| Overuse and misuse of chemical pesticides has caused great damage to ecological environment, human health and biodiversity. So in oder to respond to the issues of chemical pesticides, China made plans of green control of crop dieases and pests and zero pesticides growth. Based on this, insect-trapping lamps and colored sticky cards as eco-alternative techniques of chemical pesticides has been popularized and applied in large-scale pest control in China. However, up to now, attention to ecological impacts related to using lamp traping and color traping on natural enemies of crop pests and non-target insects has been rather limited. As phototaxis is a common behaviour observed in many insects, and commercial tools for pest control (trap lights, colored sticky cards) lack selectivity or specificity to target crop pests, natural enemies of crop pests and non-target insects are also killed during pest trapping. it deserves more attention and study to ecological impacts of using lamp traping and color traping in large-scale pest control in China. So this paper proposed scientific questions as follows: (1) Whether phototaxis of crop pests and natural enemies of these pests have similarity in the same agricutural ecosystem or not; (2) Whether natural enemies of crop pests and non-target insects are also killed during pest trapping by using non-specific trap lights and colored sticky cards in fields or not.This paper chosen a tobacco agricultural ecosystem as research system and studied phototactic characteristics of three tobacco pests Bemisia tabaci, Nesidiocoris tenuis, Thrips tabaci and three natural enemies of these pests Harmonia axyridis, Encarsia formosa, Pachyneuron aphidis. Furthermore, this paper evaluated ecological impacts of using four kinds of non-specific colored sticky cards (yellow, blue, green, red) to natural enemies of tobacco pests and non-target pests in tobacco fields. The results are as follows:(1) B. tabaci was attracted to all fifteen monochromatic lights, which showed its broad spectral sensitivity to monochromatic lights emitting various specific wavelengths from 340 to 649nm, with peaks of sensitivity at 504nm and at 1501ux.(2) N. tenuis was attracted to all fifteen monochromatic lights, which showed its broad spectral sensitivity to monochromatic lights emitting various specific wavelengths from 340 to 649nm. N. tenuis adults showed four peaks of sensitivity at 504,568,589 and 628nm. N. tenuis nymphs showed three peaks of sensitivity at 549,577 and 628nm. Adult bugs were significantly more sensitive than nymph bugs. Significant differences were found between adults and nymphs in the phototactic responses of N. tenuis to different light intensity, with peaks of adult sensitivity of light intensity to green light (568nm) and red light (628nm) respectively at 150 and 501ux, with peaks of nymph sensitivity of light intensity to yellow light (577nm) and red light (628nm) respectively at 150 and 10lux.(3) T. tabaci was attracted to fourteen monochromatic lights, with the exception of red light (649nm), which showed a positive phototaxis to a broad spectrum of light, with peaks of sensitivity at 450 and 510nm. Among the intensities of blue light (450nm) and green light (510nm) examined, the phototactic response of T. tabaci was the strongest respectively at 100 and 2001ux.(4) H. axyridis was attracted to all fifteen monochromatic lights, which showed its broad spectral sensitivity to monochromatic lights emitting various specific wavelengths from 340 to 649nm. Adult bettles were significantly more sensitive than larvas. Phototactic characteristics among female, males and larvas have similarity to monochromatic lights. Female H. axyridis showed four peaks of sensitivity at 414,492, 504 and 568nm. Male H. axyridis showed four peaks of sensitivity at 380,492,504 and 549nm. Larva H. axyridis showed four peaks of sensitivity at 414,504,549 and 568nm. Among the intensities of blue light (492nm) and green light (549nm) examined, the phototactic response of both female and male H. axyridis was the strongest at 10lux. Male bettles were slight more sensitive to light intensity than female bettles.(5) E. formosa was attracted to all fifteen monochromatic lights, which showed its broad spectral sensitivity to monochromatic lights emitting various specific wavelengths from 340 to 649nm, with peaks of sensitivity at 340,414,450 and 504nm. Among the intensities of UV light (340nm) and violet light (414nm) examined, the phototactic response of E.formosa was the strongest respectively at 150 and 100lux.(6) P. aphidis was attracted to all fifteen monochromatic lights, which showed its broad spectral sensitivity to monochromatic lights emitting various specific wavelengths from 340 to 649nm. Female P. aphidis showed four peaks of sensitivity at 380,450,504 and 589nm. Male P. aphidis show two peaks of sensitivity, one at 450 nm and second at 628nm. Among the intensities of UV light (380nm) and blue light (450nm) examined, the phototactic response of female P. aphidis was the strongest at 101ux, and the phototactic response of male P. aphidis was the strongest respectively at 150 and 101ux. Female wasps were slight more sensitive to light intensity than male wasps.(7) Natural enemies of crop pests and non-target insects were also killed during target pests trapping by using non-specific colored sticky cards. Over half of the specimens caught were target insects (53.1%), followed by non-target pests (32.2%), and natural enemies insects (14.7%). The ratio of trapped beneficial insects and target pests was 1:4. Blue was the most attractive color for non-target insects, followed by red>yellow>green. Blue was the most attractive color for natural enemies insects, followed by yellow>green>red. For numbers of natural enemies insects caught, parasitic wasps>lady beetles>hoverflies>lacewing flies. Blue was the most attractive color for lady bettles, followed by yellow> red>green. Yellow was the most attractive color for Aphidius gifuensis, followed by green>blue>red. Yellow was the most attractive color for E.formosa, followed by blue>red>green.Main conclusions of the study are as follows:(1) Phototaxis of crop pests and natural enemies of these pests have similarity in the same agricutural ecosystem. All crop pests and natural enemies of these pests were attracted to monochromatic lights emitting various specific wavelengths from 340 to 649nm, which showed their broad spectral sensitivity to monochromatic lights. For instance, both of B. tabaci and E. formosa showed strong phototaxis at 340-380,450 and 504nm. (2) Natural enemies of crop pests and non-target insects are also killed during pest trapping by using non-specific trap lights and colored sticky cards in fields, resulting in negative ecological effect. Based on this, it will be particularly necessary and urgent to investigate the phototatic characteristics of crop pests and natural enemies of these pests and optimise such trapping devices (trap lights and colored trap cards) so they more selectively attract the target pests and not the natural enemies of these pests. Furthermore, it will be very valuable for developing specific trapping devices for natural enemies of crop pests and applying to minitoring and auxiliary increasing of natural enemy populations in the future. |
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