11Drosophila suzukii has become a major threat for soft fruit production of berries, plums, peach, 12 and grapevine in Europe and other regions worldwide. D. suzukii uses a wide range of different 13 coloured fruits for reproduction. Currently, monitoring is conducted with baited cup-style traps. 14 This is a laborious task and consequently is not widely deployed. Therefore, photographable and 15 toxin baited sticky traps were suggested as an alternative trapping system. The color preferences 16 were evaluated across nine sites on eight crop varieties before, during and after harvest time. This 17 study identifies red as a significantly more attractive colour for sticky card traps under natural field 18 conditions in various fruit crops during harvest time. The results demonstrate that crop and the 19 harvest-state are factors influencing the color choice of the insect. Before and after harvest no color 20 preference could be identified. The field-derived data suggest various reasons for colour 21 preferences such as trap colour (1) contrast with the environment, (2) association with fruit colour 22 and (3) ripening state. The multitude of influencing aspects shaping the interpretations are 23 discussed. 24 25 Introduction 31 Drosophila suzukii Matsumura (Diptera: Drosophilidae), also known as the spotted-wing 32 drosophila is a species native to Eastern Asia including Japan. In Europe and America it is an 33 invasive pest threatening soft fruit production 1,2 . In contrast to most other Drosophila spp. that 34 develop only on overripe or decaying fruits, D. suzukii is attracted to and can deposit eggs in 35 undamaged, ripening and ripe fruit due to the female's serrated ovipositor. D. suzukii is extremely 36 polyphag. It feeds and/or reproduces on a wide range of hosts including various soft-skinned fruit 37 crops like cherries, plums, grapes and various berries and additionally, numerous non-crop plants 38 such as wild blackberries, wild strawberries, elder, and rosehip 3-5 . Poyet, et al. 5 conducted an 39 extensive study of hosts in Europe and found that almost half of the tested plant species belonging 40 to 17 families allowed full development of D. suzukii. These species provide fruits during the whole 41 growing season, ensuring temporal continuity in resource availability. They suggested fruit traits 42 such as structure, color, shape, skin texture, diameter, weight, and phenology potentially influence 43 oviposition choice. D. suzukii may use both olfactory and visual cues 6 to find fruits. 44 45 Monitoring 46Cup style traps containing a wine-vinegar mixture to imitate the odour of fruits are used to 47 monitor the population. A recent study proposes that D. suzukii are visually attracted to darker 48 colors such as red, black and purple when presenting coloured disks on a white background and 49 that D. suzukii can separate the spectral composition of a stimulus from its overall intensity 7 .
50Additional studies with coloured baited cup traps or lids suggest a colour preference of red and 51 bla...
