Whitefly belongs to the family Homoptera Aleyrodidae, a small insect that feeds on plant juices with a sucker. At present, the whitefly pests with serious damage on vegetables are mainly Bemisia tabaci and Trialeurodes vaporariorum, which poses a serious threat to vegetable production in China. Among them, B. tabaci is currently the only species known as "Super bug" in countries around the world.
1 Hazard situation
Greenhouse whitefly was seriously threatened by the production of greenhouse vegetables in the north of China during the 1980s and 1990s. With the invasion of China in the 1990s and the beginning of this century, B-type B. tabaci and Q-type B. tabaci have invaded China, and in the south and north, the shed greenhouse vegetable production base has been in a state of serious damage. Many provinces have exploded. According to reports, in China's North China and South China, there are more than 300 host plants, which mainly harm watermelon, eggplant, tomato, cowpea, zucchini, cucumber and other vegetable crops.
The nymphs and adults of the whitefly can harm the plants, and suck the plant juice through the sucking mouth device, which affects the growth and development of the plants. The honeydew secreted by it is easy to breed other pathogenic bacteria, causing the occurrence of coal pollution, affecting the photosynthesis and fruit quality of the plants. More importantly, whitefly pests such as Bemisia tabaci are important media for many viral diseases, with more than 110 types of poisoning.
2 Causes of difficulty in controlling powder meal
2.1 shed production environment
Temperature has a great influence on the growth and development of whitefly population. It is prone to outbreak under dry heat conditions, and the suitable temperature range is 23 to 32 ° C, and the ability to withstand high temperature and low temperature is strong. The temperature of most greenhouse greenhouses is generally controlled at 25 ~ 30 ° C, which is suitable for the growth and development of Bemisia tabaci, which is conducive to its growth and reproduction. The close connection between the facilities in various regions and the production of open field vegetables is intertwined and mature, which facilitates the occurrence of whitefly. In winter, the winter is mainly on the facilities and vegetables. After the temperature rises in the spring, as the vegetables in the facility are released, the migration will spread to the open field, so the whitefly can be an annual hazard.
2.2 Hazard characteristics of whitefly
The development of locusts, nymphs, and adult worms can occur in the tropical and subtropical regions for 11 to 15 generations a year, with overlapping generations. Under suitable conditions of temperature and humidity, such as at 25 ° C, it takes 18 to 30 days to develop from egg to adult, and the amount of eggs laid is large. Both nymphs and adults can damage the plants, and they are distributed on the back of the leaves. Strong. In addition, the host family of Bemisia tabaci has a wide range and can be moved on different vegetables, which brings difficulties to the control of whitefly.
2.3 increased resistance to whitefly
Due to the large amount of B. tabaci, the damage is serious, and the excessive use of chemical pesticides prevents the drug resistance from increasing rapidly. At the same time, due to the irrational use of drugs for a long time, it has caused damage to the natural enemies of B. tabaci, breaking the ecological balance and preventing natural enemies from effectively controlling.
3 Comprehensive control measures
3.1 high temperature shack
During the summer off-season period, high temperature suffocation can effectively eliminate the whitefly in the shed.
3.2 Strengthening cultivation management
Add fully decomposed organic fertilizer, cultivate robust plants, enhance the resistance to pests and the ability to recover after damage; timely clean up the residual branches and leaves in the shed before planting, bury or burn them deeply, and pay attention to clear the surrounding weeds. Reduce the number of whitefly host to reduce the population of whitefly population; try to avoid continuous cropping or intercropping with solanaceous vegetables, and should be rotated with celery, amaranth, etc. to reduce the population of whitefly.
3.3 Physical control
(1) The yellow plate is used to make the yellow color have strong characteristics. After the planting, the yellow plate can be used to monitor and control the whitefly. At the same time, it can also prevent important pests such as spotted fly and aphids. The plate is equal to the upper leaves of the plant, and it is preferable to place 25 to 30 pieces per 667 square meters.
(2) Insect net isolation The insect net is installed in the upper and lower vents and the doorway of the shed, which is more than 40~60 mesh.
(3) Natural enemy control can choose to release natural enemies in advance, such as parasitic natural enemies, larvae, predatory natural enemies, grasshoppers, etc. to control the population of whiteflies.
4 Chemical control
(1) Pre-treatment of seedlings can be prevented by planting 10% imidacloprid WP 2,000 times solution or after planting, using 25% thiamethoxam water dispersing granules 7,500 times solution to prevent rooting.
(2) Cultivation of smog method in shed room, using 15% dichlorvos agent 300-400 g per acre (667 square meters), or 20% isopropyl smoke agent 200-300 g smoked smoke control, ignited in the evening, closed Smoked for 8 to 12 hours.
(3) Spraying method for prevention and control in the early stage of whitefly, 10% imidacloprid wettable powder 2,000 times solution, 50% clothianidin water dispersible granule 9,000 times liquid, or 10% nitenpyram water 1000~2,000 Double liquid, or 24% spirotetraethyl ester suspension agent 1,500 ~ 2,000 times liquid spray control, pay attention to the even and negative surface of the leaves should be evenly used, so that timely medication, rotation medication.
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