Control techniques of Rice Vertical Blight

Rice vertical blight is one of the most important diseases of dry-raised rice seedlings. The main causes of the disease are low temperature, excessive temperature difference, alkaline soil, insufficient light, weak seedlings, too large seed quantity and so on. The main symptoms in the field are seedling withering after emergence, easy to pull out, rot at the base of the stem, smell of rotten pear, death of the whole disease, and red mildew at the base of the diseased plant.

The onset period of rice blight

At 2-3 leaf stage, the endosperm was nearly exhausted, and the cold resistance was the worst. When the daily average temperature was lower than 12-15 C, the growth was blocked, the disease resistance was significantly weakened, and the pathogen was easy to invade. At this time, the disease blight was most likely to occur in case of low temperature, overcast and rain. Therefore, the 2-3-leaf stage of dry-raised seedlings is the main epidemic period of blight.

Harmful symptoms of rice blight

The main results are as follows: 1. Bud rot occurs before emergence or just when it is unearthed. The young buds or roots of the seedlings turn brown, and the diseased buds are twisted and rot. There is a mildew layer at the base of the seed or bud.

2. Needle rot mostly occurs from the needle-setting stage to the 2-leaf stage of the seedlings, the heart leaves of the diseased seedlings are withered and yellow, the leaves do not expand, the base turns brown, sometimes there are brown spots on the leaf sheath, and the diseased roots gradually turn yellowish brown. There is a mildew layer at the junction of the seed and the seedling base, the stem base is weak and easy to break, and the seedlings often form clusters, occur and die in pieces in the seedling bed.

3. Yellow wilt and green wilt mostly occur before and after the 2.5 leaf stage of the seedling, the leaf tip of the diseased seedling does not spit water, the leaf color is withered and wilted, and expands rapidly outward in the shape of a hole, the base and root of the seedling are easy to break, and the leaves are locked. When the weather suddenly clears up, the seedlings quickly show green and withered, and the heart leaves and upper leaves "lock". The leaves of the seedlings were green and the whole plant wilted at last. Honda appeared green and withered after transplanting seedlings.

Causes of Rice Vertical Blight

The main results are as follows: 1. Climatic conditions, low temperature, overcast and rain and lack of light are important conditions to induce blight, among which low temperature is the most important. The disease resistance of seedlings decreased under the condition of low temperature, which was beneficial to the occurrence of disease. If the temperature is too low, it has little effect on the development and infection of pathogens, but it is disadvantageous to the growth of seedlings, poor development of roots and decreased ability of absorbing nutrients, which is more conducive to the development of diseases. Such as continuous low temperature or sunny after overcast and rain, insufficient soil moisture, physiological imbalance of seedlings and aggravation of diseases.

2. Infection cycle, rice blight belongs to soil-borne disease. It is caused by a variety of pathogens, including Fusarium oxysporum, Fusarium graminearum, Fusarium oxysporum, Fusarium oxysporum, Fusarium Fu, Rhizoctonia solani and Rhizoctonia sclerotiorum, as well as flagella, Fusarium oxysporum, Fusarium Fusarium oxysporum generally overwinters with hyphae and chlamydospores in the disease remains and soil of many kinds of hosts. When the environmental conditions are suitable, conidia are transmitted by airflow and infected. On the other hand, Rhizoctonia overwintered with hyphae and sclerotia in host disease residues and soil, and spread among seedlings by mycelium spread and infection.

3. Seedling quality, Rhizoctonia and Fusarium wilt pathogens such as Rhizoctonia solani and Fusarium oxysporum widely exist in soil, which are weak parasites and can generally live saprophytic life in water or soil. The pathogenicity of these bacteria is not strong, they are generally not suitable to infect strong seedlings, only when the bad weather and improper management, resulting in weak seedling growth, reduced resistance, a variety of weak parasites can take advantage of the deficiency and spread. Therefore, poor seedling quality, weak growth, poor disease resistance and stress resistance are the direct causes of bacterial blight.

Integrated control of rice blight

The prevention and control of blight should be based on the combination of prevention and control.

1. In the 1-2 leaf stage of rice seedlings, Olik (Qingkulike) 50ml + 15ml of garlic oil was sprayed with 15kg water, once every 7 days, twice in a row. In order to enhance the disease resistance of plants, it is recommended that foliar fertilizer (Wofengsu) 25ml should be added every 15 kg of water during spraying. In the middle and later stages of the disease: use Aolike Qingkulike 100ml + garlic oil 15ml for spray, once every 3 days, 2 to 3 times in a row.

2. Careful selection and drying of seeds. Improve germination technology, prevent seed injury, improve seed vitality and disease resistance.

3. Sowing at the right time, sowing density should not be too high. Sow seeds when the temperature is stable through 6 ℃. Don't rush early blindly. Theoretically, the sowing density should be 300 g/m2. However, in the actual production, in order to save production costs such as agricultural film, as well as considering the emergence rate, the use of rice transplanter and other reasons, farmers often increase the sowing rate, even so, the sowing amount must not exceed 500g.

4. Seedbed management. It is necessary to do a good job in cold prevention, heat preservation, ventilation, and seedling training, improve the disease resistance of seedlings, and prevent and reduce the occurrence of blight and evil seedling diseases.

5. Strengthen the field management. It is necessary to do a good job in cold prevention, heat preservation, ventilation and seedling refining, such as pre-protection (heat preservation before emergence), central control (temperature control from 3-leaf stage to 3-leaf stage), and post-refining (temperature adjustment from 3-leaf stage to transplanting). Sparse planting and early seedling raising are advocated, and temperature and humidity are not overgrown. The temperature of one leaf should be kept at 25: 30C and watered as little as possible. After the second leaf stage, it must be gradually adapted to the cold condition. The temperature in the three-leaf one-core stage should not exceed 25 ℃, and the soil moisture is sufficient, but it should not be too wet. After the third leaf period, the film should be ventilated during the day, and if there is no frost at night, it is best to expose the film to withstand low temperature, so that strong seedlings with strong cold resistance can be cultivated.