Classification and study of botanical insecticides

1 classification of botanical insecticides according to their active components, chemical structure and uses, botanical insecticides are generally divided into five categories: ① alkaloids (Alkaloids): mainly nicotine, matrine, berberine, berberine, camptothecin and so on. They act on insect pests in a variety of ways, such as poisoning, avoiding, refusing to eat, anaesthesia and inhibiting growth and development. ② terpenes (Tepenes): including pinene, monoterpenes, sesquiterpenes, diterpenes, triterpenes, etc., these substances have repellent, antifeedant, inhibit growth and development, destroy pest information transmission and mating, and have both contact and stomach toxicity. ③ flavonoids (Flavonoids): most of them exist in the form of glycosides or aglycosides, disaccharides or triglycosides, mainly rotenone, hairy rotenone and so on. ④ essential oil (Essentialkoils): this kind of essential oil not only has the functions of poisoning, repelling, refusing to feed, inhibiting growth and development, but also has insect sex hormone and luring effect, which is used to control warehouse pests, such as eucalyptus oil, peppermint oil, chrysanthemum oil, chrysanthemum oil, rue essential oil, cinnamon essential oil, lard Artemisia oil and so on. ⑤ photoactive toxin (Photoactivetedtoxicity): these substances are several times or even thousands of times more lethal to pests under light, and they are widely found in plants. Such as α-trithiophenol, polyacetylene, hypericin, coumarin, berberine and so on. In addition, there are alkanoic acid lipids, such as pyrethroid, lignans, such as ethyl ether acyl ossetin, steroids, such as achyranthes bidentata sterones, glycosides, such as tomato glycosides, etc. 2 study on botanical insecticides at present, most of the insecticidal plants in China include neem, Celastraceae, Azaleaceae, Daphneaceae, Cupressaceae and so on. Neem plant insecticides were applied earlier, among which neem (Azadirachtaindica), neem (Meliatoosendan) and neem (Meliaazeddacach) are the main insecticidal plants in this family. Melia azedarach and Melia azedarach are the main plants of neem family in China, and their effective components are tetracyclic triterpenoids-toosendanin. It was found that toosendanin mainly had antifeeding, stomach toxicity and certain growth inhibition on insect activity, and could effectively control many kinds of pests such as cabbage worm, diamondback moth and citrus mites. The insecticidal EC prepared with toosendanin as the main active ingredient has a good control effect on a variety of agricultural pests, warehouse pests and vegetable pests. Neem is recognized as an ideal insecticidal plant in the world, and its active components are mainly distributed in seeds and leaves. Dozens of limonin compounds have been isolated and identified from its seeds, among which the main active component is azadirachtin, a tetracyclic triterpenoid, which has antifeedant and growth regulation effects on insect pests. Yunnan has developed and produced a series of new pesticide azadirachtin preparations. The insecticidal active components of Celastraceae are dihydroagrofuran compounds. Tripterygium wilfordii and Celastrus angustifolia are important insecticidal plants in this family. The main insecticidal components of Tripteygiumwilfordii are wilfordine,wilforgine,wilfortrine,wil-forzine and tripterygium wilfordii, which mainly exist in the root bark. Tripterygium wilfordii has insecticidal activities such as stomach toxicity, anti-feeding, inhibiting growth and development, avoiding spawning and so on, and its efficacy is fast, which is inferior to other general botanical insecticides. Celastrusangulatus has good control effect on many pests such as Plutella xylostella, armyworm, Huangshou melon and so on. Using 0.2% Celastrus angustifolia EC developed by Northwest University of Agriculture and Forestry Science and Technology, the effective rate of controlling cabbage worm, inchworm and diamondback moth was 90%, 95% and 85% respectively. There are three highly active substances in rhododendron, III (R-III), kalmanol and Grayanotoxin-III, in which R-III is the main insecticidal active ingredient. Naoyanhua is a highly effective soil pesticide, which has the effects of contact, stomach poison and fumigation. Grinding flowers into powder can control rice bracts, rice borer, leaf rollers, leafhoppers, bugs and other pests. The ethanol extract from the root of Stellerachamaejasme (abbreviated as SCEE) has strong biological activity against Pieris rapae larvae, Asian corn borer larvae and peach aphids. Four active components (umbrella lactone, daphnetin, chamaejasone and β-sitosterol) were isolated and identified from SCEE by activity tracking method. Studies have shown that Daphne hydrocarbons, chamaejasme chromone and β-sitosterol can destroy the environment of insects and interfere with the normal metabolism of insects. Sabina vulgaris (Sabinavulgaris) is a kind of plant with special insecticidal effect, high activity and stable activity, which has high research and development value. Sabina vulgaris has the functions of stomach toxicity, anti-feeding, fumigation and so on to many kinds of pests. According to the study, the extract of Sabina vulgaris also has a certain effect on the growth and development of Helicoverpa armigera, among which the fruit extract has the greatest effect on Helicoverpa armigera. In the study of its insecticidal active components, deoxypodophyllotoxin, which is isolated, has high antifeedant and toxic activity against pests. The results showed that the extract of Sabina vulgaris could activate the activities of carboxylesterase, protease and esterase in different degrees, but strongly inhibit the epoxy effect of the main detoxifying enzymes. People pay more and more attention to the research and development of light-activated substances as pesticides. Some synthetic dyes have low toxicity to mammals, but they have strong insecticidal activity to pests under light. Compared with traditional chemical insecticides, photoactivated insecticides have many advantages, such as high efficiency to pests, biosafety to non-targets, easy to decompose in the environment, strong selectivity and so on, so they have great potential for development as a new type of pollution-free insecticides. At present, the main plant-derived photoactivated toxins are furan coumarins, β-thiophenols and polyacetylene, quinones, alkaloids derived from tryptophan and tyrosine (furan quinolinoids) and isoquinolines. At present, there are two mechanisms of photoactivated toxins: photodynamic action (Phytodynamication) and photoinduced toxicity (Photoheno-toxic). Wormwood diyne, an effective insecticidal component, was isolated from the essential oil of Artemisiasco-pariawaldstKitaib, and it was found that it had obvious light-activated insecticidal activity against Spodoptera litura. The photoactivation activities of 20 extracts from 8 Compositae crops were screened. It was further confirmed that the methanol extract from the root of marigold, the ethanol extract from the whole plant and the petroleum ether extract from flower had obvious phototoxic effect on the 4th instar larvae of Aedes albopictus and Culex pipiens quinquefasciatus. Plant essential oil is a kind of plant-derived secondary metabolites, which is an oily liquid substance with small molecular weight and can be evaporated with water vapor. Some plant essential oils have good insecticidal and insecticidal effects, and can lure, repel and inhibit the growth and development of insects. The essential oil of Artemisia annua L. has antifeeding effect on Pieris rapae larvae, and its effective component is eugenol. Artemisia annua essential oil has strong fumigation activity against four important warehouse pests, such as rice weevil, corn weevil, mung bean weevil and broad bean weevil. In addition, it was found that Artemisia annua essential oil, rue essential oil, cinnamon oil, tooth leaf yellow bark essential oil, submerged camphor essential oil and star anise had good control effect on warehouse pests. Plant essential oil not only has high activity to pests, but also has the advantages of non-toxic to humans and animals, no pollution to the environment, and not easy to produce drug resistance to pests, so it is a botanical insecticide with broad application prospects.