The active ingredient of neem insecticide is mainly azadirachtin, which is distributed in neem seeds, bark, leaves and other parts. Neem seed is the best raw material for preparing pollution-free plant pesticides and preventing chemical pesticide pollution. Azadirachtin is mainly a triterpenoid substance, which is similar in structure to hormones such as steroids and terpenoid organic compounds. Azadirachtin exhibits a high specific inhibitory effect on pests such as Orthoptera, Lepidoptera, Coleoptera, and does not harm natural enemies and is safe for higher animals. Therefore, azadirachtin is recognized as the most successful plant-derived pesticide with modern significance, and is the most suitable plant protection measure for crop overall management and integrated pest management. Dilute 1000~3000 times with 3% azadirachtin, which can be used to control many important pests on vegetables, such as greenhouse whitefly, diamondback moth, aphid, leafhopper and so on. In addition to inhibiting pests and mites, Neem extract has inhibitory effects on plant pathogens and nematodes. Neem preparations are used to control leaf spot, downy mildew, powdery mildew and other diseases of fruit trees and crops.
Insecticidal mechanism of neem extract
The active ingredient of neem extract is similar in structure and composition to many hormonal substances in insects. When the pests ingest these active components of the neem, the hormone balance in the body is destroyed, the endocrine system is malfunctioning, metabolism, growth and development disorders, dysfunction of the brain and various parts of the body, resulting in loss of reproductive function, failure to reproduce the offspring, and ultimately the number of insect populations. decline. For example, the neem active ingredients Azadirachtin, Salanin and Nimbin all have the basic structure of triterpenoids, which are similar to certain hormone hormone structures in insects. When these active ingredients enter the insect body, many insects must grow and develop. The production and release of hormonal substances are inhibited. As a substitute, these "simulated hormones" are involved in the metabolic activities of insects, causing serious damage to the growth and development of insects.
The main way of insecticidal action
The neem extract has many insecticidal active ingredients and different structures. The insect-resistant effects of different types of pests are different. Scientists at the China National Rice Research Institute believe that there are mainly the following:
1. Make pests aversive and repulsive to plants
For example, after the rice plant was sprayed with 3% neem oil at an ultra-low volume, the number of landings on the brown planthopper was reduced, showing a significant olfactory repellent effect, and the insect refused to contact the treated rice plant.
2, prevent or reduce female spawning
Neem oil, neem leaves and seed extracts have repellent effects on the laying of certain lepidopteran, dipteran and coleopteran insects, such as cotton bollworm, silkworm, and bean.
3, hinder pest feeding and normal development
The results of the antifeedant mechanism of the lepidopteran larvae of the Lepidoptera larvae showed that the larvae of the larvae of the larvae had a sensory sensor sensitive to azadirachtin, and the antifeeding principle was that the azadirachtin continuously activated the insect stalk taper. It is anorexia, and it also suppresses the signal release of the appetite-causing neurons. Treatment of larvae with different concentrations of neem derivatives can result in delayed larval molting, incomplete molting (deformity) and death in molting. For example, if azadirachtin (0.75 mg/kg body weight) is injected into the first and second instar nymphs of the American cockroach, the nymphs are deformed. Higher concentrations allow the nymphs to die. Studies have also shown that neem extract can inhibit and destroy the growth and development of pests, nymphs, eggs and mites. For example, azadirachtin can exhibit the effects of juvenile hormone or ecdysone on certain hemipteran insects. The azadirachtin is introduced into the blood-sucking scorpion worm by blood feed, and the ecdysone and the larvae are introduced in the same way. Hormone, it can be seen that it can counteract the role of azadirachtin. Studies on its mechanism have shown that azadirachtin first affects the central nervous system and its endocrine system of insects, interferes with certain delivery mediators that regulate the synthesis and release of ecdysone, interferes with the production of neuropeptides in the brain, thereby inhibiting the growth and development of insects.
