Citrus mainly includes citrus scab, citrus canker, citrus anthracnose, citrus resin disease, red spider, rust tick and other pests and diseases. 1. Citrus scab: mainly harms leaves, new shoots and young fruits. Leaves are easily twisted, new shoots become short and twisted, and fruits are small and thick. It can be controlled with 70% thiophanate-methyl 800- 1000 times solution. 2, citrus canker: there will be oil spots on the branches, and it is easy to die when the condition is serious, which can be prevented by copper acetate.

I. Citrus scab

1, characteristics of the disease

Citrus scab will harm leaves, new shoots and young fruits. At the beginning of the disease, yellow spots in oil will appear on the leaves, which will become waxy yellow spots with the aggravation of the disease. When the disease is serious, the leaves are easily distorted. The new shoots will become shorter and twisted after infection, but the lesions are not obvious. The disease also easily leads to small fruit, thick skin, sour taste and abnormal development.

2, prevention and control methods

(1) Pruning should be carried out reasonably at ordinary times, and diseased branches and leaves should be cut off in time to enhance the permeability between plants. At the same time, it is necessary to strengthen fertilizer and water management and promote the development of new shoots to be more robust and orderly.

(2) Generally, 500-800 times of 80% Sheng Da M-45 wettable powder, 600-800 times of 77% Kede, 600-800 times of 50% carbendazim wettable powder and 800- 1000 times of 70% thiophanate methyl can be used for prevention and control. Generally, it can be sprayed when the flowers wither by 2/3 before the new buds of spring shoots germinate to 2mm long. Generally, 1 time can be controlled every 7- 10 days, and it can be controlled for 2-3 times continuously.

Second, citrus canker

1, the characteristics of the disease

At the early stage of the disease, yellow or dark yellow-green oil-soaked spots will appear on the back of the leaves, then the two sides of the leaves will swell out and have beige round spots, and then the epidermis of the spots will rupture into sponginess. At the later stage of the disease, the center of the affected area will be sunken and cracked like a crater, with a yellow halo around it. When it happens on branches, it happens most in summer and autumn, and dark green or waxy oil spots will appear in the early stage of the disease, but the expanded disease spots will be similar to those on leaves, which will lead to the death of branches in severe cases.

2, prevention and control methods

(1) Nitrogen fertilizer should not be applied alone, but phosphorus fertilizer and potassium fertilizer should be applied more to ensure the orderly growth of summer shoots and autumn shoots, and remove diseased branches and leaves in time.

(2) Generally, it can be used when the new shoots of young trees are pulled out more than 3cm. Generally, chemical agents such as calcium copper sulfate and copper acetate can be sprayed.

Three, citrus anthracnose

1, the characteristics of the disease

(1) Leaf spot type (chronic): It mostly occurs at the edge or near the edge of growing leaves and old leaves. When the climate is wet, dark green to yellowish brown spots will appear on the tip of the blade. When it is dry, the spots are slightly concave, the center is gray, and the black spots are arranged in a wheel shape.

(2) Leaf withered type (acute): It generally starts at the tip of the leaf, and at the initial stage it is a dark green lesion like boiling water, and then it gradually turns into a yellow-brown lesion, and the leaves are curled, which will cause shedding in severe cases. After the branches are damaged, the disease will die from bottom to top, and the color of the lesion is gray with black spots.

2, prevention and control methods

(1) Increase the application of organic fertilizer, prevent partial application of nitrogen fertilizer, and appropriately increase the application of phosphorus fertilizer and potassium fertilizer. Cut off dead branches of pests and diseases in winter and spring, remove sick and disabled bodies in time, burn them centrally or bury them deeply, and drain them in time after rain to avoid excessive humidity.

(2) After the disease spots appear, 5000 times solution of 10% difenoconazole water dispersible granules, or 45% prochloraz emulsion in water 1000 times solution, or 500 times solution of 70% thiophanate-methyl wettable powder+500 times solution of 75% chlorothalonil wettable powder can be used for prevention and treatment.

Four, citrus resin disease

1, the characteristics of the disease

At the early stage of the disease, there will be light brown waterlogging spots near the pedicel of the fruit, and then it will turn dark brown and extend to the navel. The core of the fruit will rot first, and then the whole fruit will rot. However, after new leaves, tender shoots and young fruits are damaged, small brown or dark brown hard glue spots will appear on their surfaces, and the growth of fruits will stagnate and the development will be poor.

