| Resistance risk of insect pests to Bt rice is an important part in of environmental safety assessment of transgenic rice. Refuge is a important countermeasure to delay the insect resistance evolution. As China carries out a small farmers cultivative plantation at present, it will be very difficuh to set particular non-transgenic refugia. The pink stem borer (PSB) Sesamia inferens feeds on many non-rice host plants near/in paddy fields. It is an important pathway to utililize these non-rice host plants as natural refuge in PSB insect resistance management, However, it needs more evidence to clarify the possibility and efficiency to use these host plants as refuges. In the present study, the population dynamic and occurrence character of the PSB together with its host preferences among different hosts were studied, in order to provide theorical and practical evidence for the latent natural refuge for PSB. In addition, based on no fittable artificial diets and rearing technology, an important tool for PSB resistance study, an artificial diet was developed for rearing the PSB by an orthogonal design test. The main results are as follows:1. The occurrence character of the PSB population showed density decrease, larval development delay but pupae weight increase in transgenic crylAc-CpTI rice field comparcd with that in the non-transgenic control MH86 rice field. The spatial distribution pattern of PSB larvae period in the field showed aggregation distribution both in transgenic and non-transgenic rice field, and also can be random distribution when density is very low.2. PSB is a polyphagous pest and has not complete 4 generations each year in ricc-growing areas of Fuyang, Zhejiang province. It was found on 5 crops (including rice Oryza sativar, water-oat Zizania latifolia, maize Zea mays, sorghum Sorghum vulgare, sugarcaneSaccharum sinensis), and 9 weed hosts (barnyard grass Echinochloa crusgalli. narrow leaved cat-tail Typha angustifolia, late juncellus Juncellus serotinus, googsegrass Eleusine indica, sloughgrass Beckmannia syzigachne, dropping wheatgrass Roegneria kamoji, leersia rice Leersia hexandra, dallas grass Paspalum distichum, reed Miscanthus sacchariflorus). The dominant hosts of PSB varies by generations. The 1st generation mainly damage water-oat, narrow-leaved cat-tail, rice, sorghum, spring maize. Most PSB of 1st generation live on non-rice hosts as the sowing area of rice is less when PSB occurs in peak period. Other generations most live on rice as rice is the main plant in ecosystem and growing along the season although the density on rice is not the highest. The development of PSB differs among the hosts but lap over. It is suggested that there are ecological environment for PSB transfer between rice and non-rice hosts between generations or within a generation in natural fields conditions.3.20 days' survival of PSB larvae feed on 8 plants showed that PSB survives better on 4 crop hosts (rice, water-oat, corn, sorghum). It survives highest on rice and develope fastest on water-oat. Oviposition choice by rice, water-oat, maize, sorghum, barnyard grass, narrow-leaved cat-tail showed no significant difference among the hosts except no eggs on the narrow-leaved cat-tail, Host choice in field experiment showed no density difference among the hosts within the 2nd and 3rd generationin, but significant difference was found in the 4th generation. Highest density were found on water-oat with significant different than other hosts, then rice, narrow-leaved cat-tail, barnyard grass. There is no significant difference of density among the three hosts. No PSB, was found on sloughgrass and cutgrass.4. By 5 batches and 144 treatments orthogonal experiment, the optimal artifical diet for PSB was developed, whose composition was as follows, corn 8g, soybean 7g, wheat germ 6g, rice stalk 2g, water oat 6g, brewers yeast 9g, casein 5g. sucrose 5.5g, cellulose lg, cholesterol 0.04g, Wesson's salt lg. ascorbic acid 0.8g, agar 4g, sobic acid 0.8g, chloramphenicol 0.04g, distilled water 200g. The diets had a better rearing efficency, on which a putation rate of 40.9ï¼…was obtained. But it is still not as good as the rearing efficency on natural host water oat. It needs further studies to optimize the artificial diet.
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