Causes and Control methods of bacterial Corner spot in Plant Diseases

According to Huaping County Organic late-ripening Mango Research Center, the temperature in Huaping this year is different from previous years. It is high and sometimes low in the early stage (February-April); from May to mid-June, the temperature is higher and the explosion is serious; bacterial angular spot disease occurred seriously in some mango planting areas. The fruit growers still couldn't control the medication over and over again.

Bacterial angular spot mainly harms leaves and melon strips. The leaves were damaged and became light brown after being waterlogged light green, which was polygonal due to the limitation of leaf veins. In the later stage, the lesion was grayish white and easy to perforate. When the humidity is high, white mucus is produced on the disease spot. The disease spot on the stem and melon strips is water-stained at first, nearly round, and then light gray. Cracks often occur in the middle of the disease spot, and bacterial pus is produced when it is wet. The fruit is rotten in the later stage and has a bad smell.

First, why is the corner spot of mango so difficult to treat?

To sum up, there are the following: 1. Most vegetarian fruit growers pay more attention to treatment than prevention. Most fruit growers take medication measures for the control of mango diseases and insect pests, which are often used to control bacterial diseases.

Organic copper fungicides, inorganic copper fungicides, agricultural antibiotics, thiazoles and microbial preparations were sprayed on leaves of fruit trees or fruits. Because the disease-causing bacteria are lurking in the tree and come out from the inside to the outside, spraying chemicals can only cure the surface, but the pathogenic bacteria in the tree are not killed, so they relapse in the event of the right weather. This medicament control method can only cure the symptoms. The plaque dries after 1-2 days and seems to be well, but when it comes to rainy or humid weather, the plaque begins to discharge bacterial pus again. This kind of temporary cure cannot cure the root cause of the disease, and it needs to be sprayed repeatedly, which is time-consuming, laborious and costly, and the effect is not obvious.

2. The consciousness of prevention and protection is poor. In the process of production, some fruit growers throw diseased branches and leaves and diseased fruits at will. Year after year, the orchard disease accumulates too much, and it is difficult to prevent and control once the outbreak occurs.

3. Angular spot disease can be transmitted by air. The disease prevention of fruit farmers is generally a single prevention and treatment, and it is difficult to combine prevention and treatment. On the other hand, most of the planting areas are connected, and the orchards are connected to each other. Once they encounter adverse weather, the disease will be a large area.

4. The use of medicine is not scientific. Many fruit growers do not have enough knowledge about the use of drugs, which often cause drug damage, and drug damage will also cause a large number of corner spot outbreaks.

Second, how to scientifically control bacterial corner spot of mango?

First of all, we must know the occurrence law of bacterial angular spot, understand the pathogenic factors, take corresponding effective control measures, give priority to prevention, comprehensive control, in order to control the disease in the bud and get twice the result with half the effort. Bacterial angular spot, also known as bacterial black spot or canker, is a frequent and important disease of mango. Often cause a large number of leaf spots and fruit spots, seriously affect the growth of fruit trees, fruit appearance and commercial value. Anthracnose and stalk rot fungi often invade fruits from diseased spots, causing a large number of rotten fruits during storage.

Symptoms: corner spot mainly harms mango leaves, branches, flower buds, flowers and fruits

On the leaves, water-stained dots are produced at first, and gradually expand into dark brown. The edges of enlarged disease spots are often polygonal due to the limitation of leaf veins. Sometimes multiple disease spots merge into larger disease spots, the surface of the disease spot is slightly raised, and there is often yellow halo around it. Leaf midrib and petiole can also be injured and split longitudinally. On the branches, the disease spot is dark brown ulcerated, when the disease spot expands and circles around the twig, it can cause the shoot to die. On the fruit, it shows water-stained dots at first, then expands into dark brown, the surface is raised, and the ulcer is cracked. The common symptoms of the disease department are: the disease spot is dark brown, the surface is raised, there is often yellow halo around the disease spot, and there is often an outflow of sticky juice from the disease tissue when the humidity is high. In addition, flower buds and leaf buds can be withered on highly susceptible varieties. The wound formed by the disease can also become the entrance of anthracnose and pedicle rot fungi, inducing a large number of fruit rot during storage.

(2) the law of incidence: angular spot is a bacterial disease. Diseased leaves, diseased branches, diseased fruits, diseased bodies, diseased seedlings and host weeds in or around the orchard are the initial infection sources of mango bacterial angular spot. Germs can spread through airflow, diseased seedlings, wind, Rain Water and so on. The pathogen invades from the wounds and water holes of leaves and fruits and causes the disease. The optimum temperature for the development of pathogens was 20-25 ℃. High temperature and heavy rain were beneficial to the occurrence of the disease. The disease was more serious in windy areas, windward areas or low-lying orchards, and lighter in orchards with shelter and high terrain. At present, there are some differences in the resistance of main mango varieties to bacterial angular spot, but there are no immune varieties.

