Major biological hazards of crops refer to biological disasters that occur in large geographical areas and cause serious losses to crop production. Including sudden pests and epidemic diseases: grasshoppers, armyworms, aphids, rice stem borer, rice blast, potato late blight, etc.: large-scale serious occurrence of common biological disasters are corn borer, soybean meal, soybean red Spiders, soybean heartworm, soybean sclerotinia, farmland rodents, grass damage and physiological diseases and phytotoxicity, new and phytosanitary pests and diseases, and other sudden, recurrent and crops may cause A major hazard to a biological disaster.
China is a country with frequent, frequent and recurring crop diseases and insect pests. Since ancient times, pests and diseases, floods and droughts have been called China's three major natural disasters. There are more than 1,400 species of crop biological disasters, of which the most serious diseases are wheat rust, powdery mildew, scab, etc. The diseases that damage rice are rice blast, bacterial blight, sheath blight, etc. There are big spot disease, small spot disease, etc., and there are blight and yellow blight in cotton. The main pests include wheat midge, aphids, armyworms, rice planthoppers, rice aphids, corn borers, cotton bollworms, soybean borers, and underground pests. In China, the total area affected by agricultural biological disasters is 236 million hm2 per year. Each crop often suffers from 3 to 4 pests at the same time, losing 10 million tons of grain, 400,000 tons of lost cotton, and seriously reducing fruits, vegetables and oil. And the yield and quality of other cash crops, at present, the loss of crop pests and diseases in China is no less than a major flood loss.
In recent years, due to various factors such as global warming, changes in farming and cultivation systems, and frequent international agricultural trade, the frequency of crop pests and diseases in China has increased year by year, and the losses have increased year by year. Crop diseases are more concentrated in the east than in the west. From north to south, the northeast is mainly corn-sized spot disease, North China is mainly wheat stripe rust, the Yangtze River basin is mainly wheat scab, and South China is mainly rice blast. The main pests from north to south are the sticky insects in the northeast and north China, the aphids on the Yellow River beach and along the beach, the Yangtze River basin and the south of the rice blast, showing the distribution with temperature gradient.
The rice diseases in China are mainly distributed in the south of the Qinling-Huaihe River, which is the main distribution area of the three major diseases of rice production in China (rice blast, sheath blight and bacterial blight).
At present, more than 100 countries in the world have issued laws and regulations on the prevention and control of crop diseases and insect pests, such as Japan, India and other countries in 1950 and 1985 respectively, the United States in 1990, Indonesia, Bangladesh, Vietnam, Kazakhstan, Mongolia, Nepal, South Korea and other countries have also issued corresponding regulations on the prevention and control of crop diseases and insect pests laws and regulations. But our country has not promulgated the relevant laws. Due to the lack of corresponding laws and regulations, the responsibility of prevention and control work is unclear, the system is incomplete, the safeguard measures are difficult to be in place, and the disaster prevention work is often in a passive situation.
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