Research On Rearing And Storage Techniques Of Telenomus Remus (Nixon)

The Spodoptera frugiperda(J.E.Smith)is a devastating invasive pest that seriously threatens maize production in China,posing a serious challenge to the development of the maize industry and national food security.The egg stage is an important window period for the management of S.frugiperda,and the application of egg parasitoids is particularly important for the long-term sustainable control of S.frugiperda.Telenomus remus(Nixon)has the advantages of excellent parasitism capacity and specific parasitic behavior against the S.frugiperda egg masses covered with scale,which makes it the dominant egg parasitoid for S.frugiperda.The establishment of mass rearing system is one of the basic and prerequisites for the successful application of natural enemy insects in biological control in the field.However,there is a lack of research on the large-scale rearing of T.remus in China,which makes it difficult to support and promote the large-scale production and application of this species.Therefore,the aim of this study was to construct a large-scale rearing system of T.remus by evaluating important biological parameters and exploring key large-scale rearing techniques,so as to provide resource supply for the prevention and control practice of S.frugiperda.The main findings are as follows:1.Alternative host screeningThe adaptability of the T.remus to three host egg species that have been used reared Trichogramma species(Corcyra cephalonica Stainton,Sitotroga cerealella Oliver,and Antheraea pernyi GuērinMēneville),and two host egg species which belong to the same family as S.frugiperda(Mythimna separata Walker and Spodoptera litura Fabricius)was observed,and the T.remus were found to prefer to parasitize S.litura eggs.Further evaluation revealed that the T.remus could parasitize and successfully complete their development on the S.litura eggs at 20-32 °C.The developmental period,developmental threshold temperature and thermal constant of each stage were similar between S.litura eggs and S.frugiperda eggs.In addition,the parasitism performance and offspring fitness of T.remus on the S.litura eggs were generally comparable to those on the S.frugiperda eggs,and even slightly better under certain temperature conditions.It was concluded that the S.litura eggs could be used as alternative hosts for the mass-rearing of T.remus.2.Mass-rearing techniques researchIn order to maximize the large-scale rearing efficiency of T.remus,the effects of key factors involved in production,such as photoperiod,host-to-parasitoid ratio,exposure time,parasitoid age and host egg age on important biological parameters such as parasitism ability,developmental time,offspring fitness,life table parameters and parasitism behavior,were systematically evaluated.The results showed that the light time during the mass-rearing process should be greater than 12 h;the host egg/parasitoid ratio should be between 14-20:1;the exposure time should be 24 h;and the mass-rearing efficiency of T.remus can be significantly improved when the combinations were 3-day-old or 4-dayold parasitoids and 0-24 h or 24-48 h eggs.3.Storage conditionsOn the premise of clarifying the key mass-rearing techniques and ensuring the progress of production plan of natural enemy products,and to further reducing the production cost,we systematically evaluated the effects of low-temperature storage on the biological parameters of S.litura eggs,parasitized eggs(1st instar larvae,2nd instar larvae,prepupae and pupae)and T.remus adults,aiming to improve the utilization rate of biocontrol materials and extend the shelf life of natural enemy products by means of low-temperature storage.The results of the study showed that the S.litura eggs could be stored at 11 °C for 9 days;the 1st instar larvae of T.remus could be stored at 14 °C for 21 days;and the T.remus adults could be stored at 8 or 11 °C for 7 days.4.Product quality controlIn this study,we evaluated the effect of successive rearing on the parasitoid population quality from different perspectives,such as morphological characters,flight ability,biological characteristics and life table parameters.The results showed that 30 generations of T.remus reared on alternative hosts did not show population degradation,and not reduce or lose the parasitism ability to the target pest,S.frugiperda egg.