4. Increasing the egg-laying power of insects and making the eggs sterile
When rice plants were treated with 6% neem oil, the egg production of white-backed planthoppers and two-pointed black-tailed spider mites was greatly reduced, and the eggs produced could not be hatched. Toxicological studies on azadirachtin interference in spawning showed that the production of egg capsules was inhibited by injecting azadirachtin into the female body of the tropical planthopper 2 to 10 days after emergence. This is mainly because azadirachtin prevents the production of juvenile hormone, thereby preventing the synthesis of egg yolk protein and the production of eggs in fat, and may also interfere with the result of yolk protein by hormone control. At this time, at the end of the egg, the concentration of ecdysone in the ovary of the treated female is greatly lower than that of the control, which is the result of interference of the neuroendocrine system. Therefore, azadirachtin acts on the neuroendocrine system, interfering with the production of juvenile hormone, ecdysone and vitellogenin, thereby reducing the amount of egg production. In addition, the neem extract can also reduce the density of the insect population by poisoning adult insects, nymphs, destroying the mating of insects and the relationship between the opposite sex, triggering the metabolism of insects and inhibiting the formation of chitin.
Azadirachtin applied to crops and its control methods
1. Greenhouse celery is used to control pests such as Liriomyza sativae, whitefly, and diamondback moth in the prosperous period, sprayed with 0.3% azadirachtin 1000 times solution, or mixed with 0.3% azadirachtin 300-500 times liquid. Foliar fertilizer spraying, or spraying other non-alkaline substances, the azadirachtin is sprayed with 1000-1500 times liquid, and the pest control can be controlled for 20 to 30 days.
2. In the morning of the morning, after the sunrise, the cabbage moth, the cabbage butterfly and the cabbage moth, which were mated in the cabbage field, were sprayed with 0.3% azadirachtin 800-1200 times in the afternoon. In the larvae of Pieris rapae and Plutella xylostella, the larvae are not scattered or 0.3% azadirachtin 1000 times solution at 1 to 2 years old; 800 to 1000 times solution at 3 to 4 years old; 500 times solution at 5 to 6 years old plus 1.8 % avermectin 1000 times liquid spray.
3, tomato, eggplant in the second spike flower buds will be opened, spray with 0.3% azadirachtin 1000, or mix with other non-alkaline fungicides , foliar fertilizer and other sprays. In the initial stage of cotton bollworm, tobacco budworm, mites, and aphids, spray with 0.3% azadirachtin 1000-1200 times, 500-800 times for the pests, and spray once every 5 days. For eggplant red spider, spray azadirachtin with urea and 1.8% avermectin 1500 times spray.
4. When the melons are planted, add 1/800 of azadirachtin in the water to prevent disease. Combine with non-alkaline fungicide and mix 0.3% azadirachtin 1200-1500 times to prevent seedling pests. . In the young stage of melon, scutellaria, and chafer, use 0.3% azadirachtin 800 times solution and 20% fenvalerate EC 2000-3000 times solution, spray once every 7 to 10 days.
5, fruit trees 5 to 7 days after fruit picking, with 0.3% azadirachtin 1000 times solution plus 0.5% amino oligosaccharide 500 times solution plus organic multi-foliar fertilizer mixed spray, spray once every 7 days, It can be used to prevent pests from borrowing from the host to survive the winter and reduce the damage of the leap year. In the spring, when the fruit trees are now 15% to 20% flower buds, 0.3% azadirachtin 500-800 times liquid is sprayed. Control leaf miner, red spider, rust tick, heartworm, sky caterpillar, aphid, etc., in the initial or prosperous period, use 0.3% azadirachtin 800 ~ 1000 times liquid + 20% sterilized ester 1500 times solution The spray is sprayed once every 7 days, and then sprayed with 0.3% azadirachtin 1000-1500 times liquid +18% avermectin 2000 times solution at intervals of 10 days, which can achieve the purpose of prevention and treatment.
6. Rice is applied to the seedbed with 0.3% azadirachtin 500 times liquid for 3 days before planting in the field, which can control the rice leaf miner, the stem borer, the stem borer and the rice water weevil during the slow seedling period. Spraying with 0.3% azadirachtin 500-800 times in the tillering period, spraying 0.3% azadirachtin 100-1500 times at intervals of 7 to 10 days, can control rice blast, rice planthopper, and rice leaf roller , rice locusts, rice blasts, etc. Mastered in the low age, egg hatching period with 0.3% azadirachtin 800 ~ 1000 times liquid spray, with 0.3% azadirachtin 500 times liquid spray during the prosperous period, and 0.3% azadirachtin 1500 ~ 2000 after 5 days of spraying One-time control of 1.8% of avermectin 2000 times solution.
