An invader supported by a parasite: Mistletoe berries as a host for food and reproduction of Spotted Wing Drosophila in early spring

The Spotted Wing Drosophila (SWD), Drosophila suzukii Matsumura, an invasive pest species in Europe and the Americas, is able to feed and reproduce on numerous fruit crops and a wide range of wild host plants. SWD is thought to overwinter outside of agricultural fields in forests and hedges. To identify overwintering sites and early spring oviposition hosts, traps were installed in forests. In spring 2015, traps in the canopy of pine trees parasitized by mistletoe, Viscum album subsp. laxum, captured significantly more SWD than traps in pine trees without mistletoe. We found SWD females with ripe eggs coinciding with ripening and ripe mistletoe berries. We investigated whether mistletoe may serve as a host for SWD. Under laboratory conditions, SWD developed from egg to adult in mistletoe berries. More adults emerged from wounded berries. Females were observed to feed on berries and survived up to eight days without other food. A few adults emerged from wild mistletoe berries. To understand the attraction of SWD to parasitized trees, we analyzed the volatile organic compounds (VOCs) collected from the headspace of mistletoe berries by GC–MS and identified the main components. Thirty-two VOCs were found. Wounded and unwounded berries differed significantly in the quantity of 11 VOCs emitted. The odor spectrum showed many similarities to other typical berry odors. The combination of field surveys and laboratory assays identified a new reproduction host for SWD in spring. This host plant may help SWD to withstand the bottleneck period for survival in winter and spring.