The hypothesized visual system of Thrips tabaci Lindeman and Frankliniella occidentalis (Pergande) based on different coloured traps' catches.

Thrips tabaci Lindeman and Frankliniella occidentalis (Pergande) are the most studied members of Thysanoptera: Thripidae, since these thrips species have already become worldwide spread pests causing serious yield losses. Thrips damage host plants directly through the feeding process and indirectly by transmitting plant viruses. Biological characteristics of these species make them difficult to manage and prevent the damage they cause. This study is aimed to find the most attractive colour of the commonly used sticky traps for mass trapping of these two species, and generate information about the vision system of both specimens by investigating the reflectance spectrum of these traps. The attractiveness of white, yellow, blue and fluorescent yellow sticky traps for T. tabaci was investigated in a white cabbage field during summer production. The order of attractiveness of yellow, blue and fluorescent yellow traps was also investigated for F. occidentalis in a greenhouse during the pollination season of selected cauliflower plants. In this study number of captured thrips specimens was significantly affected by trap's colour in open field for T.tabaci (x2(3)=147,4; p<0,001) and also in the greenhouse for F.occidentalis (x2(2)=457,8; p<0,001). No significant differences were found between the numbers of the specimens of T. tabaci caught by the yellow (average 36,03 specimens per trap) and white (average 33,25 specimens per trap) coloured traps (Mean dif. 2,06; SE 3,79; Bonferroni sig. p=l,000), while the blue colour (average 18,1 specimens per trap) proved to be the least attractive. Fluorescent yellow coloured traps caught the highest number of the specimens (average 82,88 specimens per trap) of T. tabaci. The highest numbers of F. occidentalis were also caught with fluorescent yellow sticky traps (average 47,88 specimens per trap), followed by blue (average 21,67 specimens per trap) and yellow (average 9,29 specimens per trap). Thereby, fluorescent yellow traps proved to be the most effective in this study for monitoring thrips species both in the field and in the greenhouse. The light reflectance of the coloured sticky traps used in this study and the petals of cauliflower flowers were also measured both in the UV and visible light ranges. The proportion of captured thrips specimens of the two species (T. tabaci and F. occidentalis) and the light reflectance spectrum of the most preferred coloured traps suggest that these thrips species might have different photoreceptor systems. Results of this study also suggest that light reflectance in the yellow region and in the UV range has the most important effect on host plant selection of T. tabaci and F. occidentalis. [ABSTRACT FROM AUTHOR]