| Whiteflies and aphids are the key sucking pests of Bt cotton inflicting tremendous economiclosses. A number of measures have been undertaken to establish natural enemies for suppression ofsucking pests of cotton. Only a few species were successfully established. The Encarsia formosa(Gahan) and Chrysoperla sinica (Neuroptera: Chrysopidae)(Tjeder) are the most widespread naturalenemies, frequently exploited in biological control programs for sucking pest of cotton. In cotton crop E.formosa and C. sinica has been used as a promising candidate to control whiteflies and cotton aphids.The failure of natural enemies to succeed may be due to combat with adverse and entirely newenvironment. However, banker plants provide long-term pest management system of noxiousagricultural pests by sustaining and reproducing population of natural enemies within crop. This systemconsists of a variety of plant species, which can be used as hosts for continual support of naturalenemies to suppress agricultural pests. Plant suitability (banker plant) for generalist predators areimportant for efficient mass rearing and implementing Integrated Pest Management Programmes (IPM).In this regard, we evaluated Chinese jute and Glycine max as banker plants for the mass rearing of E.formosa and C. sinica, respectively and evaluated their effectiveness in field cages in cotton crop during2010and2011near Langfang Experimental Station, Chinese Academy of Agricultural Sciences, HebeiProvince, P.R. China. Banker plants provided refugia for both natural enemies in field cages.Effectiveness of the parasitoid was investigated by monitoring weekly population counts of Bemisiatabaci, nymphs, parasitized nymphs and adult parasitoids both in banker plants treatment and controltreatments fields during both years. Whereas, efficacy of the chrysopid predator was observed byinspecting weekly population records of B. tabaci, Aphis gossypii, and C. sinica (eggs, larvae, pupaeand adult) in both banker plants and control treatments during both years. The positive correlation wasobserved between the population of E. formosa and B. tabaci throughout the season. The number of E.formosa on banker plants increased as the number of B. tabaci increased. Ultimately, significant (P <0.05) suppression in the population of B. tabaci was observed during both years. The populationdensities of adult whiteflies and nymphs were significantly higher (P <0.05) in control as comparedwith mass reared banker plants treatment. Moreover, parasitization rate was significantly higher (P <0.05) in banker plant as compared with control.However, significantly higher densities (P <0.05) of C. sinica (eggs, larvae, pupae and adults)were counted in banker plants treatment as compared with control during2011. Whereas, no significant(P>0.05) difference was found in the population densities of chrysopid larvae and pupae in bankerplants and control treatment in2010. Nevertheless, significantly higher (P <0.05) population of adultchrysopid was found as compared without banker plants field. Moreover, considerably lower populationlevels of B. tabaci were observed in Soybean banker plants during both years. Densities of A. gossypii,were significantly (P <0.05) lower in banker plant field during both years.We investigated the effect of feeding different prey species on pre-imaginal development,survival, adult longevity and fecundity of C. sinica under laboratory conditions. The prey species testedwere nymphs of Aphis glycines Matsumura, cotton aphid Aphis gossypii Glover, peach aphid Myzuspersicae Sulzer, corn aphid Rhopalosiphum maidis Fitch and cowpea aphid Aphis craccivora Koch, and eggs of the rice grain moth, Corcyra cephalonica Stainin. None of these species of prey affected thepre-imaginal survival or percentage survival of the eggs of the predator. However, eggs of C.cephalonica and nymphs of M. persicae and A. glycines were the best of the prey species tested, onthese species the pre-imaginal developmental period of C. sinica was shorter and its adult longevity,fecundity and percentage survival greater than when fed the other prey species. In contrast, when fednymphs of A. craccivora the pre-imaginal development period was longer, adult longevity shorter andfecundity lower.Flight ability is of paramount importance for the releasing of natural enemies in the field. Theenergetic cost of flight fuel biosynthesis is a likely factor contributing to the decreased fitness of theflying individuals: this kind of negative association is known as trade-off. We studied the effects offlight duration on two important life-history traits, i.e. longevity and life-time egg production, ofC. sinica females, through an experimental flight manipulation bioassay, using a flight mill apparatus. Inaddition, we assessed the potential transgenerational effects of maternal flight durations on survival andon the development of the progeny. We found experimental evidence on the negative link between flightactivity (1,2and3hours) and longevity and reproductive activity in C. sinica. We also observed that inthe progeny of the females that flew for more than one hour, the development duration of the F11stinstars was significantly longer whereas there were no significant differences between the varioustreatments for all the other recorded traits. Furthermore, the recovery capacity of the larvae implied thatdevelopment and the overall survival of the F1were not affected by the maternal flight.These findings could be helpful in defining more optimum conditions for the mass rearing of C.sinica in the laboratory as well as in the field for (IPM), programmes for various crops.
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