Citrus sandskin disease is a symptom of Citrus resinous disease. The pathogen of the disease is Ascomycetes, which is a kind of weak parasitic fungus. The original form of the disease is citrus stromatocystis and asexual form is citrus pseudostemspot. Generally speaking, 15-30 ℃ is the most suitable temperature for the development of the disease. Generally, the most common sanding black spot is the host's stress defense reaction: secreting gelatinous substances to envelop the pathogen, while the cells rupture and release volatile compounds to kill the pathogen, which limits the harm of the pathogen, and the infected tissues form protuberances and visible black spots.
Harmful symptoms
Generally, there are three kinds of harmful symptoms in different parts:
1、 Young fruits, shoots and young leaves are damaged (disease will not appear before the new branches are mature, so prevention should be done well in advance). Countless brown, dark brown scattered or dense pieces of microglial particles are produced on the surface of the diseased part, with rough surface, slightly uplifted, much like adhesion of many fine sands. Once the disease spots appear, there is no way to clear them with drugs.
2： In the branches of the disease, the common flow of gum type and dry type.
Flow gum type: when the branches are damaged, the cortex at the initial stage is soft, with small cracks and water stains, and exudes brown gum liquid, and has a similar smell of distiller's grains. Under the condition of high temperature and dryness, the diseased part gradually dried up and sank, the cortex cracked and peeled off, the xylem exposed and the scar raised around.
Dry and withered type: the cortex of the diseased branches is reddish brown, slightly sunken, slightly cracked, and does not peel off. There is an obvious uplifted line at the junction of the diseased and healthy shoots, but it can also be converted to flow gum type when the high humidity and temperature are appropriate. The pathogen can invade the xylem through the cortex, and the damaged part is light gray brown. There is a yellow brown or black brown mark at the junction of the disease and the healthy part.
3： The disease of fruit in storage period is also called Brown rot. It mainly occurs in mature fruit and mature fruit in storage period. The round or nearly round brown spots of water stains appear at the first place, then the spots expand to the navel, and the edge is wavy. The pathogen overwinters on the dead branches and trunks with mycelium, conidia and ascospores. After overwintering, a large number of conidia and conidia, ascospores and ascospores are produced, which are transmitted by wind and rain to induce infection.
Incidence regularity
Resin disease can occur all year round, and the harmful symptoms are irreversible. In the management process, agricultural control is the main, chemical control is the auxiliary. The strength of trees is closely related to the occurrence of resin disease, as well as soil health, weather conditions and so on. In Meishan, the local late maturing mixed orange sand skin disease showed an outbreak trend in 2018 due to the weather and the choice of medicine in the citrus price market. The sprouting of spring shoots is harmful to new shoots; after flowering, it begins to harm young fruits from April to mid May; from mid May to mid June, it mainly harms summer shoots and fruits; from July to August, leaves, branches and fruits are harmful; from September, it mainly harms autumn Qie and fruits. Other articles such as hazard symptoms and field management methods do not explain basic plant protection, please search Baidu by yourself. The main control periods of the disease are generally divided into six time points, corresponding to the citrus garden clearing period, spring germination period, flower 2 / 3, young fruit period, fruit expansion period and autumn germination period. The prevention and control time points are basically consensus, not too much elaboration, and the early prevention and control effect is better than the later prevention and control effect.
Route of transmission
The main pathogens are mycelium, conidia and conidia living through the winter in the diseased tree. When the environmental conditions are suitable, a large number of conidia are formed, and the overflowing conidia are transmitted by wind, rain, insects and other media.
Conditions of onset
Only when the water is wet can the spores germinate and infect. The suitable temperature for conidia formation, germination and infection was 15-25 ℃. The germ tube produced by spore germination can only invade the host's wound (frostbite, burn, cut wound, insect injury, etc.) to get deep inside. On the surface of the new tissues, such as the tender leaves and young fruits, which have no wound and have strong vitality, the infection of the pathogen is blocked in the epidermis of the host, forming many colloidal small black spots. Therefore, only when the host has a large number of wounds, and there is a lot of rain, and the temperature is appropriate, the trunk flow of gum and dry and fruit stalk rot will be popular. However, the occurrence of black spots and sand skins only needs more rain and suitable temperature. In the citrus producing areas with more rain, black spots and sand skins are popular all the year round.
References
In recent years, some references and views on the prevention and treatment of sand skin disease have been given.
