A two-year mosquito survey focusing on Aedes koreicus in northern Italy and implications for adult trapping

Aedes koreicus (Edwards) is an invasive mosquito species, like Aedes albopictus (Skuse) and Aedes japonicus japonicus (Theobald), that has already colonized a large part of northeastern Italy and other European countries. Despite its rapid expansion, information about adult distribution and trapping is lacking. Here, we conducted a two-year longitudinal survey using adult traps to investigate the spatio-temporal distribution of Ae. koreicus and evaluated the effectiveness of three trapping devices in Latin-square experiments conducted in an urban site and a forested site. Three different traps were compared: a CO2 baited Biogents Sentinel trap (BG trap), a CO2-baited Centers for Disease Control and Prevention light trap (CDC trap) and a gravid trap baited with a grass infusion. In northern Italy, Ae. koreicus was collected from late April to early November with a peak of abundance in August. In 2015, Ae. koreicus was more abundant than in 2014 due to higher temperatures during summer. Unlike Ae. albopictus, Ae. koreicus abundance was not related to the altitude of the sampling locations in the range 241-660 m a.s.l. The BG trap and the gravid trap collected significantly more Ae. koreicus than the CDC trap in the urban site, whereas there was no significant difference between the three traps in the forested site. In the urban site, the BG trap and the gravid trap were the most effective for collecting Ae. albopictus and Culex pipiens L., respectively. In the forested site, Cx. pipiens was primarily collected by the CDC trap.