Detailed Explanation of the Classification and Research Progress of Botanical Insecticides
10% cypermethrin EC used 2 to 5 days before market: 2.5% deltamethrin 2 days; 2.5% kung fu EC 7 days; 5% leifuling EC 3 days; 50% pirimicarb WP 6 days; 1.8% abamectin EC 7 days; 10% kuaishadi...
1 Classification of Botanical InsecticidesBotanical insecticides are generally divided into five major categories according to the activity of their active ingredients, chemical structure and use: 1) Alkaloids: mainly nicotine, matrine, stemonine, veratramine, berberine, camptothecin, etc., which act on pests in various ways, such as poisoning, repellency, antifeeding, anesthesia and inhibition of growth and development. 2) Terpenes (Tepenes): including pinene, monoterpenes, sesquiterpenes, diterpenes, triterpenes, etc. These substances have repellent, antifeedant and growth-inhibiting effects, disrupt pest information transmission and mating, and also have contact and stomach toxicity. 3) Flavonoids: mostly present as glycosides or aglycones, disaccharide glycosides or trisaccharide glycosides, mainly rotenone, elliptone, etc. 4) Essential oils (Essentialkoils): these not only have poisoning, repellent, antifeedant and growth-inhibiting effects, but also have insect sex pheromone and attractant effects, and are used to control storage pests, such as eucalyptus oil, peppermint oil, tansy oil, garland chrysanthemum oil, rue essential oil, cinnamon essential oil, Artemisia scoparia oil, etc. 5) Photoactivated toxicity: these substances increase their killing power against pests by several times or even a thousand times under light, and they are widely present in plants. Such as thiophene-type alpha-terthienyl, polyacetylene-type capillene, quinone-type hypericin, coumarin-type methoxsalen, furoquinoline alkaloid-type berberine, etc. In addition, there are also hydrocarbon acid esters, such as pyrethrins; lignans, such as syringaresinol; steroids, such as achyranthes sterone; glycosides, such as tomatine, etc.
2 Research on Botanical Insecticides
At present, among insecticidal plants in China, the main ones studied are plants of the Meliaceae, Celastraceae, Ericaceae, Thymelaeaceae, Cupressaceae and other families. Meliaceae plant insecticides were applied earlier, among which Azadirachta indica, Melia toosendan and Melia azedarach are the main insecticidal plants in this family. Melia azedarach and Melia toosendan are the main Meliaceae plants in China, and the active ingredient of both is a tetracyclic triterpenoid compound, toosendanin. Studies have found that toosendanin mainly has antifeedant, stomach toxicity and a certain growth and development inhibitory effect on insects, and can effectively control various pests such as cabbage caterpillar, diamondback moth and citrus mites. The insecticidal EC (Shuguojing) developed with toosendanin as the main active ingredient has good control effects on various agricultural pests, storage pests and vegetable pests. Azadirachta indica is recognized worldwide as an ideal insecticidal plant, and its active ingredients are mainly distributed in the seed kernel and leaves. Dozens of limonoid compounds have been isolated and identified from its seeds, among which the most important active ingredient is a tetracyclic triterpenoid compound, azadirachtin, which has antifeedant and growth-regulating effects on pests. Yunnan has developed and produced a series of new pesticide azadirachtin formulations.
The insecticidal active ingredients of Celastraceae plants are dihydroagarofuran compounds. Tripterygium wilfordii and Celastrus angulatus are important insecticidal plants in this family. The main insecticidal active ingredients of Tripterygium wilfordii are wilfordine, wilforgine, wilfortrine, wilforzine and wilforine, mostly present in the root bark. Tripterygium wilfordii has insecticidal activities such as stomach toxicity, antifeeding, inhibition of growth and development, and repellent oviposition against various pests, and its efficacy is rapid, which is unmatched by other general botanical insecticides. Celastrus angulatus has good control effects on various pests such as diamondback moth, armyworm and yellow squash beetle. The 0.2% Celastrus angulatus EC developed by Northwest A&F University using Celastrus angulatus has an effective rate of 90% against cabbage caterpillar, over 95% against inchworm, and over 85% against diamondback moth.
