Apple anthracnose, also known as bitter rot and late rot, is a disease on apples caused by the infection of Pleurotus.It mainly harms the fruit, and the near mature fruit is the most seriously affected, and it can also harm the fruit moss and branches.It mainly overwinters with mycelium in stiff fruit, fruit moss, diseased and withered branches, etc.[1]
Apple anthracnose occurs in all countries and regions in the world with warm and humid climate and suitable for apple planting.[2]Apple anthracnose is a common disease that mainly damages fruit in various apple producing areas in China.The disease is more serious in hot and rainy areas in summer, and the fruit rots after the disease. The disease rate reaches 30-60% in the epidemic year, which has a great impact on the quality and yield of apples.[3]
The control methods of apple anthracnose are mainly agricultural control and chemical control.First, strengthen management to improve disease resistance of fruit trees;Secondly, the disease source should be eradicated, and the fruits should be bagged at the same time;Finally, timely medication.[3]
The pathogen of apple anthracnose is in the form of small bush shell（Glomerella ciningulaia(Stonem.) Spauld. et Sch.），It belongs to Ascomycetes subphylum and Pleurolepis genus.The ascospore shell is produced on the hyphal layer or semi buried in the ovary. The shell wall has hairs, no lateral hyphae, and the ascospore is single celled and colorless.The asexual form is Colletotrichum gloeosporioides（Colletotrichum gloeosporioides(Penz.) Penz.et Sacc.），It belongs to the subgenus Hemiptera and the genus Anthrax.The conidial disc is buried under the host epidermis, pillow shaped, without bristles, and breaks through the epidermis after maturity.The conidiophores are arranged in parallel in a layer, cylindrical or upside down;Conidia are unicellular, colorless, long cylindrical or long printed net shaped.[4]
Physiological characteristics
The temperature of pathogen reproduction is 15-40 ℃, and the optimal temperature is 28 ℃;The suitable temperature for conidia formation is 25-28 ℃, and the relative humidity is above 80%;The optimum temperature for conidia germination is 28-32 ℃, and the relative temperature is above 95%. At this time, conidia can invade the pulp after contacting the fruit surface for 5 hours, and most of the bacteria will complete the invasion process after 10 hours.[3]
host
In addition to harming apples, the fungus can also infect many fruit trees such as crabapple, pear, grape, peach, walnut, hawthorn, persimmon, jujube, chestnut, citrus, litchi, hangguo, and black locust.[4]
Harmful symptoms
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Apple bitter rot
Apple anthracnose mainly damages the fruit;It also infringes on branches and fruit stands, but rarely.At the initial stage of the disease, the fruit presents large pale brown round spots with clear edges. The disease spots expand rapidly, resulting in soft rot (the pulp is slightly bitter, easy to distinguish from the good pulp), which is cone shaped and penetrates into the pulp.Later, the disease spots subsided, and the surface of the disease spots showed whorls of alternate colors.When the disease spot expands to 1-2 cm, protruding small particles emerge from the center of the disease spot. At first, they are brown, then black, arranged in concentric whorls, and gradually expand outward. This is the conidial of the pathogen.When the weather is wet, black particles break through the epidermis and overflow pink mucus, which is the conidium of the pathogen.One spot can extend to 1/3-1/2 of the fruit surface and rot to the core.There are one or more disease spots on the diseased fruit, which can rot the whole fruit and cause the fruit to fall off.If the fruit is infected in late autumn, the diseased fruit will rot, lose water, dry and shrink, and become black and stiff, which is obviously different from the good fruit.If the pathogen invades the fruit before harvest, the disease will continue to occur during storage.The disease of fruit stage mostly spreads from the top to the bottom, and when the damage is serious, the side shoots cannot be pulled out, and finally wither and die.The disease of branches and trunks mostly occurs at the base of diseased and insect branches, dead branches and weak growing branches. The disease symptoms are similar to those of fruits, and the surface of disease spots also produces black particles.Later, the diseased skin cracked and fell off, and the branches above the diseased part gradually withered and died in serious cases.[3]
Distribution range