2, prevention and control methods

(1) Strengthen tree vigor, improve plant resistance, and do a good job in cold protection. In areas with low temperature in winter, 1-3-year-old young trees can be cultivated before the temperature drops.

(2) Generally, before spring buds germinate every year, 400-500 times of 80% mancozeb wettable powder or 1000- 1500 times of 25% prochloraz emulsifiable concentrate can be used for control.

Verb (abbreviation for verb) Citrus Huanglongbing

1, the characteristics of the disease

The disease can occur in branches, leaves, flowers, fruits and roots, especially in summer shoots and autumn shoots. In the early stage of the disease, some new shoots will appear leaf yellowing (yellow buds), starting from the top leaves and then spreading downwards. Usually, the whole plant will become ill after 1-2 years. After leaf infection, there will be mottled leaves, thick and hard mesophyll, dull leaf surface and swollen veins. The fruit is deformed, dull, sour and of poor quality.

2, prevention and control methods

(1) Quarantine should be strengthened at ordinary times to prevent diseased seedlings and diseased ears from entering the orange orchard. It is also necessary to eradicate the diseased plants in time and check them carefully every spring, summer and autumn. If any diseased or suspected diseased plants are found, they should be dug up immediately and burned centrally.

(2) Because the transmission route of citrus Huanglongbing is seedlings and citrus psyllid, it is necessary to control citrus psyllid in time. When the new shoots are pumped to 1-2cm, the insecticide can be sprayed 1-2 times.

Six, citrus sooty blotch

1, the characteristics of the disease

After the disease, a layer of black coal stains will appear on the surface of leaves, branches and fruits, and then it will expand into a fluffy layer of black mold, which will seriously affect the photosynthesis ability of plants, lead to weak tree potential, affect fruit coloring and reduce fruit quality.

2, prevention and control methods

(1) At ordinary times, it is necessary to strengthen the management of gardens and prune them properly, so as to make the fields ventilated and transparent and enhance the tree potential. In addition, it is necessary to control aphids, whiteflies, aphids and other suction pests. Use 800- 1000 times of 40% methidathion EC, but it can't be used after the fruit is colored.

(2) When the citrus coal pollution is serious, 400 times solution of 50% carbendazim wettable powder can be used for prevention and control.

Seven, citrus scab

1, the characteristics of the disease

(1) Black star: The lesion is round and reddish brown in color. In the late stage of the disease, the edge of the disease spot is slightly raised, and the color is reddish brown to black, which is easy to cause fruit drop when the condition is serious.

(2) Black spot type: At the initial stage of the disease, the spots are light yellow or orange yellow, and then they expand into black, irregularly shaped severe lesions with many small black spots scattered in the center. When the disease is serious, the fruit surface will be covered by many combinations of diseased spots.

2, prevention and control methods

(1) Controlling the amount of nitrogen fertilizer can appropriately apply phosphorus fertilizer and potassium fertilizer to enhance the growth of trees. For low-lying and waterlogged land, it is necessary to drain water in time, remove too dense branches and leaves, reduce humidity and ventilate.

(2) Carbendazim and mancozeb can be used for control.

Eight, orange-brown stem rot

1, the characteristics of the disease

Fruits often start from pedicels. At the initial stage of the disease, it was a round yellow-brown lesion soaked in water, and at the later stage, the edge of the lesion was wavy and the color was dark brown. However, in the process of spreading the lesion to the navel, the core decays faster than the skin. Usually, when the lesion expands to 1/3- 1/2 of the fruit surface, the fruit core has all rotted.

2, prevention and control methods

(1) harvesting is not allowed after rain or when the morning dew is still wet. Mechanical damage to fruits should be avoided in the whole process of harvesting, handling, grading, waxing, packaging and storage.

(2) For the fruits that need to be stored, they need to be soaked in medicinal liquid 1 min when picking. Generally, fruits can be soaked with 50% Wanlide EC 2000-2500 times, 25% Dave EC 1000- 1500 times and 45% prochloraz EC 2000 times.

Nine, citrus acid rot

1, the characteristics of the disease

After the fruit is infected with citrus acid rot, orange round spots will appear, which will expand rapidly in a short time, resulting in soft rot of the whole fruit, soft diseased parts, easy peeling of the peel, white sticky substances in the later stage, and the whole fruit will rot out of water and have a rancid smell.

