First, the symptoms of silver squash and silver squash were damaged. The plant growth was weak, the plant type was short, the leaves were drooping, the leaves at the growing point were shrinking, semi-stagnant, and the internodes at the upper part of the stem shortened; the petiole of stems and young leaves and functional leaves were chlorotic; In the early period, the veins appear white, and the posterior leaves turn white all the time. They glow in the sunlight and look like silver mirrors. They are called the silver leaf reaction, and no abnormalities are found on the leaves. Common whitefly adults or nymphs are common. 3-4 leaves are sensitive. Juvenile melons, melons and flower handles, flower buds turn white, semi-finished melons, commercial melons are also white, or milky white, or white and green, loss of commodity value.
Second, the cause of the silver leaf reaction The zucchini silver leaf reaction caused by the B-type whitefly harm.
1. Origin of B-type Bemisia tabaci and transmission B-type Bemisia tabaci originated in North Africa and the Middle East. In 2000, Beijing, Guangzhou, Xinjiang and other places successively appeared B-type whitefly mites.
2. The harm of B-type whiteflies can damage many kinds of crops, ornamental plants and wild weeds. The host range is more than 74 families and 500 species of plants.
1 The direct hazard is the same as the whitefly in the greenhouse. The nymphs and adults attract juice from the plants, and the plants are directly affected. The leaves are yellow and the leaves are curled.
2 indirect hazards cause coal pollution: B type whitefly and the greenhouse whitefly have the habit of gregarious and flock migration, which secretes a substance with high sugar content, after the mold, produce coal pollution Affect light transmission, reduce photosynthesis, reduce plant growth and yield.
Transmission of the virus: It can carry a variety of viral infections. At present, more than 10 viruses have been found to be the main mediators of the transmission of crop virus diseases.
Physiological and metabolic disorders of plants: B-type whiteflies secrete saliva containing harmful substances into the plants during the course of the damage, which leads to the disorder of metabolic activity in the plants, the imbalance of endogenous hormones, the inhibition of plant growth, and the appearance of chlorosis. , white, teratogenic and other symptoms.
3. Identification of B-type Bemisia tabaci The nymphs and adults of B. tabaci are very similar to the whitefly in the greenhouse, and it is difficult to distinguish them. Generally, the identification of the silver leaf reaction of summer squash is used. In the true leaf stage of 3-4 leaves of zucchini, adults or nymphs were inoculated. Under certain conditions, there was a silver leaf reaction indicating the presence of B-type whiteflies, but they could not be quantified qualitatively.
III. Prevention and treatment of silver leaf reaction
1. Comprehensive prevention and control of greenhouse squash to prevent and treat B-type niacin. Comprehensive measures such as agriculture, physics, and chemical control should be applied, focusing on five words.
1 No: First, no pests are cultivated, and pests are not allowed to enter the shed. Second, there are no worm sheds, weeds are removed before the greenhouses are planted, clean the pastures, and 1-2 days before planting, no insects escape the net. . 2 Blocking: Install insect-proof nets on vents, doors, and vents in the greenhouse, and do not allow flyheads to fly into the shed. 3 inducement: B-type whitefly has a strong tendency to orange yellow, orange-yellow sticky plates in the greenhouse can trap and kill adults, and can be used for prevention and prediction as a basis for chemical control. 4 Smoked: Once it is found to be harmful, it is smoked and smoked at night with smoke, commonly used scorpion smokers, scorpion net smokers, etc. are ignited in the evening, boring one night and releasing the next day. 5 Kill: In the morning and evening, adults lay on the back of the leaves, and they have poor ability to move. They can be sprayed with insecticides. Since the B-type Bemisia tabaci is more susceptible to resistance than the greenhouse whitefly. Therefore, attention should be paid to the alternate use of chemical agents, which can be used interchangeably with insect-like phytosteryls, pyrethroids, carbamates, etc., and each agent can be used continuously no more than twice.
2, the chemical control of nymphs from the first peak to the performance of the silver leaf symptoms early spraying can be effective control. Chemical control generally uses 20-30 mg/L of gibberellic acid + 500 times cytokinin + 5000 times double action activin mixture to control the best, 7 weeks after spraying can resume normal growth, and after 2 weeks into normal results .
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