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Study On The Behavior Response To The Light And Sex Pheromone And Its Application In Beet Armyworm, Spodoptera Exigua

Posted on:2014-11-13Degree:MasterType:Thesis
Country:ChinaCandidate:W J ChengFull Text:PDF
GTID:2253330401467983Subject:Agricultural Entomology and Pest Control
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The beet armyworm, Spodoptera exigua (Lepidoptera:Noctuidae), is an important agricultural crop pest, which often explodes intermittently and easily obtains insecticide resistance, so light trap and pheromone trap was applied to control this pest. Simultaneously, the two trap method usually combined to implement management, but the effect of control rarely evaluated. In the field trapping experiment, the moth exhibit rhythmic behavior to the two kinds of trap and male biased to the light trap. So the control effect of the combined trap work was evaluated. Additionally, this study clarifies the regulatory mechanism of mating communication system and the features of flight to light behavior. All these research would guide the work of pest control more economically and effectively. Main results are summarized as following:1. Regulatory level of mating communication system in malesMale behavioral responses to sex pheromone exhibit an apparent rhythm in certain types of insects. However, the rhythm-regulatory level is still unknown. In this study, the circadian rhythmicities of the behavioral response to sex pheromone and flight activity were measured to characterize the rhythm-regulatory level of the behavioral responses to sex pheromone in adult male beet armyworm, Spodoptera exigua. Field sampling indicated that the peak hourly percentages of males captured in light and sex pheromone traps were found during the later part of the night from late July to early August of2011. There was a significant positive correlation between the hourly percentages of males captured by the two methods. No significant variation among different time intervals in the olfactory responses of male antennal receptors to pheromone stimuli was found at LD15:9hours and27℃with electroantennogram measurements. At27℃in combination with LD15:9(LD), a day of constant darkness (DD1) or consecutive constant darkness (DD2), the principal period of locomotor activity in the males occurred during the scotophase and the subjective scotophase. The majority of males flew to the sex pheromone source in wind tunnel experiments during the later scotophase under LD and during the subjective scotophase for DD1and DD2. The results of a Pearson correlation analysis indicated that there were significant associations between the rhythm of the behavioral response to the sex pheromone and the rhythm of locomotor activity under the LD, DD1and DD2conditions. All these results suggested that the rhythm of the behavioral response to sex pheromone was coupled with the circadian rhythm of flight activity, endogenously regulated by circadian clocks, in adult male S. exigua.2. Mechanism of rhythmic and male biased to the lightThe moth reveals apparent rhythm and male biased during the light trapping experiment in the field. The light captured more males throughout the occurrence period. Simultaneously, females were captured before midnight but male flight to the light after the midnight. The sex ratio of the natural population was1:1by collecting larvae and feeding to pupae stage. The rhythm of flight to the light and egg-laying behavior was significant associated, more over, the females captured are mated. The rhythm of males to the light trap and mating activity was significant associated. There were no significant difference of trapping rate between males and mated female, the two of which were all significant higher than the unmated females. The results were consistent well with the field experiment. So we concluded strong activity of mated females caused by oviposition before the midnight, then captured by the light trap. However, the males’flight for searching mating after the midnight, therefore, the perk of trapping located in the rest of the night, exhibited apparent rhythm to the light trap at last. The unmated females were rarely captured because of weak locomotor activity, finally, more males were trapped.3. Evaluation of control effect by the combination of light and pheromoneLight trap could captured more males and less females independently then when coupled with sex pheromone lure, in addition, the combined trapping method capture more males than the sum when used separately. In the experiment of mating disrupting, sex pheromone could interfere with the mating of the beet armyworm within the effective range. Copulation and oviposition were most important activities for population colonization in insect. So the conclusion was light trap and pheromone used separately was a better control method for management of beet armyworm.Here we studied on regulation mechanism of behavioral responses to the sex pheromone and light in Spodoptera exigua, provided a basis for optimizing the control technology of light trap and pheromone trap, saving cost and efficient management. This work possessed referential significance and practical value for pest integrated control of vegetable...
Keywords/Search Tags:Spodoptera exigua, light trap, sex pheromone, rhythm to light, malebiased, combined control
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