Corn stem rot, also known as corn stalk rot, commonly known as corn bacterial wilt. In recent years, due to the frequent introduction of maize inbred lines and hybrid varieties between regions, the original species of inbred lines and some hybrids with poor disease resistance were widely planted between regions, resulting in the disease. The mutual spread between the corn producing areas caused the plants to be withered and the grains were not full, which seriously affected the yield of the original varieties of corn and caused great economic losses to the company and the farmers. The incidence of general interplanting corn and summer sowing maize is up to 10% to 25%, which is as high as 48.6%, resulting in a reduction of production of about 25%. At present, the disease prevention and control measures are still based on disease-resistant varieties, but because of the long breeding cycle of varieties, they often begin to compare disease resistance and become susceptible varieties after 4 to 5 years, which brings about extremes in production. Big difficulty. The law of occurrence of the disease and its comprehensive prevention measures are briefly described as follows:
First, the law of occurrence
1. Symptoms and characteristics: The disease is an invasive disease of the whole plant. From the end of milk ripening period to the wax ripening period, it is the peak period of obvious disease. It generally begins from grout to milk ripening period. The typical symptoms are as follows:
Stem and leaf blue and dry type: When the onset of disease, it gradually expands upward from the lower leaves, showing water-stained and blue-green, and then the whole plant is blue and dry. Some of the diseased plants exhibited acute symptoms, i.e., acute blighting of the whole plant at the end of milk ripening or during the wax ripening period. There was no apparent gradual progress from bottom to top, and this condition was more common in sunny days after rain.
Stem rot type: The roots of the plants are significantly stunted, with short and short roots. The stems of the diseased plants become soft at the base of the stems. The stems are examined and the pith is loose. The roots and the ground are often rotted between 1 and 3 knots. It is easy to infuse, appearing white in the early stage of the disease when it is wet, and pink mold in the later stage.
Ear rot type: Some ears droop after onset, the handle is soft, the leaves are blue and dry, and it is not easy to peel. The sick ears are loosely arranged, easy to thresh, and the grain is gray and dull.
2. Cause of disease: Stem-based rot is a type of disease caused by a variety of pathogenic bacteria alone or combined infection caused by root and stem rot, mainly caused by the infection of Pythium and Fusarium, symptoms expressed on corn plants It's different. The optimum temperature for the growth of Pythium was 23-25°C, and the optimum temperature for the growth of Fusarium was 25-26°C. The requirement for the growth of Pythium in soil was higher than that of Fusarium. Therefore, the isolation frequency of pathogenic bacteria in different ecological areas is different, and the frequency of pathogenic bacteria isolation in the same ecological area has significant differences between years and regions. Rainy areas are often dominated by Pythium-type stem rot, while in dry areas, Fusarium-type stem rot mainly. The disease is a typical soil-borne disease. The pathogen survives overwintering both inside and outside the diseased tissue and in the soil, becoming the main source of infection in the following year. In the field, it can be spread by wind and rain, irrigation water, machinery and insects, and it has repeatedly infested. The longer the duration of continuous cropping, the more pathogenic bacteria accumulated in the soil and the more serious the disease. On the other hand, there is less incidence of bacteria in the oysters. Generally, early-planting and early-maturing varieties are severely affected. This is because the suitable spores of temperature and humidity in the soil are easy to germinate, which is consistent with the suitable growth period of corn, resulting in an increase in the incidence rate. In general, the onset of flat land is lighter, and the onset of land and depression is heavy. The soil is fertile, the organic matter is abundant, the conditions for irrigation and drainage are good, the incidence of strong corn growth is light, and the sandy soil is thin, the drainage condition is poor, and the corn growth is weak and the incidence is heavy. The stem rot of spring corn occurred in mid-August, and the summer corn occurred in the middle and early September. The incidence of intercropping corn in wheat was between the two. The reason for this is generally believed to be heavy rain in the period from corn powdering to early milk-curing, followed by rain after rain, rapid rise in temperature, and more occurrence of blue-green symptoms. The inoculation test showed that the incidence of high-humidity and moderate-humidity in F. graminearum inoculation was 35.71%, and the incidence rate of low humidity was 21.43%. The incidence of moderate humidity and low humidity in F. moniliforme treatment was 14.28%. The incidence rate is 0. Among them, Fusarium graminearum has the strongest pathogenicity. Therefore, soil moisture is the main factor affecting the pathogenicity of pathogens. There was significant difference in resistance to stem rot between varieties, but there was no significant difference in the resistance of the same variety to Pythium and Fusarium, ie, the varieties of Pythium-resistant fungi were also resistant to Fusarium, and vice versa. In general, the flattening of the plant type is more severe than the compact disease, and the height of the plant is heavier than that of the dwarf. From the observation of the resistance of summer corn and spring corn in Hexi Corridor, summer corn has stronger disease resistance than spring corn, such as Zhongyu No. 5, Gyeonggi No. 109, Gyeonggi No. 108 and Kezao No. 3, etc. 3527, Nongda 3138, and Gaoyou 115 have low incidence, low disease index, and strong disease resistance.
Second, comprehensive prevention and control measures
1. Breeding and cultivation of disease-resistant and disease-resistant varieties: Inbred lines that have been selected in recent years have been obtained by Bai, Ji 815, 870, 337, Va35, Pi 524, Bao 102, Shen 219, Cheng 191 and Jing Department 01 and so on. There are Zhongdan 11ã€Shandan 9ã€Shendan 7ã€Qidan 4ã€13ã€Nong 60ã€Jidan 141ã€122ã€118ã€Tangyu 1 and Jintang 1 among the hybrid and hybrid combinations. . Should be selected according to local conditions.
2. Remove the residue of field diseased plants: Remove the diseased male and female plants in time when the male corn is grown. After the corn was harvested, the diseased plants were completely removed and burned centrally or in combination with deep-turning land.
3. Crop rotation: The rotation of maize and other non-host crops was implemented to prevent the accumulation of soil pathogens. Onset of heavy land can be carried out for 2 to 3 years with rice, potato and vegetable crops.
4. Appropriate late sowing: North Spring Maize, sowing from late April to early May, can prevent the occurrence of stem rot, which is 11.3% to 67.5% lower than that of early sowing and 12.6% to 32.3% increase in yield. Interplanting corn was sown from late May to early June. Summer corn planting disease around June 15 is mild.
5. Rational fertilization: Based on the application of basal fertilization, additional potassium fertilizer or phosphorus and nitrogen fertilizers should be used in jointing stage or booting stage of corn. Potassium-deficient plots are generally treated with potassium sulfate 100-150kg/ha; potassium-deficient blocks are generally applied with potassium sulfate 70-105kg/ha. When corn is sown and pumped, zinc sulfate, urea, and ternary compound fertilizer are applied to the soil at a rate of 22.5 to 30.0 kg, 225 kg, and 225 kg per hectare, which can increase production by 8.4% to 10.2%.
6. Biological control: The use of increasing production of bacteria at a seed weight of 0.2% for seed dressing has a certain control effect on stem rot. A 110E6 spore suspension of Trichoderma harzianum or Trichoderma viride was inoculated per gram of air-dried soil to significantly inhibit the germination of Fusarium graminearum spores, or inoculated with soil in soil and added 4-6 per gram of soil. The micro-triazolinone control effect is more significant than that used alone. At the same time, before the seed coating, the use of corn seed dressing (ZSB) 1: 40 seed dressing, or soaking seedlings, or root protection seed coating agents have a certain inhibitory effect on corn stem rot. The control effect is obvious.
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