Citrus smut is a type of citrus resin disease. Depending on the location and period of occurrence, the resin disease includes the disease of the upper part of the disease, and the rot of the fruit during the storage period. Shapi disease can be infected for the anniversary, and we can't soak the fruit trees in the syrup every day. Therefore, it is impossible to effectively prevent and control the smut disease. It is impossible to adhere to the guidelines of agriculture and chemical control.
Reduce the number of pathogens: managers must first work to reduce the number of pathogens, isolate contact between pathogens and trees, and reduce the chance of infection.
1. Seedlings should be carefully disinfected before being introduced into the orchard. It is best to use detoxified seedlings.
2. Do a good job of drainage facilities, reduce the humidity of the orchard, carefully trim, ensure ventilation and light, sunlight is the cheapest fungicide.
3. Spread the appropriate amount of quicklime throughout the garden with the pH (soil pH) permit.
4. Carefully clear the garden: burnt or deep-buried litter, late-ripe citrus varieties should pay attention to the use of fungicide protection.
5. Actively control pests and diseases, build windbreaks, adopt membranes and freeze prevention, etc. to reduce the chance of tree injury.
6. Develop the habit of using a fungicide before strong winds and heavy rain.
7. Pick up the stem resin disease strain.
8. Before the spring buds in February, choose the whole machine to spray the stone sulphur mixture + Nissolang (a red spider drug that can be mixed) and apply white trunk.
Cultivate robust trees and enhance stress resistance: Shapiosis is a weak parasitic bacterium, and a robust tree is beneficial for the prevention and control of smut disease. The methods for cultivating robust trees are:
1. Buried organic fertilizer, increased application of bacteria to improve soil, increase organic matter input to promote strong root system
2. Add calcium, magnesium and phosphate fertilizers, spray foliar fertilizer, pay attention to the application of calcium, magnesium, boron, zinc, iron, manganese and molybdenum fertilizers to avoid leaf deficiency and weakening yellowing.
3. Reasonable trimming, avoiding excessive load, timely harvesting, etc.
In short: if there is no pathogen, we don't have to worry about sand sickness; if there are few pathogens, there are few healthy wounds in the tree, we can control it; if the pathogen is large and the tree is weak and full, it will be really difficult.
In recent years, the occurrence of citrus smut is more common. After the leaves and fruits are damaged, sand-like pockmarks are formed on the surface, which seriously affects photosynthesis and fruit appearance. Once it occurs, it can prevent and treat suffering. The wholesale price of sick fruit is low, which seriously affects the benefits of growing farmers.
More serious citrus smut disease source: Huang Xiong
Illustration of the symptoms
The smut disease mainly harms the tip shoots, leaves and young fruits of citrus. The affected surface is scattered with many yellow-brown or dark-brown granules, which are densely integrated and feel rough and uneven.
In the early stage of the disease, a small needle-like spot that produces transparent greening
After the condition is aggravated, a brown or dark brown hard grainlet is formed.
The pathogen infects the immature fruit, and the incidence is similar to that of the shoots and leaves. The surface of the diseased part forms brown or black spots, lines, curves, rings or amorphous hard spots.
When the concentration of the bacteria is high, the condition is muddy or tear-like.
Epidemic characteristics
In December 2016, at Guilin Yuantou Farm
Popular route
â— There are three pathogens of citrus smut disease, all of which are weak parasitic bacteria. The pathogens are overwintered on mycelium and conidia in diseased tissues such as dead branches, dead bark, diseased branches, and leaves.
◠The next spring temperature is 15~30°C. When it is raining and damp, the overwintering bacteria begin to multiply and spread to new shoots, young leaves and young fruits by means of wind, rain and dew.
Epidemic law
Citrus smut disease can occur throughout the year, and summer and autumn rains are mostly the peak period. The freezing of citrus in winter and spring is also the main cause of smut disease.
Spring shoot period: endangering new shoots, leaves
Xiehua period: harming young fruit
Summer season: endangering summer shoots and fruits
Fruit development period: leaves, shoots, fruits
Autumn shoot period: harming new shoots and fruits
Popular cause
â— Improper fertilization, poor soil permeability, poor tree potential, and susceptible to illness.
â— The management is extensive, the citrus orchard is too dense or not trimmed in time, resulting in poor ventilation and light transmission conditions in the citrus grove.
â— Poor drainage, easy to cause tree recession, reduced tree resistance, susceptible to disease.
Misunderstanding about dermatosis
Weak parasitic disease
The pathogen of citrus smut is characterized by a citrus bacterium, and the asexual state is a citrus stalk, which is a weak parasite.
A weak parasitic disease is a disease caused by infection of a plant by a fungus or bacteria that is less parasitic. The occurrence of such diseases is often related to the environmental stress of plants, and once they occur, they are often characterized by widespread occurrence, serious damage, and difficulty in prevention and control.