2, prevention and control methods

(1) Fruits should be harvested in sunny days. When harvesting fruits, care should be taken to avoid damaging the fruits. After harvesting, it can be ventilated in the shade for 4-6 days, and then put into storage. If rotten fruit is found, it needs to be buried or destroyed in time to avoid repeated infection.

(2) After the fruit is harvested, it can be soaked with prochloraz, prochloraz manganese salt and thiabendazole.

Ten, citrus foot rot

1, the characteristics of the disease

Citrus foot rot mainly harms roots and neck. After the onset, the affected area was brown, with distiller's grains smelly and glue flowing out. In the late stage of the disease, if the weather is dry, the diseased part will often crack. If the conditions are suitable, the lesion will expand rapidly. When the disease is serious, the disease spots will surround the whole trunk, leading to the death of citrus.

2, prevention and control methods

(1) It is necessary to strengthen field management, pay attention to drainage in low-lying and waterlogged areas, and choose disease-resistant rootstocks. When grafting, the position of grafting joint can be raised appropriately and should not be planted too deep.

(2) Scrape the rotten cortex of the diseased tree and some healthy tissues around it in time, and then apply Bordeaux solution, aluminum phosphide and other drugs on the incision.

XI。 Citrus macular disease

1, the characteristics of the disease

(1) Macular type: At the initial stage of the disease, 1 or several oil-soaked spots will appear on the back of the leaves. With the growth of leaves, the color of diseased spots will turn yellow-brown or dark brown, showing scab shape.

(2) Brown small round spot type: At the initial stage of the disease, there will be reddish-brown slightly convex spots on the leaves, and then gradually expand slightly, and the middle part is slightly concave, turning into taupe round to oval spots. In the late stage of the disease, the center of the affected part will turn gray, and the dark brown edge will be slightly raised.

2, prevention and control methods

(1) Apply more organic fertilizer, loosen soil and drain water in time, strengthen tree vigor and improve plant disease resistance.

(2) Generally, pesticides such as carbendazim, mancozeb and thiophanate-methyl can be sprayed after flowering.

Twelve, citrus gummosis

1, the characteristics of the disease

Citrus gummosis mainly occurs on the trunk, followed by the main branches, and can also occur on the branchlets. The lesion is uncertain, and the surface of the affected part is brown, waterlogged and cracked, with colloid. The fruit on the diseased tree is small and sour.

2, prevention and control methods

(1) Pay attention to ditching and drainage to improve the ecological conditions of orchards. We should strengthen the prevention and control of stem borers in peacetime, cover the ground in summer and whitewash the trunk in winter and summer.

(2) Scrape off the rough skin of the affected area, then cut several cracks longitudinally to the depth of xylem, and then apply 50% carbendazim wettable powder 100-200 times.

Thirteen, citrus oil spot disease

1, characteristics of the disease

Citrus oil spot disease mainly occurs on mature or nearly mature fruits, and irregular yellow and white spots of different sizes will appear. At the early stage of the disease, the oil cells in the plaque are prominent and the tissues in the oil cells are depressed downward. In the late stage of the disease, the oil cells in the spot atrophy and turn yellow-brown. Although oil cells themselves will not cause fruit rot, they are easily infected by Penicillium and Penicillium after the death of diseased spots, leading to fruit rot.

2, prevention and control methods

(1) You should not pick fruits in rainy days or when the dew is still wet, but you should handle them carefully during picking, selection and packaging to avoid all kinds of mechanical damage to the fruits.

(2) After the fruit is picked, it should be pre-stored for 2-3 days before packaging, and the peel should be prevented from being damaged during transportation, packaging and transportation.

Fourteen, citrus sunburn

1, characteristics of the disease

After the immature fruit is damaged, the top color of the fruit is yellow-brown, and the development is stagnant. After the mature fruit is damaged, the shape of the fruit is not straight, the surface of the peel is rough and the dry scar is hard. For lightly damaged fruits, the burn site is limited to the peel, while for severely damaged fruits, the center of the burn site is cork-shaped, which will destroy the juice cells, leading to the shrinkage of juice cells, less juice and weak taste, and poor quality.