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Apple anthrax occurs in all countries and regions in the world with warm and humid climate suitable for apple planting, such as China, the United States, Australia, the United Kingdom, France, Germany, Denmark, Bulgaria, the Netherlands, Russia, Brazil, Mexico, Japan, South Korea, etc.[2]
Infection cycle
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Apple anthracnose is an advanced fungal disease. The pathogen mainly overwinters on dead branches, damaged branches, dead fruit stands and diseased and stiff fruits with mycelium, and also on black locust.After apple blossoms fall in the second year, overwintering pathogens can produce a large number of spores under wet conditions, becoming the primary source of infection.Conidia are spread by wind, rain and insects, and invade from the pores, wounds or directly.The pathogen can infect the fruit from the young fruit stage to the fruit bearing stage, but the pathogen infected in the early stage is in the latent state due to the strong disease resistance of the young fruit, and cannot cause the disease of the fruit. The disease can only be caused when the disease resistance of the fruit decreases after the near maturity of the fruit. The disease has an obvious latent infection phenomenon.The pathogen spores (pink mucus) produced after the disease of near mature fruits can infect and damage the fruits again, and the disease has been repeatedly infected in the field.Especially under the high temperature and high humidity conditions in July and August, the bacteria multiply quickly and spread rapidly, that is, the more rain and the longer the rain time, the higher the incidence rate.The incidence of disease decreased when the temperature decreased in late autumn, but the susceptible fruits continued to suffer from disease.[3][5]
Epidemic law
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Morbid condition
one
Climate: The incubation period of bacteria is generally 3-13 days, and the maximum is 40-50 days.Under the conditions of high temperature, high humidity and much rain, anthrax germs reproduce quickly and spread rapidly, especially after rain, high temperature is more conducive to a pandemic;In late autumn, there is little rain and low temperature, and the disease is mild.The severity of the disease in different years is closely related to the early and late rainfall and the amount of rainfall in the same year. Generally, the disease is early and heavy in the year with early and more rainfall, and light in the dry year.[3]
two
Cultivation and management level: the disease is serious if the distance between plants and rows is small, the crown is large, the branches and leaves are dense, the ventilation and light transmission conditions are poor, the nitrogen fertilizer is applied preferentially, the soil is sticky, the terrain is low-lying, and the orchard has ponding after rain;Intertillage and weeding are not timely or intercropping tall stalk crops are also seriously affected;Robinia pseudoacacia (also infected with anthrax) near the orchard (within 20-25 meters) can aggravate the occurrence;The disease of strong trees is light, while that of weak trees is heavy;The incidence rate of trees with more sunburn fruits is high.[3]
three
Variety resistance: The infection degree of anthracnose varies greatly among different apple varieties.Among the existing cultivated varietiesnational glory、Red FujiThe disease is the most serious, and the disease of Golden Delicious, Marshal, Red Star and Green Banana is mild.[3]
Morbidity characteristics
The central diseased plant was first formed in the park, and then gradually spread around.The diseased fruits are divided into pieces and concentrated. The diseased fruits in the inner chamber of the crown are more than those in the outer part, and the diseased fruits in the middle part are more than those in the upper part.[6]
Prevention and control methods
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Agricultural control
Strengthen management and improve disease resistance of fruit trees
Attention should be paid to the measures to enhance the tree vigor, such as deep soil reclamation, more organic fertilizer application, and control the amount of nitrogen fertilizer application;Prevent water accumulation in the garden, select low stalk crops or green manure between rows of the orchard, or timely intertillage and weed control to reduce the humidity of the orchard;Reasonable close planting, fine pruning, especially reasonable summer pruning, to improve the ventilation and light transmission conditions in the orchard;Avoid using Robinia pseudoacacia as a protective forest in the orchard.[3]
Uproot the source of disease
