| Intensive use of pesticides resulted in both pesticide-resistant of pests and insecticide residue in vegetables, which greatly threat to public health. Traditional biological control is mass-rearing natural enemies, then directly release in crops. But because of the short effective time and high cost, it is not widely accepted by farmers. Banker plant system is a new concept for biological control of arthropod pests. Banker plant system method combines the advantages of both conservation and augmentative biological control methods, and can sustain a reproducing population of natural enemies within a crop that will provide long-term pest suppression.Both Myzus persicae and Aphis gossypii are important pests on many species of greenhouse vegetables. Aphidius gifuensis, which is widely applied in biological control of M.persicae, is also a natural enemy of S. avenae, A. gossypii and Lipaphis erysimi. We established a banker plant system with winter wheat as banker plant, S. avenae as alternative host, and A. gifuensis as the beneficial, and tested control efficiency of M. persicae on pepper plant by this banker plant system in greenhouse. In this study, we tested(1) parasitism,oviposition behavior, olfactory response and some life history parameters of an aphid parasitoid A. gifuensis on three cereal aphids and three winter wheat cultivars;(2) parasitism,oviposition behavior and some life history parameters of A. gifuensis reared on S. avenae and M. persicae on three vegetable aphids, M.s persicae, A. gossypii, and L. erysimi;(3) fecundity and longevity of A. gifuensis on S. avenae and M. persicae;(4) effects of feeding and host deprivation on egg load and reproductive potential of A. gifuensis; and get the best release time of A. gifuensis after emergence;(5) influence of natal experience of A. gifuensis on their host discrimination ability, and natal experience had significant positive effects on the host discrimination of A. gifuensis;(6) control efficiency of ‘wheat- S. avenae- A. gifuensis' banker plant system for M. persicae in greenhouse, and optimized the release strategy. The main results are as follows:1. AK58 could be the best winter wheat cultivar as banker plant for mass rearing A.gifuensis. Female A. gifuensis parasitized significantly more aphids on AK58 and Xiaoyan22 than on Xinong979. Progeny of A. gifuensis that reared on Xinong979-fed aphids and Ak58-fed aphids had higher female ratio and larger body size than those reared onXiaoyan22-fed aphids. Parasitoid progeny developed fastest on AK58 among the three cultivars. Besides, female A. gifuensis showed stronger response to aphid-infested AK58 seedlings compared to Xinong979.2. Compared to A. gossypii, S. avenae and M. persicae were more suitable for A. gifuensis development. Aphidius gifuensis produced more mummies and adults on S. avenae and M.persicae than on A. gossypii regardless of the host of origin. When A. gifuensis was transferred from M. persicae to S. avenae, the parasitism decreased, but still more than 30%.The F1 generations from S. avenae and M. persicae were more female-biased and wasps were larger than those from A. gossypii. Although there were significant differences in development time of A. gifuensis in the three aphid species, the difference was generally shorter than one day.3. Aphidius gifuensis that exposed to M. persicae had higher fecundity and longer life span than those exposed to S. avenae. When parasitize M. persicae, one female A. gifuensis produced 286.3 ± 8.7 mummies during all life span, and they lived about 10.0 ± 0.60 days;and the fecundity and longevity were 173.3 ± 11.8 and 7.3 ± 0.30, respectively, when parasitized S. avenae.4. Aphidius gifuensis could effectively suppress the population of M. persicae on greenhouse-grown peppers, and the banker plant system method was better than augmentative release method. When initial aphid density was 10 adult per plant, there were much fewer aphids in greenhouse that released A. gifuensis than in the control greenhouse;however, the parasitism of M. persicae by A. gifuensis was less than 20% in week 5. When the aphid initial density was 6 adult per plant, the number of aphids in greenhouse that released banker plant system was always very low(about 50 per plant), and the parasitism of M. persicae by A. gifuensis reached 60% in week 6. When the initial density was 20multi-instar aphids per plant, the aphid population in the greenhouse that released banker plant systems increased during the first four weeks, and then decreased; the parasitism of M.persicae was 50% in week 7.5. Aphidius gifuensis could adjust their oviposition schedule according to host availability to a certain extent, and short time host deprivation could increase their fecundity and survival rate. Aphidius gifuensis females that deprived of hosts for two days had the highest survival rate and produced the most mummies during the seven days after host available, whereas host deprivation for 3 days induced sharply decrease in the mummy production and survival rate.Honey provision greatly increased the egg load and female survival and decelerated egg resorption when hosts were absence; when hosts available, honey provision did not affect their short term reproduction, but could enhance their long term reproduction.6. Both natal experience and host density could affect super-parasitism of A. gifuensis. The ratio of super-parasitism to parasitism of A. gifuensis was always lower on their natal host than on the new host, and this difference was more pronounced as the host density decrease.In conclusion, AK58 could be the best winter wheat cultivar as banker plant for mass rearing A. gifuensis; and A. gifuensis that reared on AK58-fed S. avenae had a high parasitism on M. persicae. Besides, the ‘wheat- S. avenae- A. gifuensis' banker plant system could effectively control M. persicae on greenhouse-grown pepper plant, and the earlier we release the parasitoid once the aphids have invaded the crop, the better control efficiency we will get. |
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