Occurrence and prevention of citrus anthracnose

1 Citrus anthracnose

Citrus anthracnose is a worldwide disease, and it is also the most common disease that farmers' friends are most worried about. When the anthrax disease occurs seriously, it often causes a lot of defoliation, the tip is dead, the fruit is dead, the stalk is falling, the bark bursts, the tree is weak, the yield is decreased, and the whole plant is dead. During storage and transportation, it often causes a large amount of fruit rot, which affects the market supply.

Anthrax is a weak fungus. If the plant is weak, the plant is susceptible to anthrax under conditions such as high temperature and high humidity. If the temperature is low, rainy, and insufficient, the nutrients stored in the plant are consumed in large quantities, which reduces the plant's ability to resist stress. In addition, there is no bactericidal drug in the Qingyuan to prevent or prevent the anthrax.

2 symptoms of anthrax

Anthrax is mainly harmful to leaves, branches and fruits, and can also damage flowers, trunks and seedlings. When the disease is serious, it causes a lot of fallen leaves, and the branches dry up, causing the tree to decline and even the whole plant to die. Because of the different parts of the disease, the onset time is different, the symptoms are different, the most common and serious damages are:

(1) Anthracnose is a disease of leaves

A. Acute type (leaf type): the so-called acute type of anthracnose, which often occurs on the young shoots. The lesions often start from the tip of the leaf. They are initially water-stained dark brown, like boiling water, and later It is yellowish brown, cloud-like, and the edge of the lesion is not obvious. After the death of the diseased tissue, it is often a "V"-shaped plaque, which can also produce small black small grain spots, and the diseased leaves will fall off quickly. The disease is only 3-5 days from the beginning to the leaf detachment. The phenomenon that common blades fall off the ground. The shoots that have fallen off the leaves quickly die, and many vermilion and viscous liquid spots are produced on the diseased shoots.

B. Chronic (leaf type): Chronic (leaf type) symptoms appear mostly at the tip or near leaf edge of growing leaves or old leaves, round or nearly round, slightly concave, and the lesion is initially yellow Brown, later grayish white, brown or dark brown. The disease and health are obvious. When the weather is wet, many reddish and sticky small liquid spots appear on the lesions. Under dry conditions, black small spots appear on the lesions, scattered or arranged in a wheel pattern. This is the conidia disk and conidia of the pathogen. The diseased leaves fall off slowly.

(2) Anthracnose is a disease

Branching symptoms: starting from the axillary bud at the base of the petiole, the lesion is initially pale brown, elliptical; posterior to fusiform, grayish white, with a brown edge at the border of the disease, with black small spots on it. After the diseased part of the branch around the shoot, the diseased tip died from top to bottom. The young shoots sometimes have acute symptoms, often from 3 to 10 cm at the tip of the sudden onset, like boiling water, dark green, watery, 3 to 5 days after withering and blackening, then withered, with vermilion Small grain, the young leaves will wither and fall off.

(3) Anthracnose is a symptom of fruit stalk

Fruit stems are dry: usually in September, after the fruit begins to mature, the affected fruit stalks are chlorotic, yellowish, brown, and finally grayish and dry. When the lesions spread to the pedicle, causing the stalk, the fruit turns color and falls off early. Caused a large number of fruit drop before fruit picking.

During storage and transportation, rot: brown rot is started from or near the pedicle, and orange-red dots or mucus are produced on the lesion when wet.

(4) Anthracnose causes damage to flowers and fruits

Symptoms of flowers: After the pistil stigma is infested, brown rot and falling flowers often appear.

Fruit symptoms: The disease occurs in young fruit. The initial stage is dark green irregular lesions, and the diseased part is sunken. There are white mildew or vermilion small liquid spots on it. After expanding to the whole fruit, it becomes a black and stiff fruit hanging on the branches. The fruit is damaged, and it has three symptoms: dryness, tear stain and soft rot. The dry type is more in the waist of the fruit, round or nearly round, yellowish brown or brown, slightly sunken, leathery, the diseased tissue does not go deep into the skin; the tear marks are on the surface of the peel with tears like a tear. A lesion consisting of many reddish-brown small bumps; the soft-corruption occurs during storage, usually starting from the pedicle, initially in pale brown, and later becoming brown and rot.

3 citrus anthracnose disease conditions

The pathogens overwinter in the mycelium of the diseased part, and the diseased dry shoots are the main source of infection of the pathogens. In the following spring, the sub-follicles are produced, which are spread by wind and rain and insects, and invade from the stomata or wounds. The pathogen has weak parasitism and latent infestation characteristics, that is, the pathogen can be dormant after being invaded by the host, and the symptoms are only manifested when the vitality of the host tissue declines or declines.

High temperature and humidity are beneficial to the disease; winter and spring plants are frozen or affected by drought; or citrus orchards are affected; or garden soil is sticky, soil layer is shallow, organic matter content is low; or partial application of nitrogen fertilizer; or high groundwater level, poor drainage It is easy to reduce the plant's resistance to stress and easy to develop. Generally, the varieties of sweet orange, ponkan, banana, citrus, lemon, red orange, and orange are more serious. The incidence of the same susceptible variety is closely related to the strength of the tree.

4 Comprehensive prevention and control of anthracnose

Comprehensive measures to strengthen cultivation management, enhance tree potential, and improve disease resistance should be adopted.

(1) Improve the management of orchards. Do a good job in fertilizer management and pest control, antifreeze, anti-sunburn, etc., and avoid causing mechanical damage to the tree and maintain a strong tree. Cut off the pests and branches and long branches, remove the fallen leaves on the ground, and burn them intensively.

(2) Strengthen fertilizer and water management to improve plant vigor. Deeply change the soil, increase the application of organic fertilizer and phosphorus and potassium fertilizer, avoid partial application of nitrogen fertilizer; rectify the irrigation and drainage system, do a good job of flood control, drought prevention, antifreezing and pest control.

(3) Cut off diseased diseased leaves in winter, collect and burn, and eliminate wintering pathogens.

(4) Eliminate stagnant water. The orange orchards in which the anthracnose disease occurs are low-lying and have a lot of water. The paddy fields and flatland orange gardens should strengthen the construction of irrigation and drainage channels to reduce humidity and control the occurrence of diseases. It is best to plant ridges in paddy fields, and the flat orchards should be According to the terrain, 40cm deep criss-crossing drains are dug to effectively prevent the "water flooding" caused by "large flood irrigation" and typhoon.

(5) After cleaning the fallen leaves, spray 1-2 times of fungicide , once every 10 days. Pharmacy can be used 65% Dyson zinc wettable powder 600 times solution, 50% Dyson ammonium water agent 800-1000 times solution, 70% methyl thiophanate WP 800-1000 times solution, 50% carbendazim 800 times solution Wait, there is a certain effect.

(6) Chemical control: 25% pyraclostrobin 1500 times + 20% flucyclazole 2000 times.


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