RESUMO
The aim of the present research work was to investigate the population density and species composition of thrips infesting crops of leek in south Poland. The flight activity of thrips was monitored using blue sticky traps and plant samples were taken to record the number of adult and larvae of thrips on leek. In 2004, the thrips were caught into blue sticky traps from the middle of June to the end of second decade of October. The first peak flight activity was noticed on the beginning of the third decade of July. The next peak flight activity was recorded in the middle and at the end of August. In 2004 the rapid growth of the numerousness of adult thrips was recorded at the third decade of September. The evident growth of the number of the adult thrips was continued until the third decade of October. Thrips larvae were observed from the second decade of September to the third decade of October. In 2005 the highest number of adult thrips on both cultivars was noticed at the third decade of July and this corresponded to a period of intensive flight activity. 2004, the most numerous species was Thrips tabaci Lindeman, which amounted to the 98.5% of the total number of collected thrips. The second most numerous species was Frankliniella intonsa Trybom (1.1%). In 2005, the most dominant was Frankliniella intonsa (Trybom) (78.3%). The percentage participation of Thrips tabaci Lindeman was 9.8%.