| Scirtothrips dorsalis Hood is an economically important pest of mango, tea and chili in China. It breaks out seriously every year and has caused great economical loss to agriculture in recent years. In order to monitor population densities of Scirtothrips dorsalis Hood accurately and provide information of scientific and timely management to reduce economical loss, we studied the color preference by quantitative method and phototaxis of S. dorsalis and picked the most attractive color and light, evaluated the effect and factors of attractive color trap in the field. The main results are shown as follows:This study used the RGB mode, combined converting RGB values to virtual wavelengths and spectral reflectance to study the color preference of S dorsalis. The laboratory tests screened eight virtual wavelength colors between480nm to620nm, and we found that the attractiveness of color with560nm virtual wavelength significantly higher than the others. And540nm,580nm and600nm colors also showed obvious attractiveness, significantly higher than480nm,500nm and620nm colors. In the field studies we screened thirteen colors between400nm to640nm. Among three tests, the numbers of the560nm color caught more yellow tea thrips than the others, in the third test it showed significant differences than the others, and in the other two tests it showed no differences with580nm and540nm colors. We took the numbers of yellow tea thrips caught on various colors and the corresponding color virtual wavelengths for regression analysis. The results indicated that there was a quadratic function relationship between average number captured on traps and virtual wavelengths in the laboratory and field tests. The optimal color virtual wavelength was around560nm. We concluded that the color with virtual wavelength560nm was the most attractive color to S. dorsalis, and colors with540nm,580nm virtual wavelengths also showed obvious attractiveness.The efficiency of attractive color was evaluated by comparing with the clapping method. And the560nm color trap proved excellent. When the population density of yellow tea thrips measured by clapping in the field was low (6-11individuals/inflorescence), the maximum average number of S. dorsalis caught on the color sticky board was479individuals/board/day. However, numbers of S. dorsalis caught on color sticky board (virtual wavelengths:560nm) and collected by clapping were not significantly correlated.The effect of background colors of black, blue and white to the attractiveness of560nm color trap was tested in the field. Among the three trials, the average number of S. dorsalis caught on the black-background, white-background, and blue-background color sticky boards had no significant difference with transparent background boards, respectively. Contrast background color did not enhance the attractiveness of the color sticky board (virtual wavelengths:560nm) to yellow tea thrip significantly.The effect of metal net to the trap was tested under6mm×6mm and2mm×2mm two apertures. We found metal net cages effectively excluded non-target organisms from the sticky traps. Numbers of non-target organisms on color boards caged6mm×6mm net were fifteen percent of uncaged controls. However, the efficiency of attractiveness to yellow tea thrips was significantly reduced, numbers of yellow tea thrips caught on color boards caged6mm×6mm net were twenty percent of the uncaged controls, and numbers of yellow tea thrips caught on color boards caged2mmx2mm net were ten percent of the uncaged controls.The study compared the effect of capture of yellow tea thrips among circular trap, equilateral triangle trap, square trap, cylinder trap and3D cross traps. The results showed that average numbers caught on the circular yellowish green sticky boards was lager than the others, but only in one trail were there significant differences. Geometrical structure traps did not show higher attractive efficacy in the test.Response of yellow tea thrip to15monochromatic lights between340nm to620nm was tested in the laboratory. It indicated that yellow tea thrip has slight phototaxis. Among340nm,360nm and380nm UV monochromatic lights, positive response rate of phototaxis at360nm light was50%, significantly higher than those at the other wavelengths. According the positive reaction rate-spectrum reaction curves with one peak occurred in wavelength rang400-620nm monochromatic lights, the highest response rate peak (23.40%) was at440nm, which was significantly higher than those at600nm and620nm, but there were no significant differences with those at the others.Response of yellow tea thrip under various light intensities of360nm monochromatic light,440nm monochromatic light and white light were tested. The phototactic response rates of yellow tea thrips to light intensities of360nm monochromatic light,440nm monochromatic light and white light respectively increased with their relative light intensities increasing. The phototactic response rates to360nm light increased slowly and could reach80%finally. The phototactic response rates to440nm monochromatic light could be described by the "S" curves and could reach54.00%finally. The responses to white light were strong and at the highest intensity the percentage could reach83.33%.The optimal color trap in color range, monitoring efficiency, background color, shapes and net cages were systematically studied based on color quantization by combination of RGB converting to virtual wavelengths and spectral reflectance. We screened the optimal color which would provide technical supports for monitoring yellow tea thrips based on color preference. It would provide supports for forecast and comprehensive treatment on yellow tea thrip. And the spectral sensitivity of yellow tea thrips were first studies in this paper based on the amendment of domestic research methods, which could provide theoretical foundation for elucidating the phototactic mechanism and establishment of the color space of yellow tea thrip, and could provide some guidance on development of monitoring devices based on phototaxis. |
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