In the Ericaceae plant yellow azalea there are 3 substances with relatively high activity: rhodojaponin-III (R-III), kalmanol and Grayanotoxin-III, among which R-III is the main insecticidal active ingredient. Rhododendron molle is a highly effective native pesticide and has contact, stomach and fumigant effects. Grinding the flowers into powder can control pests such as rice skipper, rice stem borer, leaf roller, leafhopper and stink bug.
The ethanol extract of the roots of the Thymelaeaceae plant Stellera chamaejasme (abbreviated as SCEE) has strong biological activity against cabbage butterfly larvae, Asian corn borer larvae and green peach aphid. Using an activity-guided method, 4 active ingredients (umbelliferone, stellerane, stellerachromone and beta-sitosterol) have been isolated and identified from SCEE. Studies have shown that stellerane, stellerachromone and beta-sitosterol can destroy the internal environment of insects and interfere with normal insect metabolism.
The Cupressaceae plant Sabina vulgaris is a plant with special insecticidal action and high and stable activity, and has high research and development value. Sabina vulgaris has stomach toxicity, antifeedant and fumigant effects on various pests. According to research, Sabina vulgaris extract also has a certain degree of influence on the growth and development of cotton bollworm, among which its fruit extract has the greatest influence on cotton bollworm. In research on its insecticidal active ingredients, one active ingredient isolated, deoxypodophyllotoxin, has high antifeedant and poisoning activity against pests. Studies have shown that Sabina vulgaris extract activates the activities of carboxylesterase, protease and esterase to varying degrees, while strongly inhibiting the epoxidation of the main detoxifying enzyme system, mixed-function oxidase.
Research and development of photoactivated substances used as pesticides has increasingly attracted attention. Some synthetic dyes have low toxicity to mammals, but under light they have strong insecticidal activity against pests. Compared with traditional chemical insecticides, photoactivated insecticides have the advantages of high efficiency against pests, safety to non-target organisms, easy decomposition in the environment and strong selectivity, so they have great development potential as new pollution-free insecticides. The plant-derived photoactivated toxins discovered so far mainly include: furanocoumarins, beta-thiophenes and polyacetylenes, quinones, and alkaloids derived from tryptophan and tyrosine (furoquinoline alkaloids) and isoquinoline alkaloids. At present, there are two theories regarding the mechanism of action of photoactivated toxins: photodynamic action (Phytodynamication) and photoinduced toxicity (Photoheno-toxic). The insecticidal active ingredient capillene was isolated from the essential oil of Artemisia sco-paria Waldst Kitaib, and it was found to have obvious photoactivated insecticidal activity against Spodoptera litura. In screening the photoactivated activity of 20 extracts from 8 Asteraceae crops, it was further confirmed that the methanol extract of marigold roots, the ethanol extract of the whole plant and the petroleum ether extract of the flowers have very obvious photoactivated poisoning effects on the 4th instar larvae of Aedes albopictus and Culex pipiens quinquefasciatus.
Plant essential oils are a type of plant-derived secondary metabolite. They are oily liquid substances with relatively small molecular weight in plants, can be distilled out with steam, and have a certain volatility. Some plant essential oils have good insect-repellent and insecticidal effects, and have certain attracting, repellent and growth-inhibiting effects on insects. The essential oil of Artemisia anethoides has an antifeedant effect on cabbage butterfly larvae, and its main active ingredient is eugenol. The essential oil of Artemisia annua has strong fumigant activity against 4 important storage pests, including rice weevil, maize weevil, mung bean weevil and broad bean weevil. In addition, studies have found that Artemisia scoparia essential oil, rue essential oil, cinnamon oil, Clausena dentata essential oil, Cinnamomum micranthum essential oil and star anise all have good control effects on storage pests. In addition to high activity against pests, plant essential oils also have the advantages of being non-toxic to humans and livestock, not polluting the environment, and pests being less likely to develop resistance, so they are botanical insecticides with broad application prospects.