Corn rough dwarf

In the sixties and seventies, the disease was severely occurred in parts of our country. In recent years, the northern provinces of Fujian, Shandong, Shaanxi, Shanxi, Liaoning, and Tianjin have experienced outbreaks. In 1997, more than 2.33 million hm2 occurred in the country, which seriously threatened the development of corn production. The reason: First, corn varieties are not resistant to disease. The second is the interplanting of maize and wheat or planting with cotton, vegetables, etc., and the shrinkage disease extends to cotton fields and corn fields in vegetable areas. The third is that the period of the susceptible period of maize is coincident with the age of the planthopper. It is an important reason that the current maize planting system is conducive to the epidemic of the disease. Fourth, the warm and dry winter, with little rain in the spring became the favorable climatic conditions for the epidemic.

Symptoms of corn rough dwarf disease are severely dwarfed, only l/2-1/3 of the height of the healthy plant, dark green leaves, broad hard, short and hardy, showing an opposite shape, waxy white protrusions on the veins on the back of the leaves. Roughness is obvious. Sometimes there are waxy white streaks on leaf sheaths, ears and leaves. Diseased plants were divided into many parts and the roots were undeveloped and easy to pull out. Although the light is drawn, but half wrapped in the bell mouth, tassel abortion or dysplasia, underdeveloped filaments, less fruitful, seriously ill plants more premature death or no harvest. In addition to harming corn and sweet corn, the disease can also harm the symptoms of barley, wheat, oats, sorghum and millet.

The pathogen Maize rough dwarf virus is abbreviated as MRDV. It is called corn rough-cut virus and belongs to virus. The virion is spherical and has a size of 60-70 nm and is present in the raised part of the cells of susceptible plants. Passivation temperature of 80 °C, 20 °C can survive for 37 days.

Transmission pathways and disease conditions rely mainly on the transmission of Delphacodes striatella. Adults and nymphs of Laodelphax striatellus were overwintering in weeds in the fields and moved into corn fields in late spring. In addition winter wheat is also one of the virus wintering sites. Poisonous spurts in spring spread the virus to turn green wheat and then spread it to corn. The corn was susceptible to disease before the 5th leaf stage, and the resistance at the l0 leaf stage was enhanced. The occurrence of the disease is related to the number of poisonous planthoppers and the cultivation conditions. The emergence of corn to the fifth leaf stage is likely to occur when the insects encounter the peak of the insect transfer. Sets of farms, early sowing fields, and weedy corn fields suffer more. The incubation period is 10-20 days. In addition, it has been reported that insecticides in Yunnan Lijiang region are whitebacked planthoppers. Maize seedling stage is a sensitive period of corn rough dwarf disease. Large, wheat, and grass weeds look like Acacia and Setaria are the main hosts for the wintering of the crude virus. The crude virus can proliferate and overwinter in the body of Laodelphax striatellus, but it cannot be passed from egg to egg to the next generation. Laodelphax striatellus mainly thrives in wheat fields, green manure fields, and weeds in the rhizosphere, and in spring, on large plants, wheat, and weeds, and then partially transfers to rice to reproduce and cannot reproduce on corn. The winter and spring climate is warm and dry, and it is favorable for the occurrence of the planthopper in summer. Currently promoted corn varieties and their inbred lines, generally do not show resistance to rough dwarf disease, many susceptible varieties, such as Zhengdan 2, Bodan 1, group 105, inch night l07 disease severity. There is a general increase in the proportion of interplanting and interplanting corn, coupled with a large amount of toxic sources, and the possibility of the growth of rough dwarf disease.

Prevention methods (1) Strengthen monitoring and forecasting and guide field control. (2) Selection of resistant varieties such as Qun Zhuang 101, Jing Huang 113, Yu Nong 704, 2569 Winning, Xidan No. 7, Zhong Dan No. 2, Zhong Dan No. 4, Nong Dan No. 5, and Zheng Dan No. 4 etc. . (2) Advocate contiguous planting to avoid large-scale cultivation of single disease-resistant varieties, so that the sowing date is basically the same. Avoid the planting of the flower arrangement and a small part of the corn field's disease-affecting growth period and the coincidence of the occurrence of the planthopper, causing the poisoning of Laodelphax striatellus. (3) Before corn planting or before emergence, large areas will be cleared of weeds in fields and fields to reduce the source of poisons and promote chemical weeding. (4) Reasonable fertilization, irrigation, strengthening of field management, shortening the time of corn seedlings, reducing the chance of transmission of poisons, and improving the resistance to disease of corn. (5) Carbofuran or other seed coating agent or 2% HA. Maize seed dressing and 20% virus A, respectively, according to the seed amount of 0.2% corn seed coating or dressing, can effectively control seedling stage planthoppers, reduce the spread of viral diseases. (6) Spray 40% omethoate EC 1500 times and 50% methamidophos EC 1500 times before and after corn sowing and at the seedling stage. (7) Corn seedling spraying 5% bactericidal liquid WP 500 times or antiviral (300% mushroom proteoglycan water antiviral agent No. 1) 300 times, 15% virus will be wettable Powder 500-700 times liquid. (8) It can also be used in the period of poisoning caused by Laodelphax striatellus, especially before the 7-leaf stage of corn, spraying 2.5% of fluocinol emulsifiable concentrate 1000 times liquid and 10% Virus WP 600 times, spraying every 667m2 A good liquid 30-40kg, every 6-7 days, even spray 2-3 times, can be more effective.

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