Rice blast disease, also known as rice fever, is commonly known as "burning" and "hanging". Can cause a substantial reduction in production, severely reduce production by 40% to 50%, and even no crop. The disease occurs in all parts of the country, of which the occurrence of leaf, nodal occurrence, after the occurrence can cause varying degrees of reduced production, especially the occurrence of panicle spasm or thrift, can cause white ear so that the total production.
First, symptom recognition
The whole growth period can occur. According to the different parts of the disease, diseases such as seedlings, leafhoppers, knots, panicles and grains can be formed.
1. Miao Miao: mainly occurs in the leaves of the seedling stage, the formation of brown, fusiform or amorphous lesions, and sometimes in the formation of gray green mold layer. Miao rarely occurs in our city, and special years can occur sporadically.
2. Leafhoppers: usually occur after the tillering period. Due to different species and meteorological conditions, there are four symptoms of leafhoppers, except for brown spots (resulting in disease-resistant varieties), white spots (production on susceptible leaves). In addition, acute and chronic lesions are common in the field.
1 acute lesions: when the climate is favorable, the lesions are faded green, nearly round, oval or irregular shape, lesions on the back of dense gray green mold layer.
2 chronic lesions: when the climatic conditions change, or by acute lesions, the lesions are mostly spindle-shaped, spindle-shaped, usually brown, gray in the center, and the outermost layer is yellow or pale yellow halo. Ring, a brown necrotic line at each end of the lesion. In the humid climate, the back of the lesion also produces a gray green mold layer. In later stages, multiple spots can be fused into irregularly shaped large spots, causing the entire leaf to die.
3. Frugality: Occurs mostly in the first to second sections under the flag leaf. The beginning is dark brown dots and gradually expands. The lesions can surround part or all of the joints, causing the joints to become black, and the diseased sections shrink later. Depression, so that the rice plant fracture lodging, affecting the solid, grouting, as well as the formation of white spikes.
4. Panicle and neck spasm: Occurs in the neck, cob, and branches. The lesion is dark brown at the beginning of the lesion. Afterwards, it expands to form a dark brown streak. The light affects the firmness, irrigation, and even the increase in pods. White spikes can be formed and are completely unsturdy.
5. Grain pods: Occur on husks or on cultivars, beginning with brown dots, then expanding into brown irregular spots, sometimes turning the whole grain brown, dark gray and becoming pods.
Second, pathogen identification
Rice blast disease is caused by the semi-mycotic subphylum, the caterpillar fungus, Pyricularia oryzae Cav. (Pyrus spp.) caused by fungi. There is a layer of gray green mold on the lesions, namely the conidiophore and conidia of the pathogen.
Third, the infection cycle
The germs used wintering for hyphae on sick straw and diseased seeds. In addition to sick seedlings, seedlings may develop under drought conditions. The main pathogen is wintering on diseased straw. The temperature and humidity are suitable for the following year. The pathogenic bacteria on rice straw can produce conidia and spread to rice by airflow. When the temperature and humidity conditions are suitable, germination will take place immediately, directly penetrating the epidermis and invading the leaves, causing the initial infestation, the occurrence of leaf aphid, re-infestation through airflow propagation, aggravation of leafhoppers, and reproduction of a large number of conidia, Air flow spreads, causing panicles, necks, and grains. After harvesting and threshing, the bacteria overwintered on diseased rice straw and diseased seeds.
Fourth, the incidence conditions
1. Variety resistance: There is a significant difference in resistance between different varieties. The most resistant varieties used in current production are vertical resistant varieties, and their resistance can only be maintained for a certain period of time due to physiological races. Once the inferior races become dominant In races, some species lose their disease resistance and cause disease.
2. The number of bacterial sources: If the number of diseased seeds is large, soaking and disinfection is not carried out. In particular, diseased rice straw, diseased pods and valleys are not destroyed or handled incompletely, and there are many pathogenic bacteria in winter and the incidence is heavy.
