Research And Development Of The Key Techniques Of Campoletis Chlorideae Mass-rearing

The parasitic wasps are major forces in biocontrolling insect pests.There is severe mutually contradictory between the increasing demand for biocontrol products from society and the serious shortage of enemy products.Therefore,it is necessary to exploit effective parasitoid products.However,the process of commercialization is hindered by the insufficiency of mass-rearing techniques of parasitoids.In the present paper,a predominant larval endoparasitoid Campoletis chlorideae with fine characteristics in controlling the economic pest Helicoverpa armigera,was chosen to study the key mass-rearing techniques,including four parts,such as the selection of adequate host insect,the standard morphology of breeding parasitoid,the effect of pairing pattern on mating success rate,ways to improve fecundity,rapid molecular detection,low temperature storage,and parasitizing ability assessment.The preliminary results were showed as below.1.The selection of adequate host and standard morphology breeding parasitoidParasitism preference of Campoletis chloridea to larval instars of host Helicoverpa armigera was determined by the methods of parasitism in single or group,and choice test.Compared with other instars including the end of 1st,the beginning of 2nd or 3rd,the end of 2nd instar was the best host for C.chlorideae mass rearing due to its high parasitism rate,choice coefficient was a little lower than that of 3rd,and the most important advantage was the high yield rate,big body size,neat development and lower rearing costs.After several generations,Mythimna separata can be used as replace host to provide different nutrition for rejuvenation.We developed a number of criteria for standardization the quality of C.chlorideae mass-rearing.For example,the gray white color of cocoon,about 6.2 mm×2.1 mm size was good quality,and female adult was 6.0-7.0 mm,male 5.5-6.5 mm,Especially after rearing five breeding generations when the appearance of adult morphological deformities appeared.These abnormalities can be used as indicators to be carried out population rejuvenation.With an attempt to provide useful information for breeding and utilization of this parasitic wasp,high quality of C.chlorideae mass-rearing can be ensured according to these criteria.2.The factors affecting mating success in Campoletis chlorideaeAbundant females in population is beneficial for mass-bearing parasitoid,therefore,the first and most important thing is to ensure mating success.In the present paper,the mating behaviour and rhythm of Campoltetis chlorideae was observed firstly at different temperature treatments(12?19? or 25±2?).The mating behaviour is composed of four phases,pairing,courtship,coupling,and the end of coupling.With the rise of temperature,mating behaviour was more active,especially for females.The mating success was higher at 25±2? than that at 12?19?.The mating rhythm was higher in the morning,up to 78.9%,and then declined to 5.3%in the afternoon.After separating female body,only the existence of female reproductive organ can stimulate flapping the wings of males,this indicated that the sex pheromone was produced from female reproductive organ.Furthermore,focus on the parental age affecting mating success was investigated.The results showed that the combination of newly emerged females(<0.5d)and one day males got higher mating success,up to 57.9%,than other mating age group combinations,and obtained more offsprings.In some cases,more males can increase mating opportunity in favor of mating success,although,the interruption of mating took place sometimes.The mating success rate varied in different geographical populations.With the increasing of breeding generations,the mating success rate declined.All in all,many factors affecting mating success,from our results,the temperature,parental age,and pairing ratio,and breeding generations played role in affecting mating success rate.3.The indicators to evaluate Campoletis chlorideae fecundityMass-bearing of parasitoid should produce a maximum of good quality female wasps with high fecundity in order to provide basis for controlling insect pests in the fields.Therefore,it is very important to exploit the the indicators to evaluate Campoletis chlorideae fecundity quickly.According to the reported studies that the female fecundity was determined by body size or the number of ovarioles,we focused on maternal effect and host to research their effects on parasitoid body size,the number of ovarioles,and their fecundity.The results indicated that there were positive relationships among them.Larger females had more number of ovarioles,higher fecundity,higher gene expression of Vitellogenin(Vg)or Vitellogenin Receptor(VgR),which are related to oogenesis,and protein contents than those of smaller ones.Therefore,to evaluate the female fecundity in mass-rearing of C.chlorideae,their body size(as measured by hind tibia)can be used as a direct indicator.4.The cold storage and parasitizing ability check of Campoletis chlorideaeThe storage of parasitoid at low temperature has proved to be a valuable method to provide sufficient supply,prolonged shelf-life,and lower costs parasitoids for biological control of insect pests.Cocoons of parasitoid or parasitized host larvae were stored at 6?10?,respectively,After 3 5d,they were transferred to 25±2? in the laboratory,Obviously,after cold storage of parasitoids,a reduction of fitness traits took place,such as smaller body size,decreased vitality and fecundity.However,compared with storage of parasitized host larvae,higher emergence,bigger size were observed from coccons in which were stored.Furthermore,innovations in cold storage methods are necessary in order to produce high emergence,fecundity,rational sex ratio offsprings.To assess the parasitzing ability of rearing parasitoid is necessary,therefore,we should develop a measuring device.This device is consists of two detachable parts,including host rearing box and wasp movement box,30?50 2nd larvae of Mythimna separataone were provided to one female at 8?10 am,usually after 2 hours later,the host larvae were checked under microscope to look for the black egg under the integument of hosts.Using this method,we can rapidly valuate the parasitsm rate and parasitoid fecundity of offsprings descendants.This can provide useful technique and method for mass rearing of parasitoid.