The Screening Of Bt Soil Granule For White Grubs Control

White grub has become an important underground pest in the world. Not only d id it damage peanuts, soybeans and other crops, but also for some crops(such as wheat, corn, etc.) losses.; According to statis tics, the area which grubs hazarded in our country had mor e than one million mu. For grub control, we curr ently relied on chemical pestic ides agr iculturally, but the lar ge number of applic ations of chemic al pestic ides had also brought a ser ies of problems, mainly caused by dr ug r es idues which it was easy to cause livestock poisoning. T her efor e the us e of s afe, effective and insectic idal specif ic ity of biopestic ides such as Bacillus thuringiensis( Bt f or short) to prevent and treat grubs have great prospects and advantages. In the growth process, Bt produce vegetative insectic idal pr oteins( Vip protein) and ins ecticidal crystal proteins( Cry proteins) having a specif ic insect insectic idal activity, and they ar e safe and harmless to humans and animals, so they get a w ide range of applications in the biologic al control. Exis ting commercial Bt ins ectic ide mainly for Lep idoptera, Dipter a and other pests, and has als o achieved gr eat success on their applic ation in pest control; but for Coleoptera ins ects, the Bt insectic ides is still in a blank stage. In order to enhancing the eff ect and reducing the pr ice of Bt ins ecticide, we performed a ser ies of research on a new kind of Bt insectic idal agents that is for the control of undergr ound pest, white grub.In this study, we f irst ly constr ucted a Bt185-gfp str ain, in which we connected the gfp gene to the express ion vector pST K, thus Bt185 could expr ess green fluor escent protein in the vegetative phas e us ing Pcry3Aa7 promoter. It was easy to count up the number of Bt185-gfp str ain colony.In the meantime, we screened the medium which were suitable for Bt pr olif eration. In the eight nutr ient-r ich substances, the results show that the growth effects of Bt in peanut meal was the best. At the same time we conducted a microscopic obser vation and SDS-PAGE analys is with the crystal protein which t he Bt str ain produced on peanut-meal med ium. T he r esult showed that Bt strain was capable of producing complete crystal(the crystal of Bt185 str ain was spher e and the crystal of HD73 strain was diamond.) and the protein bands were clear. Thus the peanut meal medium did not affect the production and r elease of Bt crystal protein.Further we quantitatively analys es the pr olif eration of Bt in peanut-meal medium, the liquid fermentation r esults found that under the condition of low concentration( 0.5%, 1%) unit mass nutr ients obtained the number of living bacter ium was 1816.67 × 108 cfu/g, the r esult was no signif icant differ ences at P < 0. 05 level with LB medium which was labor ator y commonly used. Later, peanut pr essed into gr anules after joining Bt spore powder, and counted the changes in the quant ity of Bt living bacter ia of gr anules in ster ile condition and in the soil which is the bacter ia envir onment. Results showed that the quantity of Bt living bacter ium in the granules were signif icantly increas ed both in two kind of envir onments : the Bt in granules can multiply 30 times, and the highest number of living bacter ium was 10.35 × 107 cfu of every grain under the ster ile condition; the Bt in granules can multiply 40 times, and the highest number of living bacter ium was 3.90 × 107 cfu of every gr ain in soil.At the same time, in the labor ator y we insectic idal activity assay to white grub used the granules that was added to the Bt185 spore powder, which had better insectic idal activity to H. parall ela larvae. The bioass ay results showed that, when tr e ating H.parall ela by gr anules w ith same initial amount of Bt, the granules insectidal activity increased from 19% to 61% by adding peanut meal. Thus it greatly improved the insectic idal activity and have the numer ous applic ation potentiality.At the same time, because ther e were a large number of bacter ia in peanut meal, the study introduced expans ion technology which was easy to process, can remove most of the peanut meal mixed bacter ia, and bacter ial removal rate r eached 86.32%. In 1% concentration, ther e was no signif icant difference between expanded peanut-meal and autoc laved peanut-meal, thus expans ion technology was a ver y good way for peanut-meal. In addition, we tested the growth s ituation of sever al bio-control strains in peanut-meal medium, which c ould control the soil- borne disease effectively. The results showed that peanut meal can not only provide nutr ients to Bt gr owth, but also to gr owth of M etarhizium anisopliae, B acillus amyloliquefaciens, Bacillus subtilis, Bacillus at rophaeus and Trichoderma spp., which pr ovides a new idea for the rational use of peanut meal and the res earch and development of biological agents.This paper focused on gr anules which could control grubs. We selected peanut meal for grown of Bt in soil, which achieved the purpos e of effective multiplic ation in granules and improved the insectic idal eff icacy of Bt granules. Thus those provided a new idea for the rational us e of peanut meal and the research and development of biologic al agents and had a high potential for applic ation.