What are the symptoms and control methods of cyclamen wilt disease?
Cyclamen
The cyclamen, which can serve as the city flower of Qingzhou City, Shandong Province, must have an image and connotations different from other flowers. At present, this flower has become a relatively commonly cultivated cut flower, but many flower enthusiasts are often startled by the sudden attack of wilt disease while growing cyclamen, causing them to be in a flurry. So what should be done when encountering this flower disease? Below is a detailed analysis of the causes and control measures of cyclamen wilt disease.
I. Symptom manifestations
The disease is caused by Fusarium. In the early stage of infection, some leaves of the plant turn yellow. On sunny days, the leaves wilt, can recover at night, wilt again during the day, until death. The petiole part is edema-like, sometimes with longitudinal cracks in the epidermis. Under conditions of high air humidity, cotton-like white colonies grow at the diseased spots, sometimes with a pale red tinge. Wilt disease is a soil-borne disease, and the affected parts turn brown and necrotic from bottom to top. When the corm of a diseased plant is cut crosswise, the vascular bundles can be seen turning brown in the cross-section, and the corm generally does not rot.
II. Transmission routes
Wilt disease overwinters as mycelium or chlamydospores in the soil with diseased residues or attached to seeds. The pathogen generally invades from young roots or wounds, enters the vascular bundles, blocks the vessels, and produces toxic substances, causing the corm and leaves to turn yellow and die. Under high temperature and humid conditions, the disease is more severe, and the pathogen spreads through water flow.
III. Conditions for onset
In greenhouses where cyclamen has been cultivated for many years, because the soil carries the pathogen, the pathogen enters the roots through the bottom holes of the pots during watering and infects them. Plants with weak growth and wounds on the roots are more likely to be infected. Under protected cultivation, the disease occurs year-round, with July and August being the peak period of onset.
Cyclamen
IV. Control measures
After wilt disease occurs, most chemicals have no obvious therapeutic effect. In production, prevention should be the main approach, with comprehensive treatment.
1. Facility disinfection
After all cyclamen are sold, thoroughly clean the greenhouse and sterilize it, removing dead leaves, spent flowers, weeds and other waste before disinfection. During the growing season, it can be done before the cyclamen flower buds extend out of the leaves, using chlorothalonil smoke agent to fumigate the greenhouse 3 times, with the first and third intervals of four to five days, and the second and third intervals of 7 to 10 days. For a solar greenhouse with an area of 1 mu, use three to four boxes each time. Light the smoke agent after 5 p.m., keep the greenhouse sealed for more than 4 hours, then ventilate.
2. Seed disinfection
At sowing, soak with 1000-fold potassium permanganate for 12 hours, rinse off the liquid with clean water, then sow.
3. Substrate disinfection
For conventional substrate disinfection, one week before potting, mix 500 g of dithane or carbendazim per cubic meter into the soil, or spray with 1000-fold potassium permanganate. Alternatively, use metham-sodium mixed into the soil one month before potting, at 20 to 30 g per square meter. After disinfection, take care to protect the substrate to prevent secondary contamination. Seven days before use, turn the disinfected substrate thoroughly to aerate it and volatilize residual chemicals.
4. Ground disinfection
First thoroughly scrape and clean the ground, then spray with 1000-fold potassium permanganate, or use 3000 g of dithane or carbendazim per mu mixed with an appropriate amount of clean river sand and spread evenly on the ground. Use metham-sodium at 30 to 60 g per square meter, add an appropriate amount of clean river sand and broadcast it, then deep-turn 20 cm and cover with plastic film. At a soil temperature of 10°C, fumigate for 27 days; at 15°C, fumigate for 20 days; at 20°C, fumigate for 16 days; at 25°C, fumigate for 13 days.
5. Pot disinfection
Soak used pots in 1000-fold potassium permanganate for 2 hours; if possible, use new pots.
6. Off-ground cultivation in flower pots
If conditions permit, set up elevated special flower beds or use flower pot stands to keep the pots off the ground.
7. Chemical control
When diseased plants are found, either remove and destroy them, or use 500 g of 70% thiophanate-methyl, add 5 kg of clean river sand, mix evenly with uncontaminated sieved honeycomb briquette cinders, and dry-spread on the potting soil of diseased plants, once every 3 days, for 3 consecutive applications. Use 70% thiophanate-methyl 800 to 1000-fold solution, 80% carbendazim 800 to 1000-fold solution, 800-fold solution of Shadufan, and benomyl 2000-fold solution alternately for root drenching, with 100 ml of medicinal solution per plant each time, once every 7 to 10 days.
