| Tobacco bacterial wilt caused by Ralatonia solanacearum was a plant bacterial disease through soil infection, and it was one of the impaotant tobacco diseases in tropic, subtropics and some warm areaes. In china, the desease was generally occurred in Yangzte River catchment and the south of Yangzte River. It was broke out seriously and caused dissolvingly loss. At present there had not effective bactericide for this disease controlling. The reasons of the situation about disease controlling included 2 sides: 1) laggard study on bactericide exploiture which led to lack of agent for disease controlling; 2) weakness technology of bactericide application on control of the disease. Hereby, this study bases on the principle of plant diseases ecological control, choose for effective bactericides from various biologic agent, chemical agent and their mixtures through plate culture experiment, pot culture experiment and field experiment for evaluating the control effects of various bactericides and getting the effective mixtures. In addition, the study discussed the influencing factors on bactericide's control effect, and the application technique. According to the study, we were looking forward to gain the ideal mixtures to control tobacco bacterial wilt and felt out the scientific applied technique of these mixtures. The detailed experimental results were as follows:1. Restraining effect of bactericides and their mixtures on Ralatonia solanacearumThe results of plate culture experiment showed: Jinggangmycin, Thiodiazole-copper and Qingkuling have no restraining effect. Jinggangmycin, Thiodiazole-copper, Qingkuling mixed with Agro-streptomycin had no synergism, Qingkuling mixed with Agro-streptomycin brought on antagonism. Biologic agent pszh9944,HY96-2 have some restraining effect on Ralstonia solanacearum,but it was not stabile. The inhibition zones of the mixture of pszh9944 and HY96-2 are not bigger than pszh9944 or HY96-2, but according to the colonial morphology and the repeatability, the effect of the mixture were more stability. 2. Results of pot culture experiment of bactericides and their mixtures control to tobacco bacterial wiltThe results of pot culture experiment showed that the control effect of Thiodiazole-copper were just so so, Jinggangmycin had no control effect. Jinggangmycin mixed with Agrostreptomycin had synergism for the control. But Thiodiazole-copper mixed with Agrostreptomycin had no synergism. Biologic agent pszh9944^ HY96-2 have some control effect on tobacco bacterial wilt, but the effect was not stabile, and the effect was easily influenced by environmental conditions, the mixture of pszh9944 and HY96-2 had on control effect increased.. Through plate culture experiment, it was discussed that the influencing factors of application technology effecting on HY96-2 to tobacco bacterial wilt. The result indicated that holes application technology and root dipping application technology had better effects than pouring application technology during transplant. After 20 days of bacteria application, the effect of hole application technology was 35.44%, the effect of root dipping application technology was 34.98%, and the effect of pouring application technology was 25.23%.3. Comparison of control effects of different bactericides to tobacco bacterial wilt in fieldAccording to comparing of control effects of different bactericides to tobacco bacterial wilt on field, the result indicated that two mixtures includingâ… andâ…¡all had synergism for tobacco bacterial wilt control, and the mixtureâ…¡had better effect than mixtureâ… . pszh9944 and HY96-2 had some effects to tobacco bacterial wilt, but no boosting to the growth of tobacco. mixtureâ… , mixtureâ…¡, Agro-streptomycin, pszh9944 and HY96-2 were studied on applied technology in field. The result showed same effect that holes application technology had better effect than pouring application technology during transplant, and the key technology of control to tobacco bacterial wilt was protection of root avoiding intrusion by Ralatonia solanacearum during transplant.4. Study on some fators of influence the effect of HY96-2 and the occurring of tobacco bacterial wiltIt was discussed that the influencing factors of pH and the application technique to control effect of HY96-2, and the results showed: (1) When the pH=5.5-8.0, the growth of HY96-2 were normal in the experiment of plate culture, but in the conditions of peracid and peralkali, the growth of HY96-2 were restrained. (2) the control effect of HY96-2 were best when soil pH is about 6.0 in the experiment of pot culture.According to the investigation of tobacco bacterial wilt occurring and developing related with pH value, content of water-solubility Ca of soil in field, there was serious disease of tobacco bacterial wilt in acid soil field, and no relation was found between content of water-solubility Ca and the disease. Moreover, the disease strictly restrained by climate, the disease manifested symptom when climate condition was high temperature and high humidity, and tobacco bacterial wilt fastigium was occurred under durative high temperature and humidity climate.5. Key controlling technology of tobacco bacterial wiltThrough study on screening for bactericides to tobacco bacterial wilt control, influnce factors and application technology, a suit of application technique of the bactericid control tobacco bacterial wilt were got, the outlines as follows: in the area which tobacco bacterial wilt occurred badly and soil was meta acid, we should do some thing to adjust soil pH before tobacco transplanted. Useing biologic agent when tobacco in seeding stage, it could improve the colonization of biologic agent at plant root; At the same time, uesing biologic agent in soil in order to improve the microorganism diversity in soil.Useing chemical agent with the method of hole application during tobacco transplant in order to prevent pathogenic bacteria to infectting tobacco root. Through these technique scheme, bactericides could exert the best control effect, so the loss caused by tobacco bacterial wilt would reduce.
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