Field Suppression of Spotted Wing Drosophila (SWD) (Drosophila suzukii Matsumura) Using the Sterile Insect Technique (SIT).

Abstract

Simple SummaryThe spotted wing drosophila (SWD) (Drosophila suzukii) is an economically important insect pest that can cause significant damage to a wide range of soft and stone fruit. Growers currently use chemical insecticides and labour-intensive cultural management to reduce the economic impact of SWD. The sterile insect technique (SIT) is a chemical free, environmentally friendly and proven method of insect control: sterile males are released into a specific area, where they mate with wild females, which then produce no, or very few offspring. This study aimed to demonstrate, for the first time, the use of SIT to control SWD in field conditions without physical barriers that could significantly prevent invasion of wild SWD or escape of sterile males. Trials were carried out in open polytunnels, which are known to be extremely susceptible to invading SWD in contrast to glasshouse settings, where the enclosure minimises SWD pressure. Male SWD were made 99% sterile using X-rays and released twice per week into a 7.2 ha site growing everbearing strawberries. The method achieved season-long control with suppression of up to 91% compared with two untreated control sites. We also investigated how the wild SWD population varied throughout the season and the longevity of the released sterile male SWD. This study suggests that SIT may be a very effective, environmentally sustainable alternative to chemical insecticides for the control of SWD in commercial conditions. It also provided insights to help optimise the practical deployment of the tool.Drosophila suzukii (spotted wing drosophila—SWD) is an economically important pest of soft and stone fruit worldwide. Control relies on broad-spectrum insecticides, which are neither fully effective nor environmentally sustainable. The sterile insect technique (SIT) is a proven, effective and environmentally friendly pest-management tool. Here, we investigated, for the first time, the potential of using SIT to control D. suzukii in field conditions without physical barriers that limit insect invasion. A proprietary method of rearing and irradiation with X-rays was used to obtain males that were > 99% sterile. Sterile males were released twice per week from April to October 2021 on a site in Kent, UK, where everbearing strawberries were grown in open polytunnels. The infestation of wild female D. suzukii was monitored weekly using red sticky traps with dry lure at the treated site and at two similar control sites that did not receive sterile male releases. Releases of sterile males suppressed the wild female D. suzukii population by up to 91% in comparison with the control sites. We thus demonstrated the feasibility of SIT to achieve season-long control of D. suzukii using early, sustained and dynamically targeted releases of sterile males. This provides a promising environmentally friendly method to control this important pest.