| The parasitic wasp Cotesia chilonis(Hymenoptera)is parasitoid on rice pest of Chilo suppressalis(Walker)larvae,and is widely distributed in the world including many countries and regions at present.In China and Japan,the parasitic wasp only can parasitize the host of C.suppressalis(Walker)in the field under the natural environment,one of the most important natural enemy insect of rice stem borer.In Yangzhou,C.chilonis is one of the main parasitoids of rice stem borer,and has a high rate of parasitism.In order to determine the main parasitoid species of C.suppressalis in the area of Yangzhou and the dynamic of the parasitic wasp in the field,a series of field samplings have been conducted on the rice field in Yangzhou.At the same time,some researches have been done for understanding the breeding and other biological habits of C.chilonis.For the prevention and control of C.suppressalis,this paper selects several different pesticides and population of the parasitic wasp to determine the control effects in outdoor.The main results are as follows:1.We investigated the main kinds of the parasitic wasp in the rice field of Yangzhou during 2014-2015.The results showed that the parasitic wasp begins in early July,and is visible throughout the growth period of the rice.The kinds of parasitic wasp have Cotesia chilonis(Hymenoptera),Eriborus sinicus(Holmgren),Microgaster russata(Haliday),Chelonus munakatae(Munakata),Itoplectis naranyae(Ashmead),Gregopimpla kuwanae(Vlereck).Among them,C.chilonis,E.sinicus and C.munakatae are preponderant.C.chilonis and E.sinicus are larvae parasitoid,and C.munakatae is egg parasitoid.2.The results of investigating the parasitism rate of C.suppressalis in the rice field of Yangzhou during 2014-2015 showed that the parasitism rate of C.suppressalis in the overwintering generation is higher than the growth period of rice.The main kinds of parasitic wasp are C.chilonis,E.sinicus and C.munakatae from the overwintering generation.C.chilonis keeps low instar larvae in C.suppressalis on the overwintering.After the investigation,it is speculated that the time to enter dormancy should be between December 13,2014 and November 23,2014 in Yangzhou area.3.The study to biological characteristics of C.chilonis in the laboratory showed that there is no obvious difference to C.suppressalis on the rice and wild rice stem and feed.Breeding C.chilonis under indoor conditions,final selection of female and male ratio is 2:1 as the proportion of parasitic breeding.The cocoons of parasitoid wasp can save up to more than 20 days under the temperature of 4℃.With the change of storage time,the emergence rate of parasitic wasp will also change.The cocoon keeps at low temperature after some short time,the resistance of adult to high temperature has been enhanced,and to low temperature did not appear obvious changes.Through the experiment discovered that the ability of parasitized larva to face to pressure of low temperature is higher than no-parasitized larva,it showed that C.chilonis can improve the resistance of the host to protect their own safety in the face of adversity in winter.4.The results of different pesticides and parasitoids control experiment showed that C.chilonis has certainly protective effect to the harm of C.suppressalis in the field.After 7 days,the prevention and treatment effects start to begin,were respectively 44.5%and 44.93%.Different number of parasitic wasps brings different parasitic rates.In addition,the control effect of 7 kinds of insecticides is in turn:cyantraniliprole(15ml/667m2)>chlorantraniliprole>cyantraniliprole(10ml/667m2)>bacillus thuringiensis>chlorpyrifos>abamectin>dimehypo. |
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