The toxicity of materials derived from rhizome of Cnidium officinale Makino to adults from B and Q biotype of Bemisia tabaci was examined using a leaf-dipping bioassay. Results were compared with those of two currently used insecticides: acetamiprid and thiamethoxam. The active principles of C. officinale rhizome were identified as butylidenephthalide (1), ligustilide (2), and 3-butylphthalide (3) by spectroscopic analysis. These compounds exhibited 100% mortality against both B and Q biotype adults at 2.5 mg/ml. At a concentration of 1.25 mg/ml, butylidenephthalide produced 88 and 92% mortality against B and Q biotype adults, respectively. 3-butylphthalide showed 100 and 89% mortality against B and Q type adults, respectively. Ligustilide exhibited 97 and 100% mortality against B and Q type adults, respectively. The toxicity of these compounds to B type adults was almost equal to that of thiamethoxam and acetamiprid, whereas two insecticides exhibited 40% mortality to Q biotype. C. officinale rhizome-derived materials merit further study as potential insecticides for the control of B. tabaci populations due to global efforts to reduce the level of highly toxic synthetic pesticides.

The toxicity of melissa and savory essential oil constituents against adult Bemisia tabaci was examined using vapor-phase toxicity bioassay. Results were compared with those following the treatment with currently used insecticide dichlorvos. As judged by 24 h LC50 values, thymol (0.59×10-3 mg/cm3) was the most toxic constituent, followed by cavacrol (0.60×10-3 mg/cm3). These compounds were slightly less toxic than dichlorvos (LC50, 0.20×10-3 mg/cm3). Strong activity was also obtained from borneol (LC50, 1.06×10-3 mg/cm3), α-terpineol (1.22×10-3 mg/cm3), geraniol (1.23×10-3 mg/cm3), linalool (1.33×10-3 mg/cm3), lavendulol (1.44×10-3 mg/cm3), nerol (1.52×10-3 mg/cm3), β-citronellol (1.81×10-3 mg/cm3), terpinene-4-ol (1.87×10-3 mg/cm3), 1-octen-3-ol (2.06×10-3 mg/cm3), and citral (2.34×10-3 mg/cm3). The melissa and savory essential oil-derived compounds, particularly thymol and carvacrol, merit further study as potential insecticides for the control of B. tabaci.