Currently, all kinds of the disadvantages brought about by the long-term use of traditional chemical pesticides have been appeared: Excessive pesticide residues in the agricultural products, increase of human and livestock poisoning incidents, pesticide resistance of pests, sharply decrease of natural enemy pests,  disruption of ecological balance, etc. Therefore, many pesticides with high toxicity, residue and persistence have been prohibited to be used.

Since January 1st, 2007, 5 kinds of high toxic organophosphorus pesticides, including methamidophos, parathion, parathion-methyl, monocrotophos and phosphamidon, have been prohibited to be used in the agricultural industry. How to select the substitutes after these pesticides are prohibited to be used? The botanical pesticides (previously called “native pesticides”) in the biological pesticides are thought highly of now.

Currently, the varieties that have obtained the three pesticide certificates include 0.1％ rhodojaponin-Ⅲ emulsifiable concentrate, 0.3％ and 0.5％ azadirachtin pesticide emulsifiable concentrates, 2.5％ rotenone emulsifiable concentrate, 3.5％ hypertonic rotenone emulsifiable concentrate, 0.20％, 0.36％ and 0.60％ matrine aqueous solution, 0.23％ matrine emulsifiable concentrate, 1.1％ matrine powder, 10％ nicotine emulsifiable concentrate, 27％ nicotine oleata emulsifiable concentrate, 0.5％ claw field aqueous solution, 0.5％ veratrine alcoholic solution, 4.1％ and 81％ ethylicin emulsifiable concentrates and over 30 compounded preparations with these botanical pesticides as the main ingredients. The registered control objects of these pesticides are mainly the pests on the vegetable and cotton, e.g. aphid, cabbage worm, plutella xylostella, helicoverpa armigera, etc.

Then what are the advantages and disadvantages of botanical pesticides?

They have the following distinct advantages: I. As the active ingredients contained in them are natural substances, not synthetic chemical substances, with smooth degradation pathways in nature after application, there is less pollution to the environment; II. As the botanical insecticides have many insecticidal ingredients with special modes of action, it is difficult for the pests to develop pesticide resistance; III. They generally have features of strong selectivity, low toxicity to human, livestock and natural enemies and relatively low development and use costs.

The botanical pesticides also have some disadvantages, e.g. most of the compounds of natural products have complex structures and are difficult to be synthesized or the costs of synthesis are too high; The active ingredients are liable to be decomposed and the preparations have complex compositions and are not easy to be standardized; The effects of most of the botanical pesticides are slow, which leads to the situation that some farmers think that the applied pesticides don’t work. The large number of spraying times and the short residual period are not easy to be accepted by the farmers; Due to the regional plant distribution, there are many limiting factors for the selection of processing site; The plant collection is obviously seasonal.

The botanical pesticides are generally aqueous solution and are liable to be decomposed in the action of sunlight or microbes with a short half-life, quick residue degradation, and poor enrichment mechanism after ingested by animals. Therefore, pesticide hazards generally won’t be caused in case of using large amount of botanical pesticides and the pollution caused by the pesticides to the environment will be reduced correspondingly. So they are real nuisanceless pesticides. Meanwhile, the botanical pesticides also have nutrient effects on the crops and can increase the nutritional value of agricultural products. Therefore, as the demand of people on green food becomes increasingly intense, the understanding of people on the botanical pesticides becomes deeper. (Professor Xu Qiyun, Gao Yan and Hu Meiying Laboratory of Insect Toxicology, South China Agricultural University).