Sheath blight is a common disease in rice cultivation, and its damage is great. Once the prevention and treatment is not timely, the rice will dry up and die, affecting rice yield. What is the cause of rice sheath blight? The following are detailed causes and control measures for rice sheath blight. I hope to help the growers.

1 Causes of rice sheath blight

The pathogen of rice sheath blight is mainly Rhizoctonia solani, which is observed under normal conditions. The hyphae are colorless at the beginning, and the pale brown sclerotia appears when mature. The actual phytotoxicity of the bacterium sclerotia is strong and can survive in all kinds of harsh environments. It is the primary inducing pathogen for the large-scale transmission of rice sheath blight. In addition, excessive planting density of rice, improper management of water and fertilizer, and unreasonable drug control measures can lead to the occurrence of sheath blight and affect the control effect.

2 Characteristics of rice sheath blight

Rice sheath blight is a disease caused by high temperature and high humidity conditions. When the field temperature in the rice growing area is rising (about 20 ° C, humidity is 80%), the sheath blight begins to gradually occur and spread. When the field temperature in the planting area is greater than 25 °C and the relative humidity is greater than 90%, the disease propagation speed will continue to increase. The rice planting field has long-term water accumulation and high humidity, which provides basic conditions for the occurrence and spread of sheath blight. If excessive nitrogen fertilizer is added during the fertilization management process, the seedlings will be blocked in advance to promote the occurrence of sheath blight. In the case of normal planting, the actual disease resistance and morbidity of different varieties are different, the incidence of high stalk rice varieties is low, and the incidence of dwarf rice is heavier.

3 Basic symptoms of rice sheath blight

Sheath blight has different degrees of damage to rice sheath, leaves, ears and stems. The initial stage is mainly in the leaves and sheaths where the plants are close to the water surface. During the initial infection of rice, most of the diseased parts showed dark green water-immersed and fuzzy spots. After the lesions spread further, they gradually formed a cloud pattern. Gray-green or taupe will appear in the middle of the lesion, and the edge will appear dark brown after the rice tissue is destroyed. When the disease occurs more seriously, a larger number of lesions will produce larger lesions after the intersection of the smaller lesions, causing the leaves to begin to yellow and then gradually die. The damage of the stem position is similar to that of the leaves. When the ear is infested, it will initially appear dark green. As the invasive time prolongs, it will appear taupe, and the rice cannot be headed normally. In the high-temperature, high-humidity growth environment, the sclerotia appears in the affected part of the sheath blight, and the sclerotium is darker in color and easy to fall off.

4 The incidence of rice sheath blight

Rice sheath blight is a fungal disease. The sclerotia of the pathogens overwinter in the environment of planting soil, grass stalks, weeds, etc., which is the initial source of infection. When cultivating in the spring, most of the sclerotia that successfully survives winter will float on the water and then attach to the rice plants. When the natural environment temperature is more suitable, the sclerotia will continue to germinate, forming hyphae, infecting rice, causing rice to develop, and under high temperature and high humidity conditions, it can lead to the outbreak of rice sheath blight. After rice planting, the disease occurs prematurely, too much, and too heavy, which is a common phenomenon in the current rice area.

5 Comprehensive control measures for rice sheath blight

5.1 Selection of varieties with better disease resistance

Rice cultivation is mainly based on the selection of rice varieties, because good varieties can block pathogenic bacteria and reduce the probability of disease occurrence. According to practical research, the waxy protective layer of japonica rice plants is thicker and has more silicified materials, and the actual disease resistance is better. Indica rice is the second, and the actual disease resistance of japonica rice is the worst. In the same planting environment, the early diseased varieties have lower disease resistance, and the late-maturing varieties have better disease resistance.

5.2 Timely removal of the source

Before transplanting rice, it is necessary to promptly remove the sclerotia floating on the surface of the rice field, and reduce the number of bacteria. The actual operation is as follows: by raising the water level (water level height 3.3-6.6 cm), the sclerotia floats on the water surface and stays for a period of time, so that the dry branches, weeds, sclerotia, etc. floating above the water surface After the slag floats in the wind to the corner of the wind and the edge of the field, it can remove the dead branches and weeds and sclerotia floating on the water surface through the sand and other related tools, and then burn it, so that the number of the bacteria source can be effectively controlled. Early and late onset, severity of the disease, effective regulation.

5.3 Water and fertilizer management measures

The principle of fertilization in rice field, fertilization is based on base fertilizer, and can be topdressed in time according to the growth pattern of rice and the actual growth situation. The base fertilizer is mainly based on farmyard manure, and the fertilizer is appropriately supplemented according to the soil fertility. The principle is to control the nitrogen fertilizer and increase the application of phosphorus and potassium fertilizer. Topdressing should be based on the application of tillering fertilizer. It should be carried out 7 to 10 days after the seedlings are returned to the green, and should not be late. The amount of fertilizer applied is about 20% of the fertilization level.

5.4 Adopt other reasonable cultivation management measures

Cultivating strong, reasonable and dense planting, and inserting basic seedlings are important supporting technologies for achieving disease resistance, high yield and high quality of rice, and also an effective measure for comprehensive prevention and control of sheath blight.

At the same time, the growers should apply sufficient base fertilizer, rational topdressing, increase application of phosphorus and potassium fertilizer, and not apply nitrogen fertilizer, which can promote rice growth, increase yield, and improve rice's resistance to disease and disease.

5.5 Chemical control measures

Rice sheath blight in the early stage of the disease, the disease development is relatively slow, the disease develops rapidly in the late stage of the disease, in order to control the disease must be timely drug application. In the tillering period, when the disease plex rate is found to reach 5% to 10%, medication control can be started. The condition of the big baby at the booting stage and the heading stage is developing rapidly. It is necessary to strengthen the prevention and control and control the development of the disease. The conventional medicine can be used with a spray of pesticides such as Jinggangmycin powder, benzomethoxazole emulsifiable concentrate and oxazolol suspension. The medicine must be used twice in a row, and the second medicine is applied about 7 days after the first application, so that a good control effect can be obtained. In addition, pay more water when applying the medicine, and the syrup can have enough liquid to spray into the middle and lower parts of the plant to improve the control effect.

Rice sheath blight is caused by Rhizoctonia solani, and the disease spreads rapidly when the disease occurs. If the control is not timely, it will harm the whole paddy field. Therefore, the seed households must cause planting when planting. The causes of the disease and the prevention and treatment measures can be used by all growers .

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