If you did not read the above introduction, I believe that anyone who is not a professional flower grower would definitely not disinfect the seeds! In fact, wilt disease is a disease that many cut flowers are prone to, but as long as timely remedial measures are taken, they can still be bright and gorgeous!
What diseases does cyclamen have, and how to prevent and control cyclamen diseases
During the growth of cyclamen, some diseases and insect pests often occur. Below, the editor will share with everyone what diseases cyclamen has and how to prevent and control cyclamen diseases.
1. Bacterial leaf rot
The disease can occur at the petioles, buds, and corms of cyclamen. At first, the petiole has water-soaked diseased spots, then the lesions expand into black patches, and then cause rot. The rotting part develops along the leaf veins toward the leaf tip, causing the entire leaf to rot, and the leaf yellows and dies. The symptoms expand to young flower buds and leaf buds, and spread along the conductive tissue to the corm, causing it to rot and die, and the aboveground part to wilt. Cyclamen seedlings can be infected; when the first leaf unfolds, water-soaked spots can appear on the hypocotyl, causing the seedling to die. One infected and dead seedling can infect other healthy plants. Hands, water, flower pots, etc. that have contacted diseased plants can all be sources of infection, and seed-borne bacteria are also a main route of infection.
Control methods: Eliminate natural sources of infection, prevent seed transmission, and strengthen seed quarantine. Before sowing, soak in 0.5% sodium hypochlorite for 3 hours for disinfection, then rinse with clean water for 1 day and night; remove diseased leaves or plants at any time and burn them in a centralized manner. At the same time, spray chemicals and maintain environmental hygiene. During maintenance operations, try to keep the environment dry, and do not use hands that have handled diseased plants to contaminate healthy plants again; for chemical control, spray 150 to 200-fold Bordeaux mixture, and apply oxytetracycline 2000-fold solution or streptomycin 3000 to 4000-fold solution to wounds after leaf or flower removal for preventive effect.
2. Bacterial soft rot
The disease mostly occurs during the high-temperature and humid period from July to August. On sunny days after rainy days, the aboveground part rapidly wilts and dies, the corm softens and rots, and the buds and petiole bases also rot at the same time. The rotting parts emit a foul odor, and there is a slimy exudate on the upper part of the corm. Soft rot is a soil-borne disease, and incomplete soil disinfection can easily lead to the occurrence of this disease.
Control methods: The soil used for potting must be thoroughly disinfected. Evenly sprinkle 400 to 500 ml of formalin dilution diluted 50 times with water into each cubic meter of culture soil, then pile the soil, cover it with plastic film, keep it sealed for 48 hours, then remove the covering and spread the soil out. It can be used after the formalin gas has completely volatilized. Wear a mask and gloves during disinfection to prevent the chemical from being inhaled or contacting the skin. Another method is heat disinfection: put the prepared culture soil into an iron wok and burn it over fire for 20 minutes, which can also achieve a disinfection effect; for chemical control, choose 1000-fold streptomycin solution or 150 to 200-fold Bordeaux mixture to regularly spray the rhizosphere soil of key diseased plants and surrounding healthy plants, about once every half a month, for 2 to 3 consecutive sprays, which can control the spread of the disease.
3. Anthracnose
Anthracnose can occur at any time of the year. At the initial stage, small water-soaked spots appear on the leaves, and then the spots gradually expand to form concentric circular ring-like lesions. July to October is the peak period for leaf bud and flower bud differentiation of cyclamen. At this time, small water-soaked spots may also appear on young flower buds, and the spots extend upward and downward to form spindle-shaped lesions, which can cause the flowers to die.
Control methods: The anthracnose pathogen prefers high temperatures. By the time the buds die, it is already too late to control it, so early prevention and early treatment are required, and eliminating the source of infection is the primary measure. This disease is mainly transmitted by seeds. Seeds must be thoroughly disinfected with sodium hypochlorite, potassium permanganate, etc., and seeds must absolutely not be collected from diseased plants. Water and fertilize reasonably. Before onset, spray 160-fold Bordeaux mixture, once every half a month, for 2 to 3 consecutive sprays. In the early stage of onset, spray 70% thiophanate-methyl wettable powder or mancozeb 800 to 1000-fold solution.
