Field competitiveness of Aedes albopictus [Diptera: Culicidae] irradiated males in pilot Sterile Insect Technique trials in Northern Italy

Vector-borne diseases account for 17% of infectious diseases, leading to more than one million deaths each year. Mosquitoes are responsible for 90% of the casualties and alternative control methods to insecticides are urgently needed, especially against Aedes vectors. Aedes albopictus is a particularly important species, causing major public health problems because it is a vector of several arboviruses and has a strong invasive behaviour. Various genetic control methods have been proposed to be integrated into the management strategies of Aedes species, among which the sterile insect technique (SIT), which proved efficient against various insect pests and vectors. However, the ability of released irradiated sterile male mosquitoes to compete with their wild counterparts and induce sterility in wild females, which is critical to the success of this strategy, remained poorly defined. Here, we assessed the field competitiveness of Ae. albopictus irradiated male using data from six release trials implemented in Northern Italy for three years. Sterile males were capable of inducing a good level of sterility in the wild female population, however with high variability in time and space. The field competitiveness of the released males was strongly negatively correlated with the ratio of sterile to wild males. This should be taken into consideration when designing future programmes to suppress field populations of Aedes mosquitoes.