2, prevention and control methods

(1) Choose citrus varieties with less sunburn and build shelterbelts in the southwest of the orchard to reduce the exposure to the scorching sun when planting in the orchard.

(2) During high temperature and drought, water spraying can be used to keep soil moisture, increase relative humidity and reduce temperature. If damaged fruits are found, lime milk can be applied, and slightly damaged fruits can generally return to normal.

Fifteen, citrus fruit cracking

1, the characteristics of the disease

Citrus cracking is mostly caused by rapid weather change and sunburn. Usually, when the weather is sunny and rainy, the water content in the soil will be high or low, and the water content in fruits will also be affected. When the pulp absorbs water and expands faster than the peel can bear, the peel will crack.

2, prevention and control methods

(1) Supplement boron fertilizer and calcium fertilizer. Calcium fertilizer can enhance the toughness of pericarp, pectin of pericarp cells and anti-swelling ability. If boron deficiency causes plants to absorb calcium fertilizer, it will indirectly lead to fruit cracking. Therefore, supplementing adequate boron and calcium fertilizer can reduce fruit cracking.

(2) Remove diseased fruits in time to prevent pathogens from invading and parasitizing. It can also be combined with the control of rust ticks and red spiders, and sprayed with 0.3-0.4 degree lime-sulfur mixture 1-2 times on the crown, which is not suitable for high temperature and scorching sun, and can be carried out in the morning and evening.

Sixteen, citrus red spider

1, the characteristics of the disease

Starscream will gather on leaves, fruits and twigs to suck juice, and the young leaves will suffer the most. In severe cases, the leaves will lose their luster and turn gray, and the leaves will be covered with dusty molting shells, which will lead to early defoliation and easily affect the tree potential.

2, prevention and control methods

(1) Do a good job of pruning and cleaning the winter garden. Prune the overgrown branches, pests and diseases, and shade branches in time, burn them centrally, and clean up the garden with engine oil emulsion.

(2) Generally, 2% avermectin 1000- 1500 times solution and 57% propargite 2000 times solution can be used for control.

Seventeen, citrus rust tick

1, the characteristics of the disease

Citrus rust ticks will suck the juice from the back of leaves and the surface of fruits, which will turn the back of leaves and the surface of fruits into dark brown or copper green, and in severe cases, will cause a lot of fallen leaves.

2, prevention and control methods

(1) In winter, combining with plastic pruning, we cut off dense branches, leaves rolled by diseases and insect pests and sporadic winter shoots, creating a ventilated and light-transmitting environment for orchards and reducing overwintering insect sources.

(2) Generally, 65% zineb wettable powder 600-800 times, 5% Abamectin SC 1000-2000 times and 20% DDVP wettable powder 1200-2000 times can be used for spray control.

Eighteen, citrus aphids

1, the characteristics of the disease

Citrus aphids mainly harm shoot tips, which will damage shoot tip tissues by sucking nutrient solution and form uneven shrinkage, which will affect fruit quality and yield.

2, prevention and control methods

(1) branches damaged by aphids need to be cut off in winter and early spring, and natural enemies such as ladybugs, lacewings, jumping bees, syrphids and aphids can be reasonably protected and utilized.

(2) Spraying pesticides such as nicotine, rotenone, dimethoate and pyrethroid in time for control.

Nineteen, citrus root nematodes

1, the characteristics of the disease

After the root system is damaged, the branches will become shorter and weaker, the leaves will become smaller, the fruit setting rate will decrease, and the fruit will become smaller. When the root system is seriously damaged, it will cause the leaves to turn yellow, and the leaves will be curled and dull, and then they will dry up and fall off or the branches will wither, and then the whole plant will die.

2, prevention and control methods

(1) It is necessary to cultivate disease-free seedlings. If new citrus is planted in the diseased area, it is generally necessary to plow the soil 1-2 months in advance, and turn the soil layer containing nematodes to the surface, so that it can be exposed to the sun and reduce the incidence. At ordinary times, it is necessary to remove the root of the disease in time, increase the application of organic fertilizer, and enhance the disease resistance of plants.

(2) For seedlings with mild disease, root system can be soaked in warm water at 50℃ for 10 minute, and then planted. When planting, nematicides can be sprinkled around the citrus. If root nematodes are found in the growing period of citrus, root irrigation can generally be carried out.