Research On The Synergism Of Botanical Acaricidal Activity

Agricultural mites jeopardize seriously to fruit, beans, flowers and other crops, and caused huge economic losses. The Current acacricides are mainly chemical ones which may cause enhanced resistance to mites after long-term use, and it is more and more difficult to prevent. The botanical pesticides with low toxicity, environmental harmony and not easy to residue and enhancing resistance , has became a new field of pesticide research and development. Related reports indicate that there are thousands of botanical acaricidal active substances at the current time, but these study only limited activity,component identification,etc.,and there is rarely reported about which developed into Acaricide products.In order to develop the new efficient and environmentally friend botanical acaricide, the substance from more than 170 species of plants were screened for acaricidal activity, and based screening results ,we found two conspicuous synergist combination and finally developed two preliminary EC formulation.At the same time, a in-depth research of comparative acaricidal activity between Thymol and thyme was developed, in order to revealing the interaction relationship between the botanical substance.The specific results showed as follows:1.Taking Tetranychus cinnabarinus as the test mites, using slide dip as bioassay method,more than 170 kinds of botanical substance were screened and the result show that Thymol , Eugenol and Acetone extracts of the Kochia scoparia have the most acaricidal activity and lead to the corrected motality 64.24%,60.62% and 46.85% respectively with 2000mg/L.2. After the synergistic test of these three substance and another four ones (ZDD,ZSS,CX-1,Rotenonem) screened by the elders in the"pesticide center", two synergistic mixtures Thymol+ZDD and Thymol+ZSS were found and the best synergy ratios between them were1.59 to 1 and 3.51 to 1respectively. Co-toxicity coefficient (CTC) of these two synergistic mixtures were 162.18 and 224.80.3.Based on the best synergistic mixture, combined with emulsifier screening, two preliminary EC formulations 20% Thymol·ZSS EC (Aa-1)and 20% Thymol·ZDD EC (Aa-2)were prepared.4. Acaricidal activity of the Thymol and Thyme oil and of blends of all constituents of the Thyme oil were assessed in the laboratory condition with the slide-dip method against Tetranychus urticae, Tetranychus cinnabarinus and Tetranychina hani. The result showed that Thyme oil have a more conspicuous activity than Thymol against these three mites ,these two botanical substance have the LC50 during 762.03~822.69mg/L and 118.95~1262.30mg/L, respectively.Thymol is the most active constituents of the Thyme oil, and other putatively active constituents Terpinene,Linalool,Carvacrol and 4-isopropyl-toluene also have certain activity,but Pinene,Benzoic acid and ethyl 3,4,5-trihydroxybenzoat is almost inactive.A fact that a synergistic effect between these putatively active constituents and between actives and inactives is the reason why the Thyme oil have a more powerful acaricidal activity than Thymol.