| Clubroot or nodule disease caused by Plasmodiophora brassicae Woron is one of the soil-borne disease all over the world.The root of crops is mainly harmded by the bacteria when the cruciferea crops has been infected. The function with absorbing and transmitting water of root and stem is suffocated. The growth of the susceptible plant is slow, dwarf and the plant can not form normal leafy ball, flower head, corm and another products organ,leading a serious decline in output, and even no harvest. Once the soil has been infected by P. brassicae, it will have carrier bacteria for a long term and will be no longer suitable for planting cruciferae crops, threatening seriously to plant cruciferous crops. At present, the controling clubroot generally rely on chemicals agent, but there is no chemicals agent which can control well it. In order to search the chemical agent with superior traits clubroot and using technology, the pesticide with good inhibitory effect on resting spore germination are filtered out from15kinds pesticide by resting spore germination test in room. Through pot and field experiments, the ability of some reagents on controlling clubroot are discussed at indoor and fileld. At the same time, the chemical agent, the best at inhibiting germination of resting spore of P. brassicae,will be conducted initially seed coating. The concentration of pesticide and film forming agent are initial screened out through a series of screening test. The results are listed as follows:1.15kinds of fungicide with the ability on inhibite the germination of P. brassicae were conducted testing for indoor toxicity and regression equation of15fungicides were established. The test results showed that:the EC50of Segway, BAS651.F and Fluazinam were the lowest, and the inhibiting effect were the best on resting spore germination of P. brassicae on Chinese cabbage. The EC50of three chemical pesticides were respectively27.98mg/L、58.24mg/L and84.55mg/L. The precedence ordering of inhibiting capacity of15kinds drugs on resting spores germination was Segway> BAS651.F> Fluazinam> Quintozene>BacillusSubtilis>Flusulfamide>Metalaxyl-Fludioxonil>Thiram>Dimethomor-ph>Metalaxyl-Mancozeb>Hymexazol>Chlorothalonil>Thiophanate-methyl>Azoxystrobin>Propamocab Hydrochloride.2. Five kinds of pesticide with inhibited well the germination of resting spore of P. brassicae were potted for testing the effecting on controlling clubroot disease.These pesticides were Segway、BAS651.F、Fluazinam、Quintozene and B. subtilis. The results were as follow:The control efficiencies of Segway and BAS651. F against clubroot in pot experiment were best in five testing reagents.Four days before sowing and three leaves and wholehearted of seedling sprayed respectively in soil, the control efficiencies of Segway and BAS651. F against clubrtoot in pot experiment were70.83%,68.18%on oilseed rape and66.99%,68.93%on Chinese cabbage. Fluazinam and Quintozene took second place, and Bacillus subtilis was the worst in five testing reagent. In the two application cases, the control efficiencies of B. subtilis against clubroot was45.84%on rape and42.72%on Chinese cabbage in pot experiment, and significant lower than another pesticides.3. The chemical agent.which was the best at inhibiting germination of resting spore of P. brassicae. and film-forming agent were conducted preliminary study of seed coating. By measuring seed germination,root length and bud length for96hours in room, the concentration of chemical agent,were preliminary determinated, were6.25g/L,3.125g/L,1.5625g/L, and the concentration of film forming agent were0.5%,1.5%,2.5%. The orthogonal test was conducted with the concentrations of pesticide and film forming agent which were selected out and different reagent seed ratio(M:M). Through indoor germination experiment and pot experiment.the best formula of seed coating which were determined preliminarily were the No.2and No.5, that the concentration of fungicide was6.25g/L, the concentration of film forming agent was1.5%. pharmacopoeia ratio was1:20, and the concentration of fungicide was3.125g/L,the concentration of film forming agent was1.5%, pharmacopoeia ratio wasl:10.The control efficiencies of two methods against clubroot in pot experiment were55.76%and56.24%.4. The field experiment was carried out with Segway、Fluazinam、B. subtilis and Flusulfamide which could inhibit the germination of the dormant spore. The test results showed that:Segway with diute1500times irrigated the root of the rape at transplanting and10d after transplanting,and the concentration of Segway irrigated the root at transplanting and Fluazinam with diute2000times irrigated the root at10d after transplanting were the best in these treatments. The disease index of rapeseed plant were25.97and25.33, and the controlling effect were41.50%and42.94%by two treatments.In two treatments, the increasing ration of the yield of rape seed were respectively28.91%and27.64%, and the control efficiencies of another tested drugs was not obvious. |
PDF Full Text Request