In combination with winter pruning, the diseased and stiff fruits, dry and withered branches and diseased fruit stands under the trees shall be completely removed, and the diseased and withered bark shall be scraped to reduce the source of infection.In the early stage of the disease, the diseased fruit should be removed as early as possible, and the fallen fruit should be removed and buried intensively to reduce the source of disease and avoid repeated infection.[3]
Fruit bagging
Bagging can make the good fruit rate without diseases and pests reach more than 90%.The bagging time is generally about mid to late May.Before bagging, spray 2000 fold solution of pyrazolidinofen once;After bagging, Bordeaux liquid can be sprayed instead of the medicine to prevent and control the heart worm.[3]
Chemical control
Spray 3-5 ° Be sulfur stone mixture, 0.3-0.5% sodium pentachlorophenol mixture or Guokangbao 50-100 times solution before apple tree germination.The practice has proved that this method is effective in eliminating overwintering disease sources and reducing disease occurrence.[3]
In the growing season, especially before the onset of the disease, timely spraying to protect the fruit is an important measure to control the disease.Practice has proved that 200~240 times Bordeaux liquid can control the disease.Bordeaux liquid must be sprayed carefully and thoughtfully, and leather glue shall be added as an exhibition agent to improve adhesion and extend the efficacy period‘Jinguan 'and other varieties are sensitive to Bordeaux liquid, and they often cause drug damage or rust when used in young fruit stage, so other drugs can be sprayed instead.[3]
Generally, spraying starts from the young fruit stage (Siheshan usually starts from the middle and late May to the first ten days of June), and then once every 15-20 days, three or four times a year.To prevent drug resistance of bacteria, 50%AcetaminophenThe wettable powder can be used alternately for 600-800 times, with good control effect.Bordeaux liquid is still suitable in the early and late stages.In case of rain after spraying, Bordeaux liquid can not be sprayed in time. After rain, it can be sprayed with disinfectant to kill conidia produced in rainy season.Choose one of the following, or use alternately, the effect is also good.E.g. 40%CarbendazimGlue 800 times+40%chlorpyrifos 1500 times liquid (applied around the middle of May to cure apple ring rotLeaf curler, spider, etc.), or 70%Thiophanate methyl800 times, 50% carbendazim wettable powder 600 times, 25%TriadimefonThe wettable powder is 1000 times liquid.In order to improve the control effect, when using the above agents, it is better to add adhesive and 6501 developer to prevent the rain from washing and reducing the efficacy.[3]
The storerooms, baskets, boxes, etc. where apples are stored are sprayed with 50% carbendazim or 50% thiophanate methyl 200-500 times solution for sterilization, and then every cubic meter of space is ignited with 20-25 grams of sulfur, sawdust and 10% potassium chlorate, and fumigated for 2 days.Soak the fruit with 70% thiophanate methyl or 50% carbendazim 300-500 times solution for 1-3 minutes before storage.It is better to keep 1-2 ℃ low temperature during storage.[3]
Disease differentiation
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Apple anthracnose fruit is easy toApple ring rotThe diseased fruit is confused because both anthracnose and apple ring rot on the fruit will produce ring streak like spots.The two can be distinguished according to the following characteristics: the disease spot of anthrax is light brown at first, and then becomes dark brown. The disease spot is small and concave, and it is conical and deep into the pulp. The decayed part is funnel-shaped. The black particles on the surface of the disease spot are arranged in a concentric ring pattern. The disease tissue is soft and dry, evenly brown, and slightly bitter;The disease spot of apple ring streak is brown, with dark and light brown concentric rings. The disease spot is large, not sunken, and does not expand to the pulp into a cone shape, that is, the diseased part does not show a funnel shape, the surface of the disease spot is scattered with small black spots, the diseased tissue is rotten and juicy (water stains), the brown color is uneven, and has a slight taste of distiller's grains.[3]In terms of the occurrence time of the disease, the occurrence time of apple ring rot is later than that of anthracnose. The apple ring rot generally occurs in the near maturity period and storage period, and the occurrence time of anthracnose is mainly in the later stage of fruit growth.[7]
