Alightment of Spotted Wing Drosophila, Drosophila suzukii (Diptera: Drosophilidae) on disks with varying visual and olfactory stimuli

Methods for trapping spotted wing drosophila, Drosophila suzukii (Matsmura) (Diptera: Drosophilidae) have not yet been optimized for detection of this devastating pest of soft-skinned fruits. Here we report outcomes of choice and no-choice laboratory bioassays quantifying rate of spotted wing drosophila alightment on 5-cm-diam sticky disks of various colors, but no odors. Red, purple, and black disks captured the most spotted wing drosophila when presented against a white background. Male and female spotted wing drosophila responded identically in these tests. Significantly more spotted wing drosophila were captured on the red and yellow disks than those presenting the corresponding gray scale for that color, proving that spotted wing drosophila perceives colors and not just level of target brightness. Purple and red are the best candidates for trap color against a light background, while clear and white are the least desirable. However, when the background was switched to black, all colors were equally acceptable to spotted wing drosophila, suggesting that background must be specified when reporting spotted wing drosophila color preference. In a choice test between non-fluorescent red and fluorescent red, there were no differences in capture between either types of red. In a no-choice test, fluorescent red disks captured significantly more spotted wing drosophila than regular, non-fluorescent red suggesting that fluorescent red can attract flies and induce alightment from a greater distance than non-fluorescent red can. When an odor was added to the visual target, the cues originating across sensory modalities interacted synergistically and increased alightment rate on the disks.