Advantages of plant-derived insecticides
1) Most natural plant-derived insecticides have low toxicity to mammals and are safer to humans and animals in use. For example, the acute oral LD50 of rotenone in rats is 132mg/kg; the acute dermal LD50 in rabbits. It is 1500mg/kg; the acute oral LD50 of pyrethrins I and II rats is 340mg/kg, and the acute dermal LD50 is greater than 6000mg/kg. However, these natural products contain very low insecticidal active ingredients, so they are safe for humans and animals in use.
2) It has good environmental compatibility, can be degraded naturally and rapidly in the environment, will not cause residual damage to the environment, and is relatively safe for non-target organisms. They generally only contain four elements of carbon, hydrogen, oxygen, and nitrogen. Prone to degradation in the environment. It has relatively little impact on non-target organisms, especially birds, beasts, earthworms, natural enemies of pests and beneficial microorganisms. This feature of natural plant-derived pesticides is conducive to maintaining ecological balance and is relatively safe for non-target organisms.
3) Although not all insecticides are resistant to insecticides after they are used, and not all insects are resistant to any insecticides, but due to the unique mode of action of plant-derived insecticides, harmful insects are not easy to develop resistance. This can provide enlightenment or a way to solve insects’ resistance to chemical pesticides.
4) Plant-derived insecticides and chemical insecticides can be mixed to reduce the amount of active ingredients of synthetic compounds and reduce the harm to the ecological environment and humans and beneficial organisms.
5) In some cases, it can also improve the control effect of insecticides on harmful insects and play a synergistic effect. For example, mixing star anise essential oil, cottonseed oil and prickly ash seed oil with certain insecticides can significantly improve the effect.
6) Certain plant-derived insecticides have special effects, which can interfere with the growth or reproduction mechanism of insects. For example, the precocious element of the red thistle can interfere with the development and growth of mosquitoes and prevent the formation of pupae and the emergence of adults; azalea can Hormones that control insects and make insects die by refusal to feed. For example, the artificially synthesized in the laboratory and the gypsy moth pheromone extracted and isolated from the gypsy moth female’s abdomen are identical substances and have the same molecular structure (including three-dimensional structure). ), so it has the same biological effect, and it has the ability to attract males.
7) There are abundant sources, and commercial pesticides can be developed directly from natural products. A considerable part of the commercial pesticides currently in use are natural products, and the effective ingredients of azalea preparations, rotenone preparations, and pyrethrin preparations are the secondary metabolites of plants.
2. Limitations of plant-derived pesticides
However, the effect of plant-derived insecticides on harmful organisms is also conditional, and its efficacy is affected by many factors, and there are also differences:
1) Different plant species, different growth periods and growth regions of the same plant, and active ingredients taken from different parts of the same plant often show different effects on insects.
2) The same plant-derived insecticidal active ingredient has different sensitivity to different insects and different species of similar insects, or different developmental stages of the same species of insects.
3) The bioavailability of plant-derived pesticides obtained from different solvents or extracts will also show greater differences.
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