| Research on the acaricidal plants, domestic and foreign scholars have done a lot of work and found many plants with acaricidal activity. Around the world have reported more than 2400 kinds of higher plants that have controlled harmful biological activity control, which have insecticidal activity of more than 1,000,have acaricidal activity of more than 100 species.Zanthoxylum Bungeanum Maxim., Ricinus communis L., Eucalyptus spp. and Aloe vera L. are common plant species in our daily life and rich in resources. Zanthoxylum Bungeanum Maxim. have a very good insecticidal and antibacterial activity. Ricinus communis L. have different levels of the insecticidal activity for many pests, the active ingredient is ricinine and ricin. Eucalyptus spp. have a good bactericidal, insecticidal and herbicidal activity, have the potential to develop into a biological pesticide. Aloe vera L. have antibacterial and anthelmintic activity. Its active ingredient is mainly anthraquinones and polysaccharides, the former including aloin, aloe emodin and aloesin, etc., but the latter is mainly mannan.This experiment systematically studied Zanthoxylum Bungeanum Maxim., Ricinus communis L., Eucalyptus spp. and Aloe vera L. four kinds of plant extracts biological activity against Tetranychus cinnabarinus, and finally selected aloe as the research object. This study aims to seek one or more substances from aloe have acaricidal activity, for developing green, safet and environmental friendly botanical acaricides to lay the foundation. This study mainly obtained the following results:1. Acaricidal plants screeningThis research chosed five different polarity solvent, including:water, acetone, ethanol, ethyl acetate and petroleum ether. Respectively on indoor parallel extraction for this four kinds of plant material. The plant parts used in this study were the pepper seeds of pepper and castor, eucalyptus bark and aloe leaves, a total of 19 kinds of extracts were obtained and the 19 extacts were used to determine laboratory contact toxicity against female adult mites of Tetranychus cinnabarinus. Pepper and aloe vera were screened out.Subsequently,9 extracts of these two plant were used to determine laboratory toxicity againstTetranychus cinnabarinus. The results are as follows:the LC50 of aloe acetone extract against famle adult of Tetranychus cinnabarinus were0.6335mg/mL and 0.1052mg/mL respectively at 48h and 72h. The LC50 of acetone extracts of aloe are lower than other 8 kinds crude extracts. Through the data analysis, we can conclude that the two plants species are contain secondary metabolites that have good biological activity against Tetranychus cinnabarinus, among them, aloe acetone extract have the highest acaricidal active. Reference to biological activity, safety, and several other factors, ultimately determine the aloe acetone extract for the further study object. Doing detailed biological activity assessment and bio-active guided isolation for it.2. Acaricidal activity of aloe acetone extractsAloe acetone extracts as an effective extract we studied it laboratory toxicity against different states of Tetranychus cinnabarinu. Toxicity regression analysis showed that aloe acetone extracts have strong acaricidal activity against all different states of Tetranychus cinnabarinu.The LC50 of aloe acetone extract against nymph mite of Tetranychus cinnabarinus were 0.0778mg/mL and 0.036mg/mL respectively at 48h and 72h; against larva mite of Tetranychus cinnabarinus were 0.0769mg/mL and 0.0349mg/mL respectively at 48h and 72h. In addition to, aloe acetone extracts have inhibited hatching effect against the eggs of Tetranychus cinnabarinus.3. Bio-guided isolation of acaricidal active materialBased on silica gel column chromatography separation and examination of thin-layer chromatography (TLC), this study carried out the acaricidal activity trace against Tetranychus cinnabarinus of the acetone extract from Aloe vera L. Aloe acetone extract had isolated from silica gel column after 94 collections, based on the mobility of the bands, the 94 collections were grouped into 22 fractions.Though laboratory contact toxicity against female adult mites of Tetranychus cinnabarinus,the result showed that the 11 fraction had the best acaricidal activity and its LC50 was 0.0966mg/mL at 48h.4. The biological activity of active ingredientsAfter the process of recrystallization for the 11 fraction, we get some white short needle crystal and determined its melting point is 131.7℃～132.5℃. Determined the biological activity of crystals against mites.The result were as follows:the LC50 of crystals against nymph and adult mite of Tetranychus cinnabarinus were 0.288mg/mL and 0.154mg/mL respectively; the LC50 of crystals against Panonychus citri was 0.435mg/mL at 48h. In addition, the experimental data also showed that the crystals had a good avoidance activity and inhibition of spawning effect gainst mites. All this indicated that aloe contained active material against Tetranychus cinnabarinus.
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