First, the damage situation
Whitefly is mainly responsible for cucumbers, zucchini, pumpkins, melons, tomatoes, peppers, eggplants, jack beans, cowpeas, peas and wild vegetables such as dandelions. Many weeds such as Daxue and Tian Xuanhua are also hosts of whitefly.
Whitefly on the host plant caused damage: 1 adults and nymphs suck host plant sap, the victim plant leaves chlorosis chlorosis, wilting or even dead, leading to reduced greenhouse vegetable production or out of production. 2 Secretion of honeydew on host plants, causing coal pollution, greatly reducing the value of vegetable products. 3 spread viral disease.
The occurrence of this insect is related to the crops grown. The population density is very high on cucumbers and kidney beans, but it is difficult to develop populations on rapeseed, spinach and leeks.
Because of its strong reproduction, the breeding speed is fast, the population is large, and the body is small and easy to hide, making it difficult to control.
Second, the law of occurrence
Whitefly may occur in more than 10 generations within a year under greenhouse conditions. The phenomenon of overlapping generations is obvious, and it cannot survive outdoors in winter. The optimum temperature for whitefly breeding is 18°C--21°C. It takes about 30 days to complete one generation under greenhouse conditions. One day to three days after emergence of adult mate can lay eggs, and parthenogenesis can also be performed. All females. The population of whitefly has gradually grown from spring to autumn to its peak.
1. Adults. Small body, pale yellow, female body length 1 mm - 2 mm, wingspan 2 mm - 2.3 mm; male body length 0.8 mm - 1 mm, wingspan 1.7 mm - 2 Mm. Wing membrane covered white wax powder. With tenderness, the adults always lay eggs on the top leaves as the plants grow until the host plants are topping.
2. egg. It is 0.22 mm to 0.26 mm in length, 0.06 mm to 0.09 mm in widest point, and the egg has a shank and the shank length is 0.03 mm. It is light yellow at the time of first production, and then it is gradually purple-black. The egg laid by the egg stem is inserted into the leaf tissue from the stomata and maintains the water balance with the host plant. It is not easy to fall off.
3. Nymphs. It is oval, flat, 0.52 mm long, with dozens of different lengths of wax punctures on the body edge and back, and two tails long. Within 3 days after hatching, the back of the leaves can be used for a short distance walk. When the mouthparts are inserted into the leaf tissue, they lose the function of crawling and start to fix on the back of the leaves to damage the crop.
4. pupa. Oval, milky white or light yellow, opaque, body length 0.7 mm - 0.8 mm, body thickness 0.18 mm, body back with 5 pairs of wax - -8 pairs, body back with 10 pairs of wax wings.
The open spring insects originate from the greenhouse and can be controlled by the ventilation of the greenhouse or the transplanting of the seedlings to the open field and migration to the open air.
Third, human factors play an important role in the spread of prevention and control methods. Whiteflies are spread in greenhouses in the spring and early summer and spread to open field vegetables, and return to the greenhouse in the fall and early winter. In order to cut off the natural life history of the two important links that they move in and out of the wormland, they can produce long-term
The prevention and control of greenhouse whitefly should implement the principle of “prevention first, comprehensive prevention and controlâ€, adopting agricultural control as the basis, rational use of pesticides, combined with comprehensive prevention and control technology of biological control and physical prevention and control to reduce the amount of pesticides and enhance the control effect.
1. Agricultural measures prevention. In the 1st occurrence area, we encourage the cultivation of celery, leeks, glutinous yellow, rapeseed, and other vegetables that are resistant to low temperature while whitefly does not like to eat, and appropriately reduce the cultivation of cucumbers and tomatoes; 2 cultivating “insect-free seedlings†(also known as “clean seedlingsâ€). ) Separate the nursery bed from the production greenhouse, remove the weeds and stubbles before the nursery, thoroughly smoke the remaining insects, hang the insect nets in the greenhouse vents, and control the foreign insects; 3 greenhouses; avoid cucumbers and tomatoes near the greenhouse Severe vegetables such as eggplants, eggplants, beans and other whiteflies are used to promote the cultivation of cruciferous vegetables that do not like to eat whitefly; 4 to avoid mixing cucumbers, tomatoes, and beans, so as not to provide environmental conditions for the occurrence of whitefly.
2. Physical control. Whitefly has strong yellowing potential and can be trapped and killed by yellow plates in greenhouses. Use fibreboard or cardboard to cut into strips of 1 mx 0.2 m, painted orange-yellow, and coated with 1 layer of viscous oil. Placed between the rows of plants and plant height. Density of 30 pieces/mu -40 Blocks/Mu, apply 1 coat of viscous oil for 7 days to 10 days. Yellow prawns can also be used. The seedling stage and colonization period can be used to control the initial number of pests and protect natural enemies. This method is easy to operate, economical and practical, free from pollution, and can be used in conjunction with other measures to produce good control results.
3. Chemical control. Due to the overlap of whiteflies generations, there are various forms of insects on the same crop and must be used several times in succession to obtain better results. Spraying should be carried out in the early stage of the occurrence of whitefly. The use of pharmaceuticals is: 125% buprofloates EC 1000 times - 2000 times, the concentration can be properly grasped according to population density. When the amount of insects is too large, 1000 times of liquid can be used to add a small amount of pyrethroid pesticides, and spraying once -2 times can effectively control the whitefly. Bufalin has special effects on eggs and nymphs, but it is basically ineffective against adults. 22.5% Uranus EC 3000 times can kill adults, nymphs and cockroaches, but the killing effect on eggs is not obvious. Mixing Puerarin with Uranus can receive a comprehensive killing effect. 3 Use 30% Dagong Chen WP 2g (active ingredient)/mu, and the effective period can reach 30 days. 425% extinction of manganese emulsion (also known as methyl killing) 1000 times, effective for adults, eggs, nymphs. 52.5% kungfu emulsifiable concentrate 3000 times or 20% extinction emulsifiable concentrate 2000 times continuous use, the effect is better. 6Sprinkle dichlorvos with sawdust, wheatgrass or straw, etc., and add a piece of red-hot coal balls to smoke. 80% of dichlorvos per acre or 0.4 kg of 0.5 kg of dichlorvos should be taken into account when using pesticides. Prevent whitefly from producing drug resistance.
4. Biological control. 1 In the initial stage of the occurrence of whiteflies, the larva was released for biological control. When the adult density of whitefly was 0.5 head/strain or less, the release of 15 larvae and bees into the bee could effectively control the damage of whitefly. Once every two weeks, a total of three times. 2 Manually release grasshoppers. In the first 3 to 4 months of the occurrence of whitefly, 10 grasshoppers/m2 were released.
5. Low temperature extermination. Using late autumn, deep winter, early spring, the first time to clear the shed debris inside the shed, uncover the plastic sheet, use the low temperature freezing for 3 days, and freeze the adult and nymphs. The vents in the sheds are to be screened with insects.
6. Covered silver film. Five kilograms per acre with silver-gray film, and cover the same film, can also use 1.5 kg of silver gray film, the film cut into 10 cm -15 cm wide strips, pulled into a mesh-like, can drive whitefly.
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