(3) Prevention and control measures

1. Strengthen quarantine. Prevent pathogens from spreading with infected seedlings, scions and fruits.

two。 Take good disease prevention measures. ⑴ strengthen fertilizer and water management, improve soil environment, strengthen tree body: reasonably match organic fertilizer, biological bacterial fertilizer, medium and trace fertilizer, functional compound fertilizer, improve soil environment, enhance orchard soil aggregate structure formation, activate soil organic matter, increase beneficial bacteria, inhibit and kill harmful bacteria in soil, improve tree body reasonable nutrition supply, enhance tree potential, and improve tree resistance as a whole. ⑵ should do a good job in orchard hygiene. In the process of production, diseased leaves, branches and fruits should be cut off in time and burned or buried deeply. After fruit picking, the diseased remains of the orchard should be removed, the orchard should be cleared, and the source of infection should be reduced. ⑶ carries out tree shaping and pruning timely and appropriately to keep the crown and orchard ventilated and transparent and reduce the incidence of the disease. During the dry-wet period of ⑷, that is, before and after wind and rain, copper preparation or other bacterial agents should be sprayed in time for 1-2 times, and if ⑸ is in the fruit stage, it can be supplemented with pure organic calcium fertilizer twice in advance, combined with bacterial agents, which can effectively prevent the occurrence of angular spot.

3. Guard against the wind. If conditions permit, you can try to plant windbreaks around the orchard to reduce the attacks of strong winds and torrential rain.

4. Remedial measures after the occurrence of the disease. It is suggested that bacterial agents such as organic copper fungicides, inorganic copper fungicides, agricultural antibiotics, thiazoles and microbial preparations should be used alternately. Spray at least 2 times in a row, especially after wind and rain, it is best to use bacteria each time. Brief introduction of bacterial agents are as follows:

a. Organic copper fungicides: common organic copper preparations, including quinoline copper, thiomycete copper, ammonia copper, oleic acid copper, copper succinate, non-bacteria copper, thiosen copper and so on. This kind of fungicide has good control effect on some bacterial diseases. Quinoline copper and thiobacillus copper are widely used. The advantage of this kind of fungicide is safer, generally will not produce drug damage, flowering and young fruit stage can also be used; a wide range of use and time, fruit trees, rice, vegetables and so on can be applied; copper content is relatively low, will not cause the proliferation of mites, copper accumulation is small; good miscibility, convenient use, reduce the burden. The disadvantage of organic copper preparation is that the price is generally high.

b. Inorganic copper fungicides: common inorganic copper fungicides include: copper hydroxide, cuprous oxide, Bordeaux night, copper oxychloride. The advantages of this kind of fungicides are fast effect, low price and comparative advantage in cost. Its disadvantage is that it is easy to cause drug damage, and its use is prohibited or restricted in the flowering and young fruit stage; the miscibility is relatively poor, and the traditional copper preparation is mostly alkaline and cannot be mixed with other pesticides, so it needs to be used alone, which increases the labor cost. and it's easy to miss the best disease prevention and treatment period. Among them, the neutral (PH=7) inorganic copper preparation has better mixing.

c. Antibiotic fungicides: antibiotic fungicides, commonly used agricultural streptomycin, aureomycin, oxytetracycline hydrochloride, actinomycetone, etc., are the main varieties of antibiotics widely used at present. In order to use agricultural antibiotics, it is necessary to choose the appropriate method according to different plant diseases. For example, plant diseases transmitted by soil can be used as soil disinfectant; plant diseases transmitted by seeds and seedlings can be impregnated with antibiotics, such as seed soaking, root soaking, seedling soaking, or seedling bed spraying; for above-ground diseases of agricultural and forestry crops, plant spraying can be made at an appropriate time; used on fruit trees, it is mainly made into ointment to prevent bacterial ulcers. The advantage of this kind of fungicide is that the market is relatively popular, and the product can be sold without publicity; the effect of internal inhalation and treatment is better, but the disadvantage is that it has a long history of use and strong drug resistance.

d. Thiazoles: thiazoles, including leaf fumazol and thiazolyl zinc, were first used to control rice bacterial blight. In recent years, due to the expansion of the area of cash crops and the prevalence of bacterial diseases, these compounds have no bactericidal activity in vitro and are limited to the control of bacteria in soil. Homogenization competition is common, and it is a common product for the control of plant bacterial diseases. ⑸ microbial preparations: active microbial preparations, such as Bacillus polymyxus, Pseudomonas fluorescens, Bacillus subtilis and Bacillus subtilis, have become newly developed microbial preparations. This kind of biological pesticide is generally safe to the environment, can improve the soil, and can protect the health and safety of food, animals and plants and human beings, but the market acceptability of farmers is slightly poor.