Study On The Biology And Diapause Of Harmonia Axyridis(Pallas) In Different Overwintering Periods In Baoding

Harmonia axyridis?Pallas?is a kind of important natural enemy insects.It has good control effect for the field pests such as aphids and have been received more and more attention.Aphids are very harmful in facility agriculture in winter,so it is urgent to develop an efficient and environmentally friendly method to control aphids.A preliminary study was carried out for the biology and diapause of H.axyridis in different overwintering periods in Baoding.After the H.axyridis enter diapause state in the natural conditions,samples were taken regularly,and then H.axyridis were mated and transferred into the artificial climate chamber with long photoperiod and optimal temperature.The pre-oviposition period,oviposition period,oviposition quantity,longevity,survival time and survival rate were observed and recorded in different overwintering periods.The ovarian development in different overwintering periods were measured and recorded to find the regularity of the diapause.And according to the recording data the protection and use of the overwintering H.axyridis in Baoding were discussed.Results were as follows:?1?The pre-oviposition period of female firstly increased and then decreased with the different overwintering stages,and peaked around the winter solstice(December 15^th),the pre-oviposition period of female was about 20 days.The oviposition quantity of female was increased gradually,the number is about 600.However,overwintering would decrease the reproduction of the females,and the quantity of oviposition would decrease compared with control.The changing trend of the oviposition period was consistent with the survival time of overwintering H.axyridis.The longevity of the females would increase because of the overwintering.The survival rate of adults was 60%at the end of overwintering,and the survival rate of females were higher than that of males.?2?As the time of overwintering went on,the length of ovariole got shorter and the size of bilateral ovaries reduced.The length of ovariole was the shortest around winter solstice,which was only 521.1?m.Then after winter solstice,the ovaries of the females developed gradually.The changes of pre-oviposition periods and ovaries in overwintering stage could prove that November was the induction period of diapause,and around winter solstice the degree of diapause was the deepest.Period from December to mid-March of the next year was the holding phase of diapause.And it was the release period of diapause from mid-March to mid-April.?3?It was the best time to use overwintering H.axyridis in Baoding from mid-January to mid-March because of relatively short pre-oviposition period,long oviposition period and longevity.Protection of the overwintering population and overwintering place of H.axyridis were needed from early winter?early November?to mid-January.This provided a theoretical reference for the protection and utilization of H.axyridis in protected agriculture in winter.