7. Cotton control of cotton aphid and cotton bollworm, the focus is on the 20% cotton in the whole field, sprayed with 0.3% azadirachtin 800 times, and sprayed 0.3% azadirachtin 1200-1500 times after 5 days. In other growth stages or when there is no biopesticide prevention, cotton aphid is harmful. It is sprayed with 0.3% azadirachtin 1000 times solution + 10% imidacloprid 1000 times solution; when cotton bollworm is harmful, 0.3% azadirachtin 800 times solution is used. +1.8% avermectin 1500 times liquid spray.
8. Tobacco is sprayed with 0.3% azadirachtin 1500 times solution 5 to 7 days after planting, and sprayed once every 7 to 10 days to prevent tobacco budworm, haze and red spider. When the soot has "women's honey" on the back of each leaf, it is sprayed with 0.3% azadirachtin 1000 times solution + 10% etoilerin suspension agent 450 times solution. Tobacco budworm was sprayed with 0.3% azadirachtin in the 3rd instar; the tobacco budworm was sprayed with 0.3% azadirachtin 800 times solution + Bacillus thuringiensis WP 1500 times solution at 4th age or older, and sprayed once every 8 to 10 days.
9. Corn is mainly used to control corn borer. In the spring corn trumpet period, 0.3% azadirachtin 1000 times solution was used to drip into the bell mouth. For migration to harmful night larvae, spray with 0.3% azadirachtin 1000 times solution at 4th instar and 500 times solution at 4th age or older.
10. Add azadirachtin to the planted water when the flower is planted. During the growth period, the insects are sprayed with 0.3% azadirachtin 1500-2000 times before the insects occur, or sprayed with other non-alkaline fungicides. Control pests such as red spider, aphid, heartworm, leaf roller moth, and leaf miner on the cultivated flower in the shed. After picking a flower, use 0.3% azadirachtin 800-1000 times solution with target pesticide spray; control rose leaves Red spider, after picking flowers, with 0.3% azadirachtin 500 times liquid + 1.8% avermectin 1500 times solution, or with 0.3% odaridin 600 times liquid spray, the effect is good.
11. Tea control tea pests, tea yellow horses, tea oranges, tea leaf moths, tea rulers and other pests, sprayed with 0.3% azadirachtin 1000 times liquid from March, sprayed once every 7 to 10 days, Then spray again 1 to 8 days, 10 to 15 days. In the young age, the insects were found to be sprayed with 0.3% azadirachtin 300-500 times in time, or 0.3% azadirachtin 1000-1500 times with the target high-efficiency, low-toxic, low-residue chemical spray.
12. Urban gardens are used to control ancient and famous tree pests, and the tree is hanged. At a height of 1.5 to 1.7 meters from the surface, a drip needle containing 0.3% azadirachtin 10 to 15 times liquid is embedded in the subcutaneous layer. By relying on the flow of sap, the azadirachtin is channeled to various parts of the tree, which can kill pests inside and outside the tree and enhance the activity of the tree. Prevention and control of other tree pests, one week after the whole leaf is spread, with a total spray of 0.3% azadirachtin 1500-2000 times liquid; after spraying 0.3% azadirachtin 800-1000 times liquid at the stage of pest migration, the insect-proof environmental protection safety ,Cost-effective.
13. Root knot nematode seed treatment, mix with 0.3% azadirachtin stock solution according to 1/100 of the seed amount, and then dry and sow. When planting, azadirachtin is combined with chitosan, and 0.3% azadirachtin 800 times solution plus chitosan 500 times liquid 秧 seedling root; planting watering with 0.3% azadirachtin 1000 times solution Butanose 1000 times solution. After the seedlings are slowed down, the roots are mixed and mixed with 1000 times of each of the above agents. During the growth period of the plant, under the conditions of high temperature and high light, the leaf wilting or the growth point of the 3 leaves showed no difference in the color of the nematode. 0.3% azadirachtin 600-800 times liquid + chitosan 600-800 times liquid Tian Iggen prevention and control can receive good results.
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