4. Gray mold
The gray mold pathogen has very strong vitality. Generally, the disease occurs more from the rainy season to the flowering period after October. On cloudy and rainy days in June to July, if the plants are weak and spindly, or old leaves have wounds, the pathogen will invade. Usually, the disease first occurs at the petiole of old leaves. After October, if the greenhouse is closed and the temperature is high, the disease can also occur. At the initial stage, the old petioles on the outer side of the plant rot and black mold appears, then adjacent petioles and peduncles are also affected one after another, quickly infecting the entire plant, ultimately causing the corm to rot and the whole plant to die.
Control methods: This disease is extremely prone to occur under humid conditions, so moisture prevention is the main countermeasure. Do not water too much, open windows for ventilation to keep air circulating, and keep the interior clean to reduce pathogen density. Chemical control mainly involves early and regular spraying of a mixed solution of captan 800-fold and benomyl 2000-fold in late May before the rainy season and in late September before entering the greenhouse.
5. Wilt disease
Wilt disease occurs mostly in summer and autumn. In the early stage of onset, part of the leaves lose vitality, wilt, and turn yellow. Afterward, the yellowed leaves gradually increase. On sunny days after rain, the whole plant withers. This condition can return to normal at night, then wilt again during the day, until the plant dies.
Control methods: This disease is mainly spread through soil, so soil, flower pots, etc. must be thoroughly disinfected to eradicate the source of infection. At the same time, water reasonably, because too-large flower pots, or potting soil that is too dry or too wet, can easily lead to wilt disease. Diseased plants found must be burned immediately or buried deeply, and the flower pots must be disinfected again. Chemical control mainly uses benomyl 2000-fold solution for root drenching, and captan 800-fold solution for spraying during the growing season.
6. Leaf spot
Leaf spot generally occurs mostly between July and October, with brown lesions on the leaves.
Control methods: When diseased plants are found, promptly remove diseased leaves, and at the same time spray with amobam 800 to 1000-fold solution or Bordeaux mixture 150 to 200-fold solution.
7. Bacterial bud rot
The bud rot pathogen prefers low temperatures and mostly occurs during the cold period from November to March of the following year. Cyclamen is more susceptible to the disease after being frozen, and its symptoms are also rotting of leaves, buds, and corms.
Control methods: Thoroughly disinfect seeds, and regularly spray 150 to 200-fold Bordeaux mixture for control.
8. Root-knot nematode disease
Root-knot nematodes invade the roots of seedlings, causing many large and small nodular growths on the main roots and lateral roots. The nematodes suck sap inside the nodules. Infected plants show malnutrition, stunting, small and wrinkled leaves, clustered growth, and then gradually wither, with root necrosis.
Control methods: Disinfect the soil before planting. The method is to first stir-fry the soil in an iron wok for 20 minutes, take it out when the soil becomes dry and whitish, and use it after cooling. At the same time, use 0.75 g of fenamiphos per pot. After onset, irrigate the rhizosphere soil of cyclamen with 8% dichlorvos 1000-fold solution.
Further reading:
Cyclamen cultivation methods, fertilization techniques, pest and disease control, flower language and legends
Cyclamen care methods
Cyclamen generally breaks dormancy from late August to early September. At this time, it should be placed in a cool and ventilated place for care. As the leaves grow, gradually increase light, watering frequency, and watering amount. From the early bud stage of cyclamen until the peduncle elongates 1 cm, use a sprayer to spray a 1 ppm—5 ppm gibberellin solution directly on the young buds to promote earlier flowering. The gibberellin concentration should not be too high, otherwise the peduncles will grow excessively and droop, and deformed flowers will increase. The flowering period of cyclamen is generally from October to May of the following year. During flowering, maintain a room temperature of 12°C—15°C and a relative humidity of 60%—75%, which can prolong the flowering period. One flower can stay open for more than 20 days, and one pot of flowers can bloom for 4 months—6 months. If the room temperature is higher than 18°C, the stems will grow excessively, the flowers will droop, and the flowering period will be shortened; if the room temperature is lower than 10°C, growth will slow down and the flowers will be small. During flowering, watering should be properly controlled, and it is enough to keep the potting soil moist. Too much watering can cause the flowers to fade early. When watering, do not splash water onto flower buds and tender leaves to avoid rot. Fertilization should be stopped during flowering, otherwise it will cause the flowers to fade early. Also pay attention to frequently turning the pot position so that the leaves and flowers receive light evenly and the plant shape remains upright and beautiful.
