Several methods for controlling Thrips palmi in greenhouses in Japan were compared in their effectiveness on a population model. Since a use of chemicals alone is not effective, some other methods based on cultural practices were subjected to test. They included combined practices of rotation of crops, use of cheesecloth, ultra violet absorbing vinyl film, blue sticky ribbon and/or silver film. From the simulation on the basis of population model of T. palmi, the following conclusions are derived: 1) since the low density effect functions in an influential manner, it is recommended that the insect population be maintained at a very low density level: 2) considering the importance of the safe use of agricultural chemicals, insect control relying on insecticides alone is not adequate: 3) control methods based on cultural practices are considerably effective in suppressing the population density: and 4) an adequate integration of insecticide sprayings with the cultural control method is highly recommendable.