Spotted Wing Drosophila (Drosophila suzukii) in Arkansas: Winter Morphs, Wild Hosts, and Fungal Control

Drosophila suzukii (Matsumura), or spotted wing drosophila (SWD), is an invasive fruit fly pest that was first found in the United States in 2008. Unlike native Drosophila, SWD females have a serrated ovipositor that allows them to attack ripening fruit. Since its introduction, it is unclear how and where they overwinter in Arkansas, what local hosts they utilize and what potential alternative tactics can be used to combat this pest. In states north of Arkansas, winter morphs (WM) of SWD are larger, darker pigmented, and can survive colder temperatures than SWD flies found in the summer. These WM were found in a wide range of alternative fruited hosts during the winter. Many researchers have begun to evaluate efficacy of entomopathogenic fungi against this pest. The objectives of this study were to determine if WM were present in Arkansas; how long into the winter months could SWD be captured and what alternative resources did they utilize in Arkansas; and if Beauveria bassiana was effective against this pest. Trap collections from May and October (2015-2017) contained WM female SWD adults that were darker and larger than flies caught in traps from June-August (2015-2017). SWD baited traps were set out from October 2017-May 2018 to see if and how late SWD appeared in Arkansas. Adults were caught until January 2018. Alternative fruit resources they used into the fall and winter months were Phytolacca americana L., Lonicera sempervirens L., Rhamnus caroliniana (Walter) A. Gray, Lonicera maackii (Rupr.) Herder and Callicarpa americana L. (purple). In the spring, the only alternative host that SWD utilized was Morus rubra L. Contact sprays of B. bassiana strain GHA at rates from 2.2 x 106 to 2.2 x 108 spores per ml killed \u3c 2% of SWD flies. This knowledge will help us better understand how SWD is surviving the winter months in Arkansas and the need to conduct future evaluations of other strains of B. bassiana on SWD