No matter what kind of environmental stress, such as high temperature, freezing damage, drought and flood, or other pests and diseases, it will affect the tree to varying degrees, giving the sand skin disease a chance.
Therefore, it is particularly important to prevent smut disease, strengthen cultivation management, and stabilize the tree.
What is the black spot of smut disease?
Since the pathogen of smut is a weak parasitic fungus, after the invasion of the pathogen, it is quickly subjected to the host's defense reaction: the secretion of the gelatinous substance surrounds the pathogen, and the oil cell ruptures and releases volatile compounds to kill the pathogen, causing the expansion of the pathogen to be restricted. The infected tissue forms a black spot with protrusions and visible to the naked eye.
Simply put, the black spot of citrus smut is the product of the host defense response, and once the germ is infected, black spots will occur. But what is fatal is that there is no way to eliminate the small black spots, which has a great impact on the fruit commodity rate.
Therefore, the focus of prevention and control of smut disease must be on preventing infection of pathogens.
Integrated prevention method
The prevention and control of citrus smut is a systematic project, which must be combined with field cultivation management and chemical control for comprehensive prevention and control.
1. Strengthen field management
Perform reasonable pruning to ensure the stability of the tree and coordinate the relationship between results and growth;
In the rainy season, drainage work should be done in time to prevent pests and diseases in time to avoid mechanical wounds and pests;
Add organic fertilizer, bio-organic fertilizer, and use sea snail bio-stimulant (leaf root type) to balance soil nutrition, enhance tree potential and resistance to disease and stress.
2, remove pathogens
Whitening the trunk of citrus in winter can not only effectively prevent citrus trees from being damaged by freezing, but also eliminate the bacteria and pests that overwinter on the trunk.
In the winter, the clearing garden is disinfected, and the gang of hard rubber and the rotted cortex and wood layer of the lower part are scraped off, and they are concentrated and buried or burned. Before the spring shoots sprout, the sulphur sulphur mixture is sterilized to remove the dead branches in the orchard. The leaves are concentrated and burned outside the orchard to reduce the pathogen.
3, chemical control
According to the incidence law of smut disease, in the Qingyuan period, spring bud germination, Xiehua 2/3, young fruit period, fruit expansion period, autumn shoot germination period to grasp the timing of application.
The first medication, the clearance period:
15% stupid ether carbazole · 15% propiconazole 3000 times. Winter pathogens have weak vitality, and the use of strong systemic and highly active fungicides can greatly reduce the number of pathogenic bacteria.
The second dose, spring germination (1 cm):
48% difenoconazole azoxystrobin 4000 times or 30% ether oxalate wettable powder + 80% mancozeb wettable powder 600 times. When the spring shoots sprout 1 cm, you should fight the medicine. Eliminate smut bacteria and prevent infestation of spring shoots; add organic carbon + trace element foliar fertilizer to promote the spring shoots to turn green, mature, strong, and the bacteria are not easy to infect.
The third medication, Xie Hua 2/3:
48% difenoconazole azoxystrobin 4000 times or 30% ether oxalate wettable powder + 80% mancozeb wettable powder 600 times or polypropylene zinc 600 times. Effectively eliminate young smut and promote the development of young fruit.
The fourth medication, young fruit period:
40% pyraclostrobin · tebuconazole + 80% mancozeb 600 times or propyl zinc 600 times. There are many rains in the young fruit period, and the use of long-acting and long-lasting agents can effectively prevent smut infection.
The fifth time, the fruit expansion period:
32% difenoconazole azoxystrobin suspension 3000 times. When the fruit is inflated, the cortex is fragile. During this period, the temperature is high and rainy, and the smut disease is easy to fruit. It is a key period for prevention and control throughout the year. The drug has strong systemic absorption, high activity and long-lasting effect, which can effectively eliminate germs.
The sixth medication, the autumn shoot germination period (1 cm):
32% difenoconazole azoxystrobin suspension 4000 times +80% mancozeb 600 times or 60% pyraclostrobin. Autumn is the main result of the coming year, protecting the autumn to prevent smut disease from infesting young leaves, and it is crucial to cultivate a healthy autumn.
Shapiosis drug prevention
Drug testing The majority of scientific research workers have carried out many useful experiments and explorations on the prevention and treatment of smut disease.
Table 1: The protective effects of several protective agents on the skin disease after entering the tree in Pingxiang County, Gongcheng County
Data source: The occurrence and prevention of citrus smut in Gongcheng County (Gongcheng Plant Protection Station, Gongcheng Pingxiang Township Fruit Service Station Deng Shishu, Chen Dejun, etc.)
Rainwater dripping during the Gongcheng test, the test plan: spray the same drug every month from March to June. From the summary of test results, it can be seen that the control effect of each group of pesticides is very low, and it can be judged that in the next month, the bactericide is not enough to prevent and treat smut disease, and the control of smut disease needs to be higher in the harsh and rainy weather. Frequent use of fungicides. In addition, from the test results: with the involvement of systemic fungicides, the control effect can be improved.
