Preparation And Application Of Tetramycin·Tebuconazole Paint

Kiwifruit bacterial canker is a bacterial disease caused by Pseudomonas syringae pv.actinidiae.In recent years,kiwifruit bacterial canker has become one of the most important diseases during kiwifruit production in the word,which also causes significant economic losses for the kiwifruit industry in Guizhou province.At present,no specific inhibitors of kiwifruit bacterial canker are available in the production of kiwifruit.The most frequently used method to control this disease is spraying bactericides such as copper hydroxide and quinoline copper.However,long-term use of these bactericides may lead to drug resistance,decreasing effectiveness of pesticides.In addition,bactericide spraying is not capable to protect large wounds from infection.As the most suitable dosage form for wound protection,paint is a new development direction for the prevention and control of stem diseases in agricultural production.In this study,synergistic agent combination and paint formulation were screened for the control of kiwifruit bacterial canker.The physicochemical properties of the paint were tested;its bioactivities were investigated;and its application effects were evaluated,so as to explore new ideas for the prevention and treatment of kiwifruit bacterial canker.The main research results are as follows:1.The synergistic agent combination was determined to control kiwifruit bacterial canker.The filter paper method was used to determine the virulence of different agents to kiwifruit bacterial canker pathogen,and five single agents with varying antibacterial activities were selected,including tetrasamycin,ethyl allicin,ambam,copper hydroxide,and tebuconazole.According to the principle of agent combination,four agents（tetramycin,ethyl allicin,ambam and tebuconazole）were combined in pairs.The results showed that the most effective combination was tetrasamycin and tebuconazole,with a ratio of active ingredient weight of 2:1（tetrasamycin·tebuconazole）,which had the lowest EC₅₀ value of 5.43μg/m L.Therefore,tetrasamycin·tebuconazole（2:1）were determined to be the antibacterial active ingredients of the paint.2.The adjuvant formulation and preparation process of tetramycin·tebuconazole paint were finalized.The film forming substances were screened according to the solubilizing property,preparation state,viscosity value,tree body attachment rate,film forming property and other indexes.It was determined that 2%xanthan gum and 0.5%CMC-Na combination were film forming substances,and the filler,water proofing agent,antifreeze agent and defoaming agent were added for formulation optimization.Finally,the film forming components were determined,which included 2%xanthan gum,0.5%CMC-Na,1%Si O₂,1%phenylpropanoid emulsion,2%ethylene glycol,and 2%silicone.The influences of adjuvant components and their concentrations on the antibacterial activity of tetrasamycin·tebuconazole were tested by using filter paper method.Based on the initial screening results,it was determined that the solubilizer was 0.2%tween 80;the antibacterial synergist was 0.15%s citric acid;and the penetrant was 0.3%trisiloxane.With adjuvant concentration as the independent variable and the bioactivity of tetrasamycin·tebuconazole as the response value,Box-Behnken response surface was used to optimize and verify the adjuvant composition,which was finalized as 0.19%tween 80,0.16%citric acid and 0.35%trisiloxane.Through the film forming process,tetramycin·tebuconazole,film-forming components and adjuvants were mixed to prepare paints containing serial concentrations（0.000625%-0.1%）of active ingredients.3.The physicochemical properties and biological activities of tetramycin·tebuconazole paint were determined.The appearance,film-forming ability and film-forming time of tetramycin·tebuconazole paint were measured,and it was found that it was thick,non-precipitating,milky white to yellowish brown mucus with high viscosity and weak acidity.The extension area of 0.5g paint in the Petri dish reached 1815.23 mm².The adhesion rate of the tree body reached 99.26%,the contact angle was 18.37°.After 243 minutes of application,a tough film without bubbles can be formed,which had strong resistance to rain-wash.The indoor bioactivity test showed that the EC₅₀ of the paint against kiwifruit bacterial canker was 0.117μg/m L,which was 45.4 times lower than that of active compound combination(EC₅₀=5.43μg/m L).The changes of EC₅₀ value were monitored regularly,and the period of validity was 180-210 days,which suggested a strong long-term storage stability.By the experiments conducted on isolated branches,it was found that the protective effect of the paint was better than the therapeutic effect,and it is recommended to apply it before the infection of the pathogen.4.In order to clarify the application value of tetramycin·tebuconazole paint,the control efficacy on kiwifruit canker and safety on kiwifruit of the paint were evaluated.The field experiments showed that when the concentration of active ingredients reached 0.0025%or above,the paint displayed best control efficacy against kiwifruit bacterial canker.The control efficacies were not significantly different among the concentrations of 0.0025%and above,so the recommended concentration was 0.0025%.The safety of the paint at 1-8 times of the recommended concentration was evaluated.It was found that the application of the paint had a high safety,and the cost accounting indicated that it was cost-effective.In conclusion,tetramycin·tebuconazole paint has potential for development and can be applied in the field.