| There are a large number of microorganisms and small earth-dwelling animals in the roots of plants and the surrounding soil,including pathogens harmful to crops and underground pests,as well as beneficial microorganisms or earth-dwelling animals that can promote the growth of crops,inhibit plant pathogens and improve soil conditions.Plant roots form a network of close interactions with these organisms and the soil environment.In the process of agricultural production,the above-mentioned network is regulated by research and application of fertilizers,pesticides,fungicides and other supporting production technologies,so as to improve crop yield and quality and achieve sustainable agricultural development.In recent years,a series of effective strains of Bacillus thuringiensis(Bt)and Beauveria bassiana(Bb)have been screened out for the main underground pest grubs,but problems such as short duration of holding effect,difficulty in applying drugs in late stage and poor insecticidal effect have appeared in the application process.In view of the above problems,this study first explored the reasons for the unsatisfactory field control effects of Bt and Bb from the perspective of microbial ecology.On this basis,considering the biological characteristics of the above insecticidal microorganisms and grubs,an efficient in situ fermentation granular carrier was developed to improve the control effect of microbial pesticides on underground pests.The relevant research results are as follows:(1)The potential effects of plant root peri-soil microbial community and grub oviposition on root microbial ecology were studied by culture and culture-free methods.It was found that there were a large number of microorganisms that inhibited Bt and Bb in the soil,and the grubs eggs had a strong enrichment effect on these microorganisms.Pseudomonas and Alcaligenes isolated from the oocyte surface had inhibitory effects on Bt and Bb.(2)This study successfully prepared a particle carrier which can effectively proliferate Bt and Bb in soil.The optimized formulation of the carrier is: the ratio of raw material corn flour,peanut meal and bentonite is 1:3:2,and the water content is 20%.A single screw extruder was used to prepare the extruder.(3)Through the biological activity of larva of Holotrichia oblita and Holotrichia parallela,it was found that the granular carrier could significantly improve the insecticidal effect of Bt and Bb.In addition,the combined use of the two strains could further improve the insecticidal effect,and the corrected mortality rate of larva of the H.oblita and H.parallela increased to(74.24±5.17)% and(77.55±4.16)% respectively.(4)Further,the effect of the granular carrier on peanut germinatio n and growth were tested.The results showed that the germination rate of peanut seeds could be increased and the growth of seedlings could be promoted by applying 2 granules beside peanut seeds.The results of potted and plot experiments showed that Bt and Bb could improve the control effect of grubs and increase the yield of peanut.In summary,this study analyzed the causes of the current unsatisfactory control of grubs by Bt and Bb from the perspective of microbial ecology,and specifically developed a granular carrier that can establish local dominant communities of Bt and Bb.Further tests showed that the vector could effectively improve the control effect of Bt and Bb against grubs and promote the growth of crops.The related research results provide new ideas for the research and development and application of biological pesticides to control grubs and are of great significance for breaking the bottleneck of the current biological control of grubs. |
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