Indoor virulence of 33 fungicides against smut
The virulence data comes from: "The indoor virulence of 33 fungicides against S. sinensis" (Southwest University, National Citrus Technology Engineering Technology Center Zhou Na, Hu Junhua, etc.)
After reading this form we can get a lot of information:
1. The triazole fungicide has a strong killing effect on the disease caused by smut, and the activity of flusilazole is the best, followed by difenoconazole, and the lethal dose of tebuconazole and difenoconazole is close. These three triazole fungicides are available.
2. Although the benzimidazole fungicide is an old drug, the effects of carbendazim and thiophanate-methyl on the pathogen of the skin disease are still outstanding.
3. The methoxy acrylate fungicide can be used, the difference between the lethal dose is too large, and the available concentration of pyraclostrobin is less than 25 times lower than the azoxystrobin. It is recommended to use pyraclostrobin on citrus.
4. The effect of the dicarboximide fungicide is good, and the preferred agent is procymidone. It can be arranged in the middle and late September to treat the brown rot of the plague.
5. Quinoline copper in copper preparations works well, citrus varieties with ulcer disease are preferred, and basic copper sulphate cannot be used.
6. In the absence of systemic protective drugs, imidazole fungicides are preferred as prochloraz and manganese salts. Dithiocarbamate fungicides are recommended for zinc and zinc, and can also be used with Daisen. The chlorothalonil has a poor pathogenic effect on the skin disease, and the smear area is recommended to abandon the use of this drug.
7. The pathogen is very sensitive to Baco (bisindole trioctylbenzene sulfonate), which may be related to the fact that this drug has not been used. This medicine is too expensive and difficult to compound. You can test it first to see if it is applied. value.
8. There are still many varieties of fungicides that do not appear in the test list. Research institutes can continue to conduct experiments to provide a theoretical basis for field operations.
Shapiosis drug selection:
1. Triazole fungicides are characterized by high therapeutic efficiency, medium price and long-lasting effect. They are the main drugs for the prevention and treatment of saporosis. It is a good time to use triazole fungicides when 3/4 of Xiehua, after fruit picking, when observing the disease of Shapi disease, and during the rainy season.
This kind of fungicide has a certain inhibitory effect. The inhibitory effect of difenoconazole on young fruit is relatively light. It can be used in the first half of the year, with flusilazole or propiconazole in the second half of the year, or they can be compounded. The risk of triazole fungicide resistance is moderate, and the number of uses per year should not exceed four. It can be used twice in the treatment. It is best to use it at other intervals.
2. The methoxy acrylate fungicide has the advantages of wide bactericidal spectrum, strong trees and rain-resistant scouring, which can strongly inhibit the germination of pathogenic spores, but the effect of spore germination will be greatly reduced, and there is no episode in the disease. Used when.
The point of action of this type of fungicide is easy to resist, and it is best to use a compounding agent, which should not be used more than three times a year, and must be used at intervals. When the temperature is lower than 15 degrees, compounding the emulsion pesticide, and compounding the organophosphorus pesticide, there may be phytotoxicity. When the color conversion period is used, it is possible to delay the color change. These characteristics must be noted when selecting. It is a suitable time for rainy seasons and when no signs of disease are observed.
3. Precautions for medication for different citrus varieties.
3.1 Because the benzimidazole fungicides are inefficient against Alternaria, the citrus varieties of Alternaria alternata brown spot disease such as red orange, tribute orange, Maogu citrus and Ehime 28 are not suitable for carbendazim alone. Tobuzin is used to prevent and control sapyosis. It can be selected from Table 2 to use a systemic fungicide and a dithiocarbamate fungicide.
3.2 citrus varieties with high-sensitivity ulcer disease, such as orange, pomelo, and citrus, to prevent and control the skin disease, to suppress the pathogen in the body before the occurrence of ulcer disease, and to protect the tree after the occurrence of ulcer disease, the copper preparation is responsible for Only when the copper preparation is found to be insufficient to control the fungal disease, the triazole fungicide, thiazolone, bromoxynil, and procymidone are used for supplementation. Among the dithiocarbamate fungicides, those having a high zinc content have an inhibitory effect on ulcerative bacteria and can be used.
Varieties and climates vary from place to place, and the symptoms of orchards vary widely. Management habits and drug supply are not the same. Managers can adjust according to their actual conditions.
At present, the scale of domestic agricultural production is small, and the sources of crops in the same region are complex. The rule of the unified defense is currently difficult to achieve, let alone the creation of disease-free areas. Therefore, the domestic pesticide use dose is much larger than that of developed countries. After citrus infection with saporosis, it takes a lot of work to control the cost. But if you don’t do this, you may fall into the vicious circle of “low quality – low price – no money to invest – low qualityâ€.
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