Common citrus diseases include sooty disease, Huanglongbing, resin disease, anthracnose, canker, scab and other types. 1. Sooty stains: Black sooty stains appear on leaves, branches and fruit surfaces. The stains will gradually expand into a black mold layer. When the disease is severe, the photosynthesis of the plant will be affected and the quality of the fruit will be reduced. 2. Huanglongbing: When new shoots become infected, the leaves will turn yellow. The disease starts from the top leaves and spreads downward. After the leaves become infected, the mesophyll will become thicker and harder, and the leaf veins will become swollen. 3. Resin disease: In the early stage of the disease, light brown water-soaked lesions appear near the fruit base, and the lesions will gradually expand to the navel, causing the fruit to rot.

1. What are the common diseases of citrus?

1. Sooty stains

(1) Sooty stains will appear on the surface of leaves, branches and fruits ( Black), the stain will gradually expand into a black mold layer (velvety). When the disease is severe, the photosynthesis of the plant will be affected.

(2) After the disease occurs, the tree vigor will weaken, affecting fruit coloring and reducing fruit quality.

2. Huanglongbing

(1) The roots, leaves, branches, flowers, and fruits of plants can all be affected, especially the symptoms are more obvious in summer and autumn tips.

(2) In the early stage of the disease, the leaves on some new shoots will begin to turn yellow (yellow tips). The disease will start from the top leaves and spread downward. After 1-2 years, the entire plant will become sick.

(3) After the leaves are infected, the leaves will be mottled, the surface is dull, the mesophyll becomes thick and hard, and the leaf veins are swollen.

(4) After the fruit is infected, it will grow abnormally, lose luster, taste sour, and reduce quality.

3. Resin disease

(1) In the early stage of the disease, light brown water-soaked lesions appear near the fruit base. After a period of time, the lesions expand to the umbilicus and become It is dark brown. At this time, the core of the fruit rots first, and then the whole fruit rots.

(2) After new leaves, young shoots, and young fruits are damaged, small dark brown (or yellowish brown) hard gelatin spots will appear on their surfaces, and the fruit will stop growing at this time.

4. Anthracnose

(1) Leaf spot type

① It is a chronic disease and is prone to the disease on growing leaves, edges of old leaves or near the edges. , when the environment is relatively humid, water-soaked dark green to yellow-brown lesions will appear on the leaf tips.

② After the environment dries, the lesions will become slightly concave, the middle color will turn gray-white, and there will be small black dots arranged in a ring shape.

(2) Leaf wither type

① It is an acute disease, usually starting from the leaf tips. Dark green lesions (like boiling water burns) will appear in the early stage of the disease. After a period of time, Slowly turn into yellow-brown lesions, and the leaves will curl or fall off.

② When the branch tips are affected, the diseased spots will die from bottom to top, and the diseased spots will be gray-white in color with small black spots.

5. Canker disease

(1) In the early stage of the disease, small oil-soaked spots appear on the back of the leaves, and the color is yellow or dark yellow-green. Later, both sides of the leaves will gradually bulge, and Beige round lesions appear, and the surface of the lesions will break into a sponge shape.

(2) In the later stage of the disease, the center of the diseased area is sunken and cracked like a crater, with a yellow halo surrounding it.

(3) Most of the branches are affected in summer and autumn. Small oil-stained dots will appear in the early stage of the disease, and the color is dark green or waxy yellow. Later, they will gradually expand into diseases similar to those on the leaves. Spots, branches will die when the disease is severe.

6. Scab disease

(1) Leaves, new shoots, young fruits and other parts will be affected.

(2) When the leaves are infected, small oil-soaked yellow spots will appear in the early stage of the disease. When the disease worsens, the spots will turn to waxy yellow, and then the leaves will easily become twisted and deformed.

(3) When new shoots are infected, the length becomes shorter and twisted, but the disease spots are not obvious.

(4) When fruits are infected, they will become smaller, develop deformed, the skin will become thicker, and the taste will become sour.

2. How to prevent and control common citrus diseases

1. Sooty rot disease

(1) Strengthen management, prune appropriately, and spray 40 chlorphosphos emulsifiable concentrate 800-1000 times liquid is used to control piercing-sucking mouthpart pests (drugs cannot be used after the fruit is colored), such as whiteflies, aphids, aphids, etc.

(2) When the condition is serious, spray 50 times of carbendazim wettable powder 400 times.

2. Huanglongbing

(1) Strengthen quarantine to prevent diseased seedlings and ears from entering the orange orchard, and eradicate diseased plants in a timely manner. The three shoot stages of spring, summer and autumn are required every year. After careful inspection, if any diseased or suspected diseased plants are found, they should be dug out and burned together.

(2) When the length of the new shoots reaches 1-2 cm, spray insecticides 1-2 times to prevent and control citrus psyllid, which can reduce the transmission route.

3. Resin disease

(1) Take cold protection measures. If the temperature in the planting area is low after winter, 1-3 year old saplings should be treated before the temperature drops. Carry out soil cultivation, which can enhance the vigor of the tree and improve the resistance of the plant.

(2) Spray 400-500 times of 80th generation mancozeb wettable powder or 1000-1500 times of prochloraz 25 EC before the spring buds sprout every year.

4. Anthracnose

(1) Apply more organic fertilizers, phosphorus and potassium fertilizers, and avoid partial application of nitrogen fertilizers. In winter and spring, dead branches, diseased and insect-infested branches should be cut off, and diseased branches should be burned or buried deeply. Drainage should be done after rain to prevent excessive humidity in the garden.

(2) After discovering the lesions, you can spray 10 difenoconazole water-dispersible granules 5000 times liquid, or 45 prochloraz water emulsion 1000 times liquid, or 70 thiophanate methyl Wettable powder 500 times liquid +75 chlorothalonil wettable powder 500 times liquid.

5. Canker disease

(1) Apply more phosphorus and potassium fertilizers, avoid partial application of nitrogen fertilizers, and promptly remove diseased branches and leaves to ensure neat growth of summer and autumn shoots.

(2) When the length of the new shoots of the saplings exceeds 3 cm, spray calcium copper sulfate, copper acetate and other chemicals.

6. Scab disease

(1) Prune the branches appropriately to enhance the permeability between plants. If diseased branches and leaves are found, they should be pruned in time.

(2) Strengthen water and fertilizer management to promote the development of new shoots that are neater and stronger.

(3) Before the new shoots sprout and reach 2 mm in length, and when 2/3 of the flowers have faded, spray 50% carbendazim wettable powder 600-800 times, or 77% to kill Get 600-800 times liquid, or 70 thiophanate methyl 800-1000 times liquid, or 80 M-45 wettable powder 500-800 times liquid, spray once every 7-10 days, spray continuously for 2- 3 times.