In the twenty-ninth volume third issue of Zhejiang citrus, Chen Guoqing and other papers submitted by the author of 2012, "80% big M-45 to control citrus black spot", through two years of tests, 4 times a year, the results showed that rainfall had great influence on the incidence rate of sand skin disease, and had a great influence on the prevention and control of mancozeb. The rainfall in 2010 was large, and the average control effect was only 66.38, 2011 The annual rainfall is smaller than that in 2010, and the average control effect is 95.32. Through searching a large number of papers and field experiments, it was found that the control of sand skin disease by mancozeb could be significantly improved by increasing additives to improve the ability of rain erosion resistance.
2、 In the seventh issue of modern agricultural science and technology in 2014, the occurrence and control of citrus sandskin disease in Gongcheng County, the field test results of several chemicals against sandskin disease in Ping'an township of Gongcheng County in 2013 are summarized as follows:
medicament
disease index
Control effect
70% prosen zinc wettable powder 600 times
Seventy-three point six eight
3.47aA
60% pyrazolyl ester * 1000 fold
Seventy-two point eight five
4.56aA
25% azoxystrobin suspension 2000 times
Seventy-two point one three
5.50aA
80% mancozeb 600 times
Seventy-four point one six
2.84aA
CK
Seventy-six point three three
~ ~
The control effect of protective drugs after the pathogen enters the tree.
Occurrence and control of citrus sandskin disease in Gongcheng County (Deng Shishu, Chen Deyu, etc.)
Through this experiment, it is shown that the rain is dripping during the experiment period in Gongcheng County, and the application of the medicine needs to depend on the weather to seize the time. The experiment plan is to spray the same medicine once a month from March to June. From the summary table of test results, it can be seen that the control effect of each group of fungicides is very low. It can be judged that the application of fungicides once a month under very bad weather conditions is not enough to prevent and control sandskin disease. Therefore, in order to control sandskin disease, it is necessary to use fungicides at high frequency under severe and rainy weather. In addition, the experimental results show that the control effect can be improved with the participation of internal fungicides. In 2012, the field experiment of Gongcheng plant protection station showed that the control effect of Difenoconazole was 80.69% - 84.03%. The control effect was 73.18% higher than that of 80% mancozeb 600 times.
3、 In 2018, Hunan Agricultural University published a paper on Hunan agricultural science.
The virulence test results of 26 fungicides on the mycelial growth of citrus sandskin (the name of the manufacturer providing the fungicide will not be listed, and interested friends can find it by themselves)
Test bactericide EC50 (mg / L)
250G / L pyrazolyl EC
Zero point two zero zero one
50% pyrazolide WDG
Zero point two zero eight one
12% benzo · fluoroamide SC
Zero point two six nine nine
450g / L prochlorazine EW
Zero point three two six nine
70% thiophanate methyl WDG
Zero point five three six seven
42.8% fipronil · oxime SC
Zero point six one seven four
22% imazalole EW
Zero point six eight seven nine
75% manganese zinc WP
Zero point eight Zero Zero Five
17% zolyl ether · epoxiconazole SC
Zero point eight one three one
10% hexazol SC
Zero point eight seven six nine
18% copper oleate EC
Zero point nine two six three
27.8% thiofuran · hexazol SC
One point one five six nine
75% chlorothalonil WDG
One point two zero four six
4% tetrafluoroetherazole EW
One point three zero seven two
50% Benazolin WP
One point four nine eight zero
60% MnZn · NbZ WP
Two point zero nine four six
65% zinc WP
Two point six six seven one
16% prochloraz · isocarbazide SC
Two point eight eight two seven
430g / L tebuconazole SC
Three point two four three eight
80% mancozeb WP
Three point three nine four six
20% enoxime tebuconazole SC
Three point four one seven nine
40% clove tebuconazole SC
Three point seven five six five
325g / L benzoxystrobin SC
Five point one five zero nine
50% Pyridylamine WDG
Nine point zero one one two
80% captan WDG
Nine point four two two one
70% pronozeb WP
Sixteen point one eight one nine
4、 The data of this paper are also found for pyrazol + manganese replacement in the market.
The results of virulence test of the mixture of pyrazolyl ester and mancozeb.
In this experiment, pyrazolyl ether ester TC and mancozeb TC were compounded. The results showed that pyrazolyl ether ester TC and mancozeb TC showed synergistic effect at different mass ratio, and the synergistic effect of 1:5 was the most obvious, and the synergistic coefficient (SR) was 7.6295. The results showed that the synergistic effect of the two combinations was very good, which had the potential of development and could be used as a reference for the control of citrus sandskin disease in agriculture.
5、 In 2017, Hunan Agricultural University published a paper on China fruit tree.