3. Meteorological conditions: If there are many rainy seasons, rainy days, and rainy days, an environment with high humidity, low temperature, and low sunshine (less sunshine hours) can reduce the disease resistance of rice, which is beneficial to the occurrence of leafhoppers; still before and after the heading period For rainy weather, there are more rainfall days and more rainfall, and the conditions of high humidity, low temperature, and low illumination are not conducive to the growth of rice, but it is beneficial to the production of spores and spore germination of pathogens, among which, the spores of high-moisture-prone pathogens germinate and invade. Low temperature and low-light conditions cause severe panicle neck, knots and grains.
4. Rice field management: If too much nitrogen fertilizer is applied, too late; often cold water irrigation, deep water irrigation, etc., will reduce rice disease resistance, can aggravate the condition.
In short, the occurrence and epidemic of rice blast are the combined effects of the above four factors.
V. Prevention methods
Take the premise of destroying the overwintering bacteria source, select the disease-resistant and high-yield varieties as the center, based on agricultural cultivation techniques, and use chemical control as an auxiliary comprehensive prevention and control strategy. Rice blast disease is a multi-circle disease mainly based on airflow propagation. Prevention and control should focus on the selection of disease-resistant varieties and chemical control.
1. Choose high-quality, high-yield, disease-resistant or disease-resistant varieties: pay attention to changes in physiological races, to prevent the loss of disease resistance of the varieties, it is best not a single species, you can use 2 to 3 disease-resistant varieties with planting.
2. Seed treatment: seed coating has better control effect on rice blast disease at seedling stage.
3. Reducing bacterial sources: timely treatment of diseased rice straw can cause diseased straw to be concentrated and burned. It is not possible to use diseased rice straw huts, cover sheds, pad pool stalks, or water inlets. The diseased seeds should be disinfected to reduce the bacteria source.
4. Strengthen field fertilizer and water management and improve disease resistance of rice: Under the premise of cultivating strong and strong broodstock, it is necessary to transplant rice stalks early and increase basal fertilization. And do early fertilizer, do not apply too much nitrogen, too late, scientific application of nitrogen, phosphorus, potassium fertilizer. Under the premise of leveling the land, reasonable shallow irrigation should be carried out. Drainage fields should be used at the end of the tillering stage, superficial irrigation should be done at the booting stage to the heading stage, so as to meet the requirements of paddy rice water requirements and contribute to rice growth and disease resistance.
5. Field investigation and chemical control: In order to accurately and promptly use drugs, the disease should first be investigated, usually before the rice tillering period, and after the rainfall, it should be carried out at the high fertilizer fields, water inlets, and manure piles (deeply growing areas) of the susceptible varieties. Investigations were conducted to observe the presence or absence of acute lesions. If there are acute lesions, they should be immediately administered with chemical control. About 10 days after application, the condition is still developing and can be applied once more. Such as leaf lice in the booting period began to occur, the condition is not heavy, combined with the prevention of pancreatic fistula for prevention and treatment. General panicle blast prevention is carried out from the end of the panicle to the beginning of the earing period. No matter whether the occurrence or weight of the pansy occurs, the chemical should be controlled once. In order to control the development of the panicle blast, it is better to conduct another chemical control at the heading stage.
The available agents are:
140% Fuji No. 1 (Inabasei) EC, 900-1125 g/ha, add water spray;
220% tricyclazole WP, 1125 to 1500 grams per hectare, 300 to 450 grams per hectare, plus water spray;
325% SPK (Cicamba) EC, 1125 to 1500 ml/ha, add water spray;
46% kasugamycin wettable powder, 450-550 per hectare, plus water spray;
Six, matters needing attention
In order to ensure the prevention effect, please pay attention to the following matters.
1 The amount of water should be enough for even spraying.
2 Grab (è¶) clear spray, because of the prevention and control of leafhoppers, panicles and necks in the rainy season, rainy days, affect the normal spraying, in order to prevent and control timely, should seize the opportunity to seize the sunny day (no rain within 4 hours ) Spraying.
3 According to many years observation of frugal occurrence is also heavier. In the control of leafhoppers and panicle blasts, all nodes of the rice plant should also be sprayed with the drug. Regardless of whether it is leafhopper, panicle-branch or frugal, it should be done as early as possible and timely, and it should be sprayed evenly and thoughtfully before it can play a preventive role.
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