SUMMARY
Western flower thrips, Frankliniella occidentalis (Pergande) is an important crop pest and a vector of tomato spotted wilt virus (TSWV) in many areas of the world. Its feeding can cause scarring and deformations on leaves and fruit, with seedlings and soft tissue particularly prone to feeding damage. Cucumbers and other vegetable are susceptible to fruit scarring. Population dynamics of western flower thrips was monitored both in field and protected spaces throughout different methods and on different ornamental and vegetables hosts. In this paper results regarding population dynamic on cucumber greenhouse crop are presented. Studies were conducted throughout five weeks. Shaken method was used. Ten leaves from the bottom of the plant, ten from the middle, ten from the tip of the plant and ten flowers were weekly sampled. Mean temperature and treatments applications were recorded. The fallen larvae and adults were counted. Females and males were separately noted. Sex ratio influence and spatial distribution was also followed. Data analysis demonstrated that thrips preferred to feed on younger leaves situated on tip of the plant. There was a very low difference between sex ratio in leaves as compared with the one in flowers. Regarding population dynamics of thrips on whole study period the trend was of increasing, thus treatment application were less efficient and proves its high pesticide resistance character.