Frankliniella occidentalis Pergande (Thysanoptera: Thripidae), originally located in the western USA, is a worldwide feared pest organism of glasshouse crops and ornamentals today. F.occidentalis causes feeding damage and transmits plant viruses. Because of its minute size, its polyphagous lifestyle, its cryptic behavior and its short generation time, F.occidentalis is difficult to control and easily develops insecticide resistances. Therefore, essential oils could be a useful alternative to chemical insecticides. The present study examines the effects of the main component of Estragon oil 4-Allylanisole (also known as Estragole or Methylchavicol) on F. occidentalis. In tests with a Y-tube olfactometer, the odour of 4-Allylanisole (with tested concentrations being 1% and 10%) showed neither olfactory attractiveness nor repellency to F.occidentalis. Furthermore, the initial response upon direct contact with 4-Allylanisole (0.94% and 0.17%) was tested. Here, the evaluated behavioural patterns showed no significant difference to the control group. Also, compared to the control group, the thrips showed no higher tendency to avoid the component by taking off. This result adds evidence that 4-Allylanisole has no repellent effects on F. occidentalis. In addition, the feeding and oviposition activities were tested in no-choice leaf disk assays. Both parameters did not show any significant differences between the test substances (0.94% and 0.17% 4-Allylanisole) and the control substances. In contrast, bioassays that offer a choice between two leaf disks (one treated and one with control substances), showed a deterrent effect of 0.94% 4-Allylanisole. At last, possible habituation effects to 4-Allylanisole were tested. After repeated exposition to 0.94% and 0.17% 4-Allylanisole for 2x24h and 4x24h, no habituation effects could be found. Therefore, 4-Allylanisole can be pictured as deterrent, but not repellent component that does not seem to lead to habituation effects on F.occidentalis. 4-Allylanisole could possibly be used in practice.