The Hawaiian flower thrips, Thrips hawaiiensis (Morgan) (Thysanoptera: Thripidae), is a polyphagous and widespread pest in tropical and temperate regions. In 2015, T. hawaiiensis was detected in lemon orchards from Turkey. In this study, the seasonal trend, damages in lemon fruit and potential alternative host plants were studied in three lemon orchards from 2018 to 2019. Thrips hawaiiensis density started to increase after petal fall and peaked in mid- or late May. A few T. hawaiiensis adults were collected in mid-June. The highest percentages of scarred fruits were 36% and 28% in 2018 and 2019, respectively. The critical period to control T. hawaiiensis was determined as 3–5 weeks after petal fall. During this period, the fruits are about 2–3 cm in diameter, and are susceptible to the thrips feeding activity.