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The Occurrence, Damage And Diapause Character Of Grapholitha Molesta (Busck)(Lepidoptera: Tortricidae) In Taian Peach Orchard

Posted on:2014-07-13Degree:MasterType:Thesis
Country:ChinaCandidate:T T GuoFull Text:PDF
GTID:2253330425478178Subject:Agricultural Entomology and Pest Control
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The oriental fruit moth, Grapholitha molesta Busck, is an important fruit tree pest insectin peach and other orchard of north China. Earlier researches found out that it did the mostserious harm to peach in Feicheng, Tai’an. In this study, we investigated the populationdynamics and damage of G. molesta in Tai’an monoculture and polyculture peach orchard,contrasted developmental durations of each insect stage between natural and experimentalpopulation of G. molesta, explored the physiological and biochemical mechanisms aboutdiapause and environmental factors which affect diapause termination in G. molesta Busck.The present study aims to improve the forecast level and formulate scientific and reasonablecomprehensive prevention and control measures. Main research contents and results are asfollows:1. Population dynamics and damage of G. molesta in Tai’an districtDuring the investigation, G. molesta had five generations in one year from late March tolate September in both monoculture and polyculture peach orchard. There was obviousgeneration overlap among the second, third and fourth generation. Time of occurrence wasslightly different between2011and2012, and in polyculture peach orchard it occurred laterthan the monoculture one. Atmospheric temperature’s height and change had a significantimpact on the overwintering, firth and fourth generation. At the same time, atmospherictemperature changed during2011to2012, which affected population’s occurrence time andnumber as well. In addition, besides pesticide control methods, sex pheromone also had effecton decline in population quantity.The percentages of shoot tip damage and fruit damage increased with time, and therewere significant differences among the months in both monoculture and polyculture peachorchard. In monoculture peach orchard, the percentages of shoot tip damage was higher in oldpeach orchard than the young one. Moreover, the percentages of shoot tip damage inpolyculture peach orchard exceeded that in monoculture peach orchard. There were nosignificant differences in shoot tip damage spatial distribution on the trees, while thedifferences in the fruit damage spatial distribution were significant. 2. Developmental duration of each insect stage between natural and experimental populationof G. molestaThe results showed that, the natural population’s larva stage (9.28d), female lifespan(16.68d)and male lifespan(13.78d) were slightly shorter than experimental population’s(11.03d,17.58d and14.84d separately). While, experimental population’s prepupa stage(2.29d) and pupa stage (6.55d) were slightly shorter than natural population’s (2.61d and6.89d separately). Furthermore, female lifespan was longer than male lifespan in bothpopulations.3. Physiological and biochemical mechanisms about diapause and environmental factorswhich affect diapause termination in G. molestaThis paper has measured super-cooling point (SCP) and freezing point (FP), content offree-water, total-fat, glycerin, trehalose, glycogen and protein, and activity of CAT, POD andSOD between non-diapause and diapause larva of G. molesta. It turned out that, cold tolerancerised after diapause. The content of total-fat, glycerin and trehalose were higher in diapauselarva, while the free-water, glycogen and protein’s content decreased after diapause.Diapaused larva’s CAT and SOD activity improved, but POD activity descended. The abovecontent showed that after diapause, G. molesta larva accumulated a variety of cold hardinesssubstance to enhance their resistance to adverse situation.During the process of diapause termination, expect for their metabolic activity,environmental factors (such as photoperiod and temperature) play an important role. Thisstudy found that in20℃and26℃, the rate of diapause terminationrose with light hours’adding, it was lowest in9h light and highest in full light. As the light hours increased, thetime required to terminate diapause became shorter. On the other hand, under the condition of15h light, diapause termination time came shorter with the rise of temperature. The rate ofdiapause termination increased along with the temperature ascension, from the lowest83.33%(at17℃) to the highest100.00%(29℃).
Keywords/Search Tags:Grapholitha molesta Busck, Tai’an peach orchard, developmental duration, diapause, physiological and biochemical mechanisms, diapause termination
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