The quality of cyclamen varieties directly affects their ornamental value and the difficulty of care. Therefore, imported F1 generation cyclamen with concentrated flower clusters, thick petals, good texture, and compact and glossy leaves should be selected. Cyclamen on the market includes two major strain groups: Japanese and European-American. Japanese strains have particularly brilliant flower colors, while European-American strains have large plant shapes and compact leaves.
Water: Watering should be properly controlled. Too much water will cause root rot. Water again when the flowers and leaves slightly wilt. Watering can be done by soaking water from the bottom of the pot; do not pour too much water on the leaf surface.
Light: Cyclamen should be placed in places with sufficient light such as windows and balconies, and the pot position should be changed frequently. Sufficient light can make the flowers more brilliant and the leaves more glossy. Although cyclamen belongs to the Primulaceae and is relatively shade-tolerant, long-term insufficient light can easily make cyclamen leaves turn yellow.
Ventilation: Cyclamen likes ventilation. Smoke, dust, and stale air can cause petals to dry and fall off, but it should not be placed directly in a draft.
Temperature: A room temperature above 5°C can allow cyclamen to grow normally. When the room temperature is on the low side, cyclamen can maintain a longer flowering period, but flowering is slow; when the room temperature is on the high side, flowering is fast, but the flowering period is short.
Humidity: Humidity should be maintained at 60%-70%. Too little humidity will make the flowers smaller, and too much humidity will cause gray mold and other fungal diseases on petals and leaves. It is strictly forbidden to spray water on the petals, otherwise the petals will rot.
Fertilizer: Fertilize twice a month. Imported or domestic compound fertilizer can be used, 5~8 granules each time, placed 2 cm deep in the substrate.
Home care of cyclamen
It is suitable to buy corms in August-September. Choose corms with a diameter of more than 4 cm and plump central leaf buds and flower buds. If buying potted flowers, they can be purchased from November to February. Choose potted flowers with robust plants, green and thick leaves, clear patterns, no wrinkles, no curled edges, more than 10 unfolded leaves, and many flower buds at the top of the corm (bud tips are round and papillate).
Basic habits: likes a cool and humid environment.
Temperature: The suitable growth temperature is 10-20°C. Below 5°C, growth is slow; at 0°C, frost damage can occur; above 30°C, growth stops and the plant enters a dormant state.
Light: Likes light. Below 28°C, expose it to as much sun as possible.
Water: Keep the potting soil moist but not too wet to prevent root rot.
Soil: Likes loose and fertile neutral soil, pH 6—7.
Fertilizer: Nitrogen fertilizer should not be excessive. You can use commercially available special fertilizer for cyclamen and follow the instructions. You can also use compound fertilizer granules with nitrogen:phosphorus:potassium = 20:20:20 together with potassium dihydrogen phosphate foliar fertilizer.
Cultivation points:
November to March is the flowering period of cyclamen. Potted flowers should be placed in front of a south-facing window or 1 meter in front of a south-facing enclosed balcony where light can be seen. Keep the room temperature above 10°C, keep the potting soil moist, and water once every half a month with 1% potassium dihydrogen phosphate foliar fertilizer, so it can bloom continuously. In rooms without heating facilities, pay attention to preventing low temperatures and cold drafts. You can cover the whole pot with a transparent plastic bag and place it in a warm and bright place. When the temperature is high at noon, open the plastic bag for ventilation. It can bloom from February to March.
From April to May, when the flowering period is about to end, remove spent flowers early and gradually place the plant in outdoor sunlight. Water once a week with 1% compound fertilizer solution. New leaves will soon grow, old leaves will fall off, and the corm will also enlarge. If aphids occur, use a brush or cotton swab dipped in water to brush them off; if leaves are found to shrink and turn yellow, bury 1~2 g of carbofuran along the edge of the pot to kill root-knot nematodes.
In June, water and fertilizer management is the same as in May. When the temperature is high, place it in a shaded place. Some potted flowers lose their leaves after flowering and enter dormancy until September. At this time, place them in a cool and ventilated place, keep the potting soil slightly moist, and do not fertilize.
