First, the onion thrips, also known as small white insects, smoke thrips. Adults and nymphs use sucking mouthparts to suck the leaf sap, making the onion leaves form a number of fine long-yellow-white spots. In severe cases, leaves yellow and white, twisted, dead, drooping, seriously affecting the yield and quality of green onions. 1, the law of occurrence. Onion thrips can occur throughout the year, occurring 3-10 generations a year. Adults or nymphs (mostly adults) are allowed to overwinter in leaf sheaths of green onions and in earth seams and deciduous leaves, or in weeds covered with weeds and grass and dung. The suitable environment for harm on the onion is: temperature 23-28°C, relative humidity 40-70%. More than 38 °C nymphs have died one after another, and the hazards have been reduced under conditions of high temperature and high humidity. Onion thrips generally begin to breed in the spring and endanger. In late May to early June, the most serious damage occurred. After July, more rainfall and less harm. Onion thrips adults are afraid of the light, mainly at night, in the backlight during the day generally harm. 2. Prevention and control measures (1) Clear the overwintering sites of onion thrips and reduce overwintering. When planting the land before planting, the stubble and dead leaves of field weeds and former crops should be promptly removed, and buried or burned in a concentrated manner to reduce overwintering sites for onion thrips. Weeding, cultivating, and reducing onion thrips inhabitation and breeding sites during growth of onion. (2) Change the environmental conditions in the field and suppress the occurrence of pests. In the early spring drought, timely irrigation, with a small water pouring method, increase the humidity in the field, inhibit the harm of onion thrips. (3) Entrap adult worms and reduce the population density. Use a white oil board to trap the onion thrips. The method is: use white cardboard, put a plastic film bag, and apply the oil on both sides (add a little zincphos-phine to the oil), and make the prepared white plate at a height of 50 cm from the ground, and determine the position at a distance of 7 meters. In the sunny morning of 9-12 o'clock, the white plate is fixed in the southwest direction. Has a good trapping effect. (4) Chemical control. Available 50% Dimethoate Emulsion, 50% Malathion, 50% Bataan WP 1000 times, 25% chloramphenicol emulsion 6000 times rotation, alternate spraying. Each pesticide is only sprayed once in one growing season of Welsh onion. And stop the medication 10-15 days before the receipt. In order to reduce the amount of pesticide residues in Welsh onion products, the product quality will be up to standard. Second, Liriomyza sativae, also known as leafminer, leafhopper. The larvae travel through the leaves in a zigzagging manner and feed on the leaves. The tortuous meandering tunnel can be seen on the leaves. After the leaves are fed, only two layers of white transparent leaf epidermis are left. In severe cases, one leaf is harmed by multiple insects. Leaf meat is heavily fed, seriously affecting photosynthesis. 1, the law of occurrence. Occurrence of 3-5 generations in one year, wintering in the leaves of the onion and in the soil. In early May, the adult is in its peak period. In the evening, the adults spawn the eggs in the leaf tissue of onion, and the eggs are white. After 4-5 days, the larvae hatch, which means they begin to feed in the leaves. In June, they were the endangered period. The mature larvae phlegm at one end of the tunnel, and after larvae break, the epidermis of the broken leaves begins to emerge. Because the leaf larvae of Onion leaf miner has been harmed in the leaves, the air humidity has little effect on its growth and development, but the influence of temperature is greater, and the weather is hot and the development is unfavorable. 2, prevention and control measures (1) clean the pastoral, eliminating the source of insects. Before and after planting, all residues of leaves and dead leaves must be removed in a timely manner, brought out of the field to be burned and buried deeply, and deeply turned and winterized to eliminate the source of overwintering insects. (2) Trapping adult worms. Use 100 grams of brown sugar and vinegar, add 1000 grams of water to boil, add 40 grams of trichlorfon, adjust to evenness, and mix evenly on 40 kilograms of hay and leaves, and throw it into the field to seduce adult insects. (3) Chemical control. It is important to kill the adults and eggs during the period when the adults are spawning or during the initial period of larval hatching. Spray insecticides and ovicicides once a week starting in early May. Tobacco lime water can also be used to kill eggs, the production method: 0.5 kg of tobacco leaves, soaked in 20 kg of water for a day and night, and then filter out the tobacco leaves and cigarette residues; then use 10 kg of water to turn 0.25 kg of calcined lime milk, and then filtered Mix the tobacco leaf water and lime milk before use and use it. In the adult stage, 40% Dimethoate EC 1000-1500 times, 50% Trichlorfon 800 times, and 25% chlorinated EC 6,000 times were alternately used for alternate spraying. Each pesticide is only sprayed once in one growing season of Welsh onion. And stop the medication 10-15 days before the receipt. Third, the onion to plant flies 1, the law. Three generations occurred in one year and the wintering of pupa or larvae occurred. The first generation larvae were in the mid-May period, the second generation larvae were in the middle of June, and the third-generation larvae were in the mid-October. Adults are most active at noon and concentrate on onions and garlic. The egg period is generally 6 days, and the larval period is generally 17-20 days. The mature larvae spend the winter in the soil. 2, prevention and control technology (1) fertilization drive. Onion flies are rot-feeding, and farm manures such as various manures and cake fertilizers applied to the field must be fully cooked to reduce the accumulation of pests. Many applied to the river mud, clay soil and old house soil as the base fertilizer, river mud, clay soil and old house soil and other odors that the onion flies do not like, and have drunkenness. (2) Elimination of overwintering larvae and cockroaches. The plots of cultivated early spring onions were poked in late autumn, and deep-turned in the late autumn to kill some overwintering larvae and earthworms. In addition, winter irrigation can also effectively kill some of the overwintering earthworms. (3) Adults were killed by sweet and sour liquid. Use 0.5 kg of brown sugar, 0.25 kg of vinegar, 0.05 kg of wine, 0.5 kg of clear water, add a little amount of trichlorfon, pour the prepared sweet and sour liquid into the pot, keep it 5 cm deep, and put it into the field. (4) Chemical control. At the age of adulthood, spray 21% of chlorpyrifos-containing emulsifiable concentrate 3000-4000 times at noon; 2.5% of deltamethrin emulsifiable concentrate 3,000 times; each agent is sprayed once in one growing season of Welsh onion, before harvest Stop medication for 10-15 days. When onion shoots were planted, roots were treated with 75% phoxim 500 times to control larvae damage.
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