How to prevent rice blight in rice planting in 2017, rice blight is one of the most important diseases of rice dry nursery, the main cause of which is low temperature, excessive temperature difference, soil alkalinity, The light is not enough, the seedlings are weak, and the amount is too large. The field symptoms are mainly characterized by the emergence of seedlings after emergence, easy to pull off, the base of the stem is rotted, the smell of rotten pears, the whole disease is heavier, and the base of the diseased plant is red. Mildew.
During the onset of rice blight, the endosperm is nearly exhausted in the 2~3 leaf stage, and the cold resistance is the worst. The daily average temperature is lower than 12~15~C, the growth is hindered, the disease resistance is significantly weakened, and the pathogen is easy to invade. At this time, if it is cold and rainy, it is most likely to cause blight. Therefore, the 2~3 leaf stage of dry nursery seedlings is the main period of blight.
Hazard symptoms of rice blight
1. Bud rot, occurs before emergence or just after emergence. The young shoots or young roots of the seedlings turn brown, and the diseased buds are distorted and rotted and die. A mildew layer is found at the base of the seed or bud.
2, needle rot, mostly occurs in the seedling period to the 2 leaf stage, the heart of the seedlings is yellow, the leaves are not unfolded, the base is brown, sometimes the brown spots on the leaf sheath, and the disease roots gradually turn yellow brown. There is a mildew layer at the junction of the seed and the base of the seedling, the stem base is weak, and it is easy to break. The seedlings in the nursery bed often cluster, and the pieces occur and die.
3, yellow withered, green and dry, mostly occurred before and after the 2.5 leaf stage of the seedlings, the tip of the diseased seedlings did not spit water, the leaves were yellow and wilting, and the burrowing rapidly expanded outward. The base and root of the seedlings were easily broken, and the leaves were snoring. . When the weather is fine, the seedlings quickly show dryness, and the heart leaves and upper leaves "snoring". The seedlings are green and the whole plant is wilting. After the transplanting, Honda appeared in a green and dead.
The cause of rice blight
1. The climatic conditions, low temperature, overcast and insufficient light are important conditions for the induction of blight, and the most affected by low temperature. Under low temperature conditions, the disease resistance of the seedlings is reduced, which is beneficial to the occurrence of diseases. The temperature is too low, which has little effect on the development and infection of pathogenic bacteria, but it is not good for seedling growth, root system is poorly developed, and the ability to absorb nutrients is reduced, which is more conducive to disease development. If the weather continues to be cold or cloudy, the soil moisture is insufficient, the seedlings are physiologically dysfunctional, and the disease is aggravated.
2, the infection cycle, rice blight is a soil-borne disease. It is caused by a variety of pathogens, mainly Fusarium oxysporum, Fusarium graminearum, Fusarium oxysporum, Fusarium solani, Fu Fusarium oxysporum and Rhizoctonia solani, and Rhizoctonia genus, and fungi such as Pythium of the genus Pythium.
Fusarium usually overwinters in the pathogens and soils of various hosts with hyphae and sputum spores. When the environmental conditions are appropriate, conidia are transmitted by airflow and infested. Rhizoctonia is overwintered by hyphae and sclerotia in host disease residues and soil, and spread by mycelium spreading between seedlings to infest.
3, seedling quality, Rhizoctonia and Fusarium and other rice bacterial pathogens are widely found in the soil, are weak parasitic bacteria, generally can live in water or soil. These pathogens are not pathogenic. They are generally not suitable for infecting robust seedlings. Only when the weather is poor and mismanagement, resulting in weak seedling growth and reduced resistance, all kinds of weak parasitic bacteria can be taken in and spread. Therefore, poor quality of seedlings, weak growth, and poor resistance to disease are the direct causes of blight.
The comprehensive prevention and control of rice blight must be based on prevention and prevention.
1. In the 1-2 leaf stage of rice seedlings, use Aolic (C. chinensis) 50ml + 15ml of garlic oil, spray 15kg with water, once every 5-7 days, and spray 2 times. In order to enhance the disease resistance of the plant, it is recommended to add 25 ml of foliar fertilizer (Wofengsu) every 15 kg of water when spraying. In the middle and late stages of the disease: Spray with Alcic Green Kelly 100ml + 15ml of Garlic Oil, spray once every 3 days, and spray 2 to 3 times.
2, carefully selected and sun-dried. Improve germination technology, prevent seed damage, improve seed vitality and disease resistance.
3. Sowing at the right time, the seeding density should not be too large. Seeding should be carried out when the temperature is stable at 6 °C. Do not blindly prematurely. In theory, the seeding density is preferably 300 g/m2. However, in actual production, farmers often increase the amount of sowing in order to save production costs such as agricultural film, and take into account the rate of emergence and use of rice transplanters. Even so, the seeding rate must not exceed 500 g/m.
4. Seedbed management. It is necessary to do a good job in cold prevention, heat preservation, ventilation, and training of seedlings to improve the disease resistance of seedlings and prevent and alleviate the occurrence of blight and disease.
5. Strengthen field management. It is necessary to do a good job in cold prevention, heat preservation, ventilation, and refining, to ensure the front protection (pre-emergence insulation), central control (temperature control after emergence to 3 leaf stage), and post-refining (temperature adjustment from 3 leaf stage to transplanting), advocate Dilute early seedlings, control temperature and humidity are not long.
One leaf and one heart period should maintain water temperature as low as 25~30~C. After the second leaf stage, it must be gradually adapted to cold conditions. The temperature of the three-leaf one heart period should not exceed 25 °C, and the soil moisture is sufficient, but it should not be too wet. After the 3 leaf stage, the film should be exposed to ventilation during the day. If there is no frost at night, it is best to expose the film to low temperature, so that it can cultivate strong cold resistance.
6. The seedbed soil disinfection is sprayed with 3.2 times of water for 300 times of water, and soaked with Guanghuling water for 24-48 h or 500-1000 times for 1 leaf 1 heart. Rice seedlings 1 leaf 1 heart period, each plate is sprayed with 15% Lishenling solution 0.9 g plus water 1 L. Spray with 70% dikesone powder 500 times solution or 1% ammonium sulfate, and pay attention to keep the soil moisture to prevent the damage of the blight. In the early stage of the onset of seedlings, Shi Liqing clears 1 to 1.5 g per square meter of medicine, and evenly sprays water on the seedbed.
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