Factors affecting fruit damage caused by <i>Thrips hawaiiensis</i> (Morgan) (Thysanoptera: Thripidae) in citrus lemon groves in Turkey

The Hawaiian flower thrips, Thrips hawaiiensis (Morgan) (Thysanoptera: Thripidae) is an economically important invasive species in citrus grown in the eastern Mediterranean region of Turkey. The diverse impacts of temperature on arthropods are well documented. This study was conducted with the aim of determining the influence of day-degree on insect population dynamics and crop damage levels in Mersin Province, Turkey during 2018-2019. In 2018, the first damage caused by T. hawaiiensis was observed at 300 degree-days (DD), while in 2019, it occurred at 800 DD. The damage percentage was recorded as 28% in the lemon grove, where the population of second instar larvae briefly reached a high level (approximately 2 individuals per fruit). During 2019, the average temperature remained relatively low, and the initial population density of thrips was below the 33-day development threshold (10.4 degrees C) from January to April. This pattern was observed even during the mild spring season. Additionally, in both sampling locations, the high adult densities, mainly adult females, led to the shedding of a limited number of flowers that had formed in June.