The results of laboratory toxicity test of five fungicides to the pathogens of citrus sandskin disease
The results showed that 25% prochloraz had the highest virulence to the pathogen of citrus sandskin disease, the EC50 value was 0.099 μ g / ml, and the order of bacteriostatic effect of fungicide was prochloraz > Difenoconazole > carbendazim > ethyl aluminum · manganese zinc > mancozeb.
6、 The indoor toxicity of 33 fungicides to sandskin pathogen
The virulence of 33 fungicides to sand skin pathogen
Drug name
Median lethal dose
Whether there is internal absorption
Bactericidal mechanism
Reference validity period (days)
Biguanidine trioctylbenzene sulfonate
Zero point zero one one two
nothing
Infiltrate cytoplasma
No data
Fluosilazole
Zero point zero four six two
good
Influence sterol synthesis
20-25
Carbendazim
Zero point zero five six three
good
Interfere with the formation of microtubules in bacteria
7~10
prochloraz-manganese chloride complex
Zero point three seven nine three
nothing
Demethylation
7~10
Pyrazolyl ester
Zero point six three nine two
good
Inhibition of energy synthesis
10-20
Oximex · tebuconazole
Zero point six nine seven nine
good
Influence sterol synthesis
20-25
Pyrazolyl ester
Zero point seven one five six
Some of the ingredients are absorbable
Multiple roles
7-20
Difenoconazole
Zero point seven two seven three
good
Influence sterol synthesis
Twenty
prochloraz
Zero point eight six five two
difference
Demethylation
7~10
tebuconazole
Zero point nine two two two
good
Influence sterol synthesis
20-25
Thiophanate methyl
One point seven two nine six
good
Interfere with the formation of microtubules in bacteria
7~10
Propiconazole
Two point zero one one four
good
Influence sterol synthesis
20-25
Carbendazim * mancozeb
Three point zero six one
Some of the ingredients are absorbable
Multiple roles
Ten
Pythium
Three point two three four seven
good
Interference signal conversion
Seven
Myclobutanil
Three point two eight one six
good
Influence sterol synthesis
20-25
Imazalil
Five point three three six six
good
Demethylation
Fifteen
Quinoline copper
Ten point two two zero two
Yes
Coagulation cell wall
7~10
Enazole alcohol
Ten point six eight seven eight
good
Influence sterol synthesis
Twenty
Iprodione
Fourteen point one three three
good
Interference signal conversion
Six
propineb
Fourteen point nine four eight eight
nothing
Inhibition of pyruvate oxidation in bacteria
7~10
Sodium dichloroisobromocyanurate
Fifteen point one two seven three
Uncertain
Destroy cell wall
Three
azoxystrobin
Sixteen point four eight nine
good
Inhibition of energy synthesis
10-20
Jinggangmycin
Twenty-six point seven three four
good
Affect inositol synthesis
Seven
Zine
Sixty-six point six eight five
nothing
Inhibition of pyruvate oxidation in bacteria
7~10
Ether bacteria ester
Seventy-one point eight six
good
Inhibition of energy synthesis
No use value
Fenaminosulf
Two hundred and seventy-five point eight eight
commonly
Interference with coenzyme electron transfer
Copper sulfate basic
One thousand three hundred and seventy-eight point four three five
nothing
Coagulation cell wall
Clomithromycin
Two thousand one hundred and forty-nine point eight one nine
good
Affect protein synthesis
Bacillus subtilis
Two thousand seven hundred and eight point three three one
nothing
Microbial destruction of cell membrane
Morpholine
Three thousand three hundred and seventeen point seven six three
good
Destroy the formation of cell wall membrane
Chlorothalonil
Three thousand three hundred and thirty-three point nine five six
nothing
Destroy the activity of amino acid synthetase
Bacteriocin
Five thousand seven hundred and twenty point three eight eight
nothing
Cause protoplast agglutination in mycelium cells
Ye Ke Zhi
Nineteen thousand two hundred and nineteen point nine three seven
good
Interfering with amino acid metabolism of pathogenic bacteria
The indoor toxicity of 33 fungicides to sand skin pathogens (Zhou Na, et al.)
We can get a lot of information by reading the indoor toxicity table:
1. Triazole fungicides have a strong killing effect on the pathogen of sandskin disease. Flusilazole has the best activity, followed by Difenoconazole, and tebuconazole and Difenoconazole have the same median lethal dose. Triazole fungicides have the characteristics of high efficacy, moderate price and long duration, which are the main drugs for the prevention and treatment of skin diseases. thank