seedlings die at the 2-3 leaf stage, namely seedling death.

(2) Infectious seedling rot

① Bacterial wilt-type seedling death: the leaf tips of diseased plants first stop guttation, then the central leaf suddenly wilts and rolls into a tube, followed by the lower leaves rapidly losing water, wilting, and rolling into tubes, until the whole plant becomes dirty green and dies; the root system of diseased plants is dark and root hairs are sparse.

② Yellow wilt-type seedling death: starting from the lower leaves, from the leaf tip to the leaf base gradually turning yellow, spreading upward to the central leaf, and finally the plant base turns brown and softens until the whole plant becomes yellow-brown and dies; the root system of diseased plants is dark, root hairs are sparse, and roots are easy to pull up.

Control methods: use good seeds and disinfect them; sow in a timely manner when clear weather occurs; apply Defuer drip irrigation topdressing fertilizer and increase phosphate fertilizer; manage water scientifically and regulate temperature differences: keep the seedbed moist during the bud stage to ensure sufficient oxygen in the soil; from the one-leaf-one-heart to three-leaf stage of seedlings, spray promptly when leaf tips stop guttation and sporadic leaf rolling appears in the field, using 1000-fold 50% dexon wettable powder mixed with Huaguo Yisheng Guoneng multi-element; if the disease is severe, appropriately increase the dosage.

11. Rice bacterial brown spot

Symptoms: leaf lesions are initially brown water-soaked small spots, then gradually expand, and in the later stage the center of the lesion turns grayish brown, with local leaf necrosis. Affected leaf sheaths mostly occur on the upper leaf sheath, initially as red short strips, then merging into irregular large spots, and the tissue in the center of the lesion also turns grayish brown and necrotic. Peeling open the leaf sheath reveals dark brown streaks on the stem. Before heading, if the flag leaf sheath is severely affected, the panicle often cannot emerge.

Control methods: in old diseased areas, before or after the arrival or passage of typhoons and rainstorms, use 500-fold 70% yekujing (also called shakujing) suspension concentrate per mu mixed with Saisheng seaweed acid iodine, and immediately spray the whole field once on diseased fields or susceptible varieties, especially fields flooded by floods. Generally spray once every 7-10 days; for early-onset cases spray twice, and for late-onset cases spray once.

12. Rice kernel smut

Symptoms: at the seedling stage, pale yellow chlorotic spots appear at the leaf tips and gradually develop toward the base, forming yellowed mosaic leaf tissue, after which the whole leaf turns yellow, rolls upward longitudinally, and withers and droops. Plants are stunted, do not tiller, and have short small root systems. Those infected after tillering cannot head and set seed normally. Those infected after jointing head late, have small panicles, and set seed poorly.

Control methods: use disease-resistant varieties and disinfect them, strengthen seed quarantine; practice paddy-upland rotation; increase Chongzhidao soil mix ratio, do not apply excessive nitrogen fertilizer; use 1000-fold 25% triadimefon WP mixed with Huaguo Yisheng Guoneng multi-element, and apply chemical control once at the initial flowering stage, full flowering stage, and grain-filling stage in production fields. After the female parent is threshed, most diseased grains become tailings; these tailings should be collected and burned.

13. Rice dwarf virus disease

Symptoms: mainly damages grains. After grains are infected, symptoms are initially not obvious and are no different from normal grains; symptoms appear in the middle and late stages of the disease. There are 3 types of symptoms:

The grain color is normal, the glumes open naturally, exposing black granular material, light in weight when pressed by hand; in rainy and humid weather the diseased grains rupture and release black powdery chlamydospores. The grain color is normal, the outer glume back line near the sterile lemma cracks, revealing red or white tongue-like material, and the glume shell is attached with black powder. The grain color is dark green, resembling green blighted grain externally, does not crack, feels soft when pinched, and turns black when soaked in clear water.

Control methods: plant in contiguous fields, harvest in contiguous fields, and promptly control the green leafhopper. Eliminate weeds such as Alopecurus aequalis to reduce overwintering insect sources. Once diseased plants are found, pull them out promptly. Actively control virus-transmitting insects.