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Citrus sapiensis, citrus stalk rot
Citrus resin disease is one of the important diseases of citrus. It has many names because of different parts of the disease. It is called tree finger disease or gummosis on the trunk, brown rot on the fruit and sand skin disease on the leaves. Citrus resinous disease is distributed all over the country!
Symptom
(1) Fruit damage: when the fruit is picked, especially in the process of storage and transportation, the root rot often occurs. At the beginning, there were water stains and light brown spots around the pedicel of the fruit, and then gradually turned to dark brown. The diseased part expanded to the navel one by one, and the edge was wavy. Because the diseased fruit rotted rapidly inside, first the core of the fruit rotted, and finally the whole fruit rotted, it was called "heart piercing rotten". The pericarp of the diseased part is firm and leathery.
(2) Damage of new leaves, saplings and young fruits: the surface of the diseased part produces small yellow brown hard colloidal dots (conidia of the pathogen), which are scattered or dense in pieces, called "sand skin". There are many cracks on the edge of the grain point on the young fruit, and the boundary with the healthy part is obvious. If the disease occurs late, it will have little effect. If it occurs early, the fruit growth is stagnant and stunted.
(3) Branch damage: if the pathogen infects the weak growth or the last year's branch is damaged by freezing, the resistance of the branch tip is slightly weak and does not form "sand skin". The surface is brown, and there is often a small drop of resin exudation at the junction of the diseased and healthy parts. When it is serious, it can make the whole branch wither, and countless small black particles are scattered on the surface of the withered branch.
The pathogen is the intercellular shell of xiangyangju, which belongs to ascomycetes
The occurrence rule of Citrus resinous disease is a kind of fungal disease. The pathogen overwinters on the diseased branches, diseased trunk or diseased bark with hyphae or conidia, which is the main source of the disease in the second year. The parasitism of the pathogen is not strong, and it can only invade when the growth of the host plant is weak or injured, which is the main reason for the occurrence of the disease after the citrus suffered from freezing injury.
The formation of sand skin or black spot is due to the invasion of a large number of pathogens into the host young tissue, but the young tissue has strong vitality and can produce defense response. It prevents the bacteria from going deep, so it grows into many black spots of sand skin or colloid.
Bad cultivation management and the disease
Poor cultivation management is closely related to the occurrence of the disease. All kinds of wounds caused by improper management are the main way of invasion. The disease of vigorous trees is mild, weak and easy to occur.
Preventive measures
(1) The main measures to prevent the disease are to strengthen the cultivation management, strengthen the tree vigor, improve the resistance of plants and do a good job in cold prevention.
(2) The diseased trees were found at the beginning of spring, and the diseased parts were scraped off as early as possible. Apply 200-300 times of 80% carbendazim wettable powder or 200 times of 70% thiophanate methyl wettable powder to the wound. In the whole year, two phases (may in the first half of the year and September in the second half of the year) were applied, and each phase was applied 2-3 times.
(3) Spray 0.5% Bordeaux solution once a year before germination of spring buds, 40% flusilazole 4000 times solution once in two thirds of falling flowers and in young fruit period, or 6000 times solution of 80% tebuconazole wettable powder, or 500-800 times solution of 80% mancozeb wettable powder. The mixed use effect of two kinds of agents is better in serious orchard.
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Source: Prime Minister Guo
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