Studies On Key-Factor Analysis Of Tobacco Wildfire Disease’s Occurrence And Its Control Techniques

Tobacco wildfire disease caused by Pseudomonas syringae pv. tabaci, one of the primary tobacco bacterial diseases, which has explosivity and destructivity when surrounding environment is conformable for it to be reproduced and epidemic on tobacco leaves. This disease ususlly creats tremendous loss of tobacco production when it happens in the main tobacco planting areas all over China, especially in the high altitude areas. It has been still not perfect for the system of controlling to wildfire disease, so far. In Forecasting and warning, many studies showed that, there are no systemic studies and no uniform results on searching for key factors deciding wildfire disease to happen or not. In controlling, take it for granted that singal or several common bactericides can’t control wildfire disease fundamentally, but chemical control is sill the main way, and the number of studies on improving antiviral ability of tobacco to against wildfire disease is very small. In order to solve the problems mentioned above, people employed in the job of tobacco plant protection should adhere to the principles that take "forecasting and early warning" as security, take "tobacco health measures to improve tobacco ability to against plant disease" as a core, take "chemical control" as an important method, and under the guidance of plant medicine theory and "health-warning-comprehensive regulation" new plant protection concept, take "sample collection and measurement, field plot test, data collection and analysis" as main methods, carried out systemic studies on wildfire disease step by step, mainly including:the relationship between happens of wildfire disease and related factors such as climate factor and nutritional factor, control technique of wildfire disease by spraying plant growth regulation substance, control technique of wildfire disease by spraying induced resistance material, control technique of Wildfire Disease by spraying mineral nutrition elements, and control technique of wildfire disease by spraying chemical pesticides. Finally,"health-warming-comprehensive regulation" prevention and control system of tobacco wildfire disease was preliminary formed.1. Analysis of key factors deciding wildfire disease occurence(1) By making integrated analysis between meteorological datas and the surveys of disease index, we can see that there will be different key factors influencing tobacco wildfire disease index in different tobacco growth stage and pathogen infestation stage. The results showed that:Initial stage of wildfire disease infection, there was a significant correlation with low-temperature phase, but no obvious relation with daily rainfall, leaf wetness and sunshine hours; after the pathogen successfully infecting and showing symptoms, prevalence speed of wildfire disease had positive correlation with daily average temperature, daily rainfall and leaf wetness, had negative correlation with daily sunshine hours; later stage of tobacco growth, little rainfall, more sunshine, low temperature and dry weather, all could inhibit wildfire disease in some extent.(2) Make comparative analysis of the samples from tobacco wildfire disease fields and no disease fields with the methods of "factor analysis" and "frequency analysis". The results showed that:high containing levels of Mn and Mg in the soils were seen as the key factors influencing tobacco wildfire disease occurrence.2. The functions of plant growth regulators to inhibit tobacco wildfire diseaseSome plant growth regulators were sprayed on tobacco leaves about10days after the tobacco were transplanted in the fields, some positive function in inhibiting wildfire disease had been found, at the same time, which also can effect the tobacco agricultrue characters. The results showed that salicylic acid treatment had the smallest disease leaves ratio in each investigation, and in disease index, salicylic acid treatment also had the minimum value; in the control effects after last treatment,7regulators all have certain effects to inhibit wildfire disease, but the salicylic acid treatment has the best effect, which could reach to71.95%; contrast with xalic acid treatment, vitality element treatment, GA treatment, no significant difference (P<0.05). In addition, salicylic acid has no negative effect in agronomic characters.3. The functions of plant induced resistant materials to inhibit tobacco wildfire diseaseIt is about20days after tobacco were transplanted in fields while tobacco plants begin to adapt to the field environment. at this time,5kinds of plant resistance induction materials were choosed to spay on tobacco leaves to study their functions to inhibit tobacco wildfiredisease. The results showed that:every treatment had positive effects in inhibiting tobacco wildfire disease, Tian da2116and Bestrong had the better effects than other treatment were76.05%and87.01%, which were adjacent to88.37%of contrast treatment the gum rosin acid copper; but no significant difference (P<0.05).. In addition, bestrong also can improve tobacco leaves early sprouting; contrast with blanktreatment, tian da2116and bestrong both can increase tobacco plant stem girth; about the leaf area, two kinds of material also has the positive role.4. The function of medium and trace elements to inhibit tobacco wildfire diseaseThere are direct or indirect influence of trace mineral elements on infection of plant pathogen, propagation of plant pathogen, susceptibility and resistance of host plant, in general, plants need a perfect nutrition situation, which is important for the plant to have a good growth and high resistance ability. It is about30days after tobacco were transplanted in fields while8kinds of medium and trace elements were choosed to spay on tobacco leaves to study their functions to inhibit tobacco wildfiredisease. Results showed that:In rosette stage of tobacco, there were better control effects by spraying boric acid and copper sulfate, after last treated, the effects were respectively60.14%and54.84%, but no significant difference in8kinds of element. More over, two kinds of reagents not only had no negative effects on tobacco growth, such as the positive effects of boric acid in improving tobacco tallness and maximal tobacco leaf area. In addition, spraying Magnesium sulfate on tobacco leaves could amplify wildfire disease index.5. The combined action of chemicals to control tobacco wildfire disease In the tobacco field growth period, selecting several new pesticide be popular in market to carry out the experiment, with the methods of analyzing the rate of disease leaves, disease index and the speed to inhibit wildfire disease index, finally, the combined actions plan of several pesticids to control early stage tobacco wildfire disease by three times were determined:The first treatment, thiodiazole copper1000times liquid; the second treatment, normycin+energy gold+de Kopp (3:3:1)1000times liquid; the third treatment, thiodiazole copper1000times fluid;10days interval among every treatment. With the same method, the combined actions plan of several pesticids to control tobacco picking stage wildfire disease by three times were determined:first treatment, thiediazole copper+dimethachlon (1:1)600times liquid, the second treatment, thiodiazole copper600times liquid; the third treatment, normycin600times fluid;7-10days interval among every treatment.