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Effects Of Alternative Prey,photoperiod And Temperature On Diapause Maintain, Diapause Termination And Development Of Chrysopa Pallens

Posted on:2018-11-01Degree:DoctorType:Dissertation
Country:ChinaCandidate:L Y ChengFull Text:PDF
GTID:1313330512990520Subject:Agricultural Entomology and Pest Control
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The green lacewing,Chrysopa pallens(Rambur)(Neuroptera: Chrysopidae)is an advantageous natural enemy species for both its larvae and adults can prey on many agricultural and forestal insect pests and mites,it is known as a good biological control agents.As polyvoltine insect,C.pallens enters facultative diapause as prepupae in the winter,and temperature plays an important role during its diapause regulation and growing development process.1.In order to understand the development,survival,fecundity and predation capacity of the green lacewing,Chrysopa pallens(Rambur)feeding on Megoura japonica Matsumura,the life history and predation rate were analyzed using age-stage,two-sex life table at 25°C and a photoperiod of 15L: 9D in the laboratory.The fecundity of C.pallens was 683.66 eggs/ individual.The intrinsic rate of increase,finite rate of increase,net reproduction rate and mean generation period of C.pallens was 0.1247 d–1,1.133 d–1,333.64 eggs/ individual and 46.52 d,respectively.The mean predation rate of the larva,female adult and male adult was 145.25 aphids/ predator,1 192.47 aphids/ predator and 669.08 aphids/ predator,respectively.When survival rate was taken into account,the net predation rate was 1 026.97 aphids/ predator during the total life span.The transformation rate from prey population to predator offspring was 3.08.The stable predation rate and finite predation rate was 5.49 aphids/ predator and 6.22 aphids/ predator.These results indicated that the green lacewing performed good characteristics of individual development,population growth and predation,and M.Japonica could be selected as one of preys for the green lacewing mass-rearing.2.We observed the diapause termination under different combinations of temperatures(22°C,25°C and different low temperatures)and photoperiods(15L: 9D and 9L: 15D),and the post-diapause biology including pupal duration,pupal survival rate,adult fresh weight,adult longevity,preoviposition period and number of eggs laid per female of C.pallens at laboratory conditions.The prepupal duration under the photoperiods of 15L: 9D and 9L: 15 D at 25°C(50.09 d and 49.47 d,respectively)was significantly shorter than those at 22°C(80.80 d and 82.20 d,respectively).The chilling treatment at 5°C prolonged the prepupal duration extremely significantly(P<0.01),and deceased the individual difference of prepupal duration.The prepupal duration of diapaused prepupae 1 d after cocooning in C.pallens was shorten to a variable extent after treated by-1°C~-10°C for 2 h or 4 h,and there were significant difference in most treatment.Further study was did to observe the sensitive period,and we found that the prepupal duration of 1 d,5 d or 10 d diapaused prepupae was shorten after treated at-5°C for 4 h,while the diapaused prepupae of 20 d,30 d,40 d and 50 d diapaused prepupae had no significant difference with control group.Compared with the non-diapause prepupa at 22°C,the diapaused prepupa had significantly decreased the survival rate,significantly prolonged the pupal duration and preoviposition period,significantly shortened the female adult longevity and significantly decreased the adult fresh weight and the number of eggs laid per female.The diapause duration of C.pallens was 50 d~170 d at 22°C under a photoperiod of 15L: 9D,and the post-diapause development was affected,with the pupal duration gradually prolonged,the adult fresh weight decreasing,and the male adult longevity initially increasing and then decreasing,but with no significant differences in the pupal survival rate,female adult longevity,preoviposition period and number of eggs laid per female.We concluded that the tested photoperiods have no significant effects on the diapause termination and post-diapause development and reproduction in C.pallens under the experimental conditions,and temperature is the key factor to regulate diapause development and reproduction.Higher temperature promotes the termination of diapause,while 5°C long time chilling can synchronize population diapause development.2 h or 4 h low temperature treatment of-1°C~-10°C can promotes the termination of diapause,while its sensitive period was 1 d~10 d after cocooning.There is reproduction cost in diapaused C.pallens,and diapause duration affects some of its post-diapause biological characteristics.3.The influence of fluctuating temperatures on the development and fecundity of C.pallens and two aphids,M.crassicauda and Aphis craccivora Koch,were determined by collecting life table data at a constant temperature(22°C)and two fluctuating temperatures(22 ± 3°C and 22 ± 5°C).Compared with constant 22°C,the preadult period and the female and male adult longevity had no significant difference at 22 ± 3°C,while the preadult period was significantly prolonged and the female and male adult longevity significantly decreased at 22 ± 5°C,but there were no significant difference in the fecundity and intrinsic rate of increase at 3 temperature conditions.The fecundity and intrinsic rate of increase of M.crassicauda decreased significantly at 22 ± 3°C and 22 ± 5°C fluctuating temperatures,while A.craccivora showed the opposite tendency.By studying on the cold hardness of non-diapause prepupae in C.pallens,we found that the super cooling point,fresh weight of cocoon,fresh weight and free water content at 3 fluctuating temperatures(22 ± 3°C,22 ± 5°C and 22 ± 7°C)significantly decreased with the increasing of amplitude,while fat content incressed with the increasing of amplitude.The protein content,soluble suger content and trehalase activity of C.pallens in 22 ± 3°C and 22 ± 5°C treatment was lower than 22°C,but it was opposite for trehalose content.These results showed that the effects of fluctuating temperatures were different between species,22 ± 3°C and 22 ± 5°C had no influence on the population growth rate of C.pallens population,while the cold hardness of non-diapause prepupae significantly decreased in 22 ± 5°C and 22 ± 7°C treatment.22 ± 3°C and 22 ± 5°C had negative impacts on the life history traits of M.crassicauda,but they were beneficial for A.craccivora.Data obtained at constant temperatures may not reveal accurately reflect the biotic responses of pests in the field.In addition,information obtained from life table studies of daily fluctuating temperatures might be useful in mass production of biological control agents and the pest management.
Keywords/Search Tags:Chrysopa pallens, Megoura japonica, life table, diapause, post-diapause development, reproduction, fluctuating temperature
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