Distribution and population development of harmful Lygus (Hemiptera: Miridae) species in cotton crop in Diyarbakır province and their relationship with plant phenology

Cotton (Gossypium hirsutum L.) is an important industrial plant in Turkey, and Southeastern Anatolia region is the top cotton producing region in the country. Several diseases and pests infest cotton crop, incurring significant quantitative and qualitative losses. Among these pests, Lygus species cause significant losses starting from vegetative period of cotton. This study determined the relationship between population dynamics of Lygus species and phenology of cotton in Diyarbakır province during 2020 and 2021. For determining Lygus species, samples were collected from 244 fields in 7 districts of Diyarbakır province by using either D-Vac. or sweep net based on the phenological period of cotton. Population dynamics studies were carried out weekly in two different fields in Sur (Gencan village) and Çınar (Şükürlü village) districts in each year, starting from 3-5 leaf growth stage of cotton. Two species, i.e., Lygus gemellatus (HerrichSchäffer) and Lygus pratensis (Linnaeus) were identified during the study. Among these species, Lygus gemellatus was the most dense and widespread, found in 91.2% and 74.7% of the surveyed fields during 2020 and 2021, respectively. The pests were recorded in cotton fields at the end of May (before the flowering period) in both years. It was observed that population increased after this period and L. gemellatus population reached the highest level during boll setting period. On the other hand, population of L. pratensis peaked during boll maturation period. Besides, it was also found that D-Vac. caught more tarnished plant bugs than the atrap method and usable fort the pests survey. It is concluded that population density of both pests can change from year to year depending on biotic and abiotic factors. It is suggested that surveys to detect these pests must be conducted at the start of vegetative period of cotton.