Comparison Of The Biological Characteristics Between The Natural And The Laboratory Population Of The Oriental Fruit Moth, Grapholita Molesta(Lepidoptera: Tortricidae)

The oriental fruit moth, Grapholita molesta (Busck)(Lepidoptera: Tortricidae), is amajor pest of fruit trees worldwide. Many studies in the field of rearing technique forGrapholita molesta had been made for many years. In this study, differences in biologicalcharacteristics between the natural population collected from the wild and the laboratorypopulation reared more than50generations of Grapholita molesta were investigated, toestimate if the laboratory population has the evidence of degeneration, aimed to providetheoretical reference for the forecast and control of Grapholita molesta indoor research. Mainresults of this study are as follows.1. The results showed that the pupal stage of the laboratory population was extremelysignificant longer than that of the natural population, and the egg stage, larval stage andpre-pupal stage of the laboratory population were slightly longer than those of the naturalpopulation. The larval survival, pupation and eclosion rates of the laboratory population wereextremely significant higher than those of the natural population, but there was no significantdifference in egg hatch rate.2. The rate of fruits bored by the natural population was slightly higher than that boredby the laboratory population. And the rate of fruits bored by the two populations were82.5%,66.25%respectively.3. There was no significant difference in female and male pupal weight between the twopopulations which had similar eclosion duration. The peak stage of eclosion of the laboratorypopulation was dispersing and would involve a delay of about two days compared with thenatural population. The adults of the natural population started emerging in the fifth day,reached the peak stage of eclosion in the seventh day and ended in the tenth day and thelaboratory population started emerging on the sixth day, reached the peak stage of eclosion inthe ninth day and ended in the eleventh day.4. There was no significant difference in the longevity of male and female adults, as wellas the pre-oviposition stage, oviposition stage, the number of eggs laid per female and themaximum number of mean eggs laid by per day between the two populations. The number of mean eggs laid by per day present an increase-decrease tendency in the two populations,which began to lay eggs in the third day, and reach to maximum in the fifth day.5. In the natural population, the survival rate of egg under42℃for2h and4h,44℃for1h was significant higher than that of the laboratory population, while it was significantlower than that of the laboratory population under44℃for2h; the survival rate of pupa afterexposed to40℃for4h was significant higher than that of the laboratory population, but itwas significant lower than that of the laboratory population under42℃for4h; the survivalrate of adult under40℃for2h and4h was significant higher than that of the laboratorypopulation, while it was significant lower than that of the laboratory population under42℃for1h. Regression analysis showed that there was a significant negative correlationrelationship between the temperature and the survival rate of the egg, pupa and adult afterexposed to different temperatures in the two populations. The LT50of the adult in the naturalpopulation after exposed to different temperature for1h was significant higher than that ofthe laboratory population, while there was no significant difference in other treatments.6. Life table parameters showed that the population trend index (I), net reproduction rate(R0), intrinsic rate of increase (rm), mean generation time (T), and finite rate of increase (λ) ofthe laboratory population were extremely significantly higher than those of the naturalpopulation, but the time of double population size (Dt) of the laboratory population wasextremely significantly lower than that of the natural population. Therefore the survivabilityof the laboratory population was better than that of the natural population. In other words, thelaboratory population, which shows a better adaptability, had no significant evidence ofdegeneration in this study.