From July to August, the north enters the high-temperature season, so water should be controlled and fertilizer stopped. Non-dormant plants should be placed on an east-facing or north-facing balcony, exposed to the sun for more than one hour every morning, or placed under tree shade. At this time, new leaf buds and flower buds will grow at the top of the corm. If rot disease (gray mold) occurs, spray and drench with 75% chlorothalonil wettable powder 1000-fold solution.
In September, dormant corms begin to sprout. Old plants more than two years old can have their potting soil changed, and newly purchased corms can also be planted at this time. When planting, first place 2~3 cm thick charcoal residue or ceramsite or coarse gravel at the bottom of the pot, then add culture soil. Old plants should be planted with the soil ball. After planting, the pot surface should be high in the center and low around the edges, with the corm exposed 1/2 above the soil surface. Water thoroughly the next day and place in a shaded place for care. After new buds grow, light can be increased.
In October, it enters the vigorous growth period and should be placed in sunlight for care. Water once a week with 1% compound fertilizer solution, and spray once with 1% potassium dihydrogen phosphate foliar fertilizer. Move indoors before Frost's Descent, and it can bloom in November.
Propagation
Generally propagated by sowing. The soil must be disinfected before sowing, and light must be avoided from sowing to emergence. Emergence takes more than a month, and seedlings grow slowly, requiring more than a year to bloom. It is best to directly buy potted flowers sold by reputable flower merchants, which can save a lot of trouble during planting.
Objective evaluation of advantages: beautiful flowers; long flowering period. Disadvantages: afraid of heat; potting soil must not be too wet (better on the dry side); does not like heavy fertilizer.
I. Symptom identification of several major diseases
(1) Soft rot is a bacterial disease. This disease mostly occurs in the high-temperature and humid June-September period in summer. On sunny days after rainy days, the aboveground part rapidly wilts and dies. The buds and petiole bases initially appear water-soaked, then turn brown and soft-rot, and the corm also softens and rots. The rotting parts emit a foul odor and have a grayish-white paste-like bacterial ooze.
(2) Bacterial leaf rot is a bacterial disease. This disease can occur on the leaves, petioles, buds, and tubers of the plant. When leaves are affected, water-soaked spots first appear at the leaf base, then expand, turn blackish-brown and rot, and spread until the entire leaf rots. When petioles are infected, water-soaked spots first appear, then the lesions expand into black patches, then cause putrefaction, and the leaves yellow and die. The vascular bundles of the diseased petioles turn brown and spread to the tuber, causing young buds to turn black and form bud blight. On the tuber, the vascular bundles at the bud points turn brown. With further development, the interior of the stem rots, or the rotting part forms sunken cracks and dries out.
(3) Wilt disease is a fungal disease. This disease mostly occurs in summer and autumn during the latter half of cyclamen growth. Initially, some leaves lose vitality, wilt, and turn yellow. Afterward, the yellowed leaves gradually increase. On sunny days after cloudy and rainy days, the whole plant withers. The vascular bundles at the petioles or corms of diseased plants turn brown. When humidity is high, pink mold layers are produced on the diseased parts.
(4) Anthracnose is a fungal disease. This disease mainly harms the leaves of cyclamen. At the initial stage, small water-soaked spots appear on the leaves, then expand into concentric ring-patterned round spots. The center of the lesions is light brown or grayish-white, and the edges are purplish-brown or dark brown. Many small black dots are produced in the lesions. In severe cases, it can cause the leaves to die.
(5) Gray mold is a fungal disease. It mainly harms leaves, petioles, and flower stalks. In the early stage of leaf disease, water-soaked streaks appear at the leaf edges, dark green in color, and gradually spread to the entire leaf. The leaves turn brown, and finally dry up or rot. After petioles or peduncles are infected, water-soaked rot occurs, and then they bend and droop. If environmental humidity is high, a gray mold layer grows on the diseased parts.
(6) Root-knot nematode disease is caused by infection by various root-knot nematodes, including southern root-knot nematode, northern root-knot nematode, and peanut root-knot nematode. After cyclamen corms are infected, large nodular growths form. After the root system is infected, many nodular growths of varying sizes form. Root nodules are initially pale yellow with a smooth surface, then turn brown with a rough surface. When root nodules are cut open, white granular substances can be seen, which are nematodes. The aboveground part shows stunted plants, yellowing leaves, and in severe cases, leaf death.
(7) Viral disease. The pathogen causing cyclamen viral disease is mostly cucumber mosaic virus. This disease can occur from the seedling stage to the flowering stage. The plant leaves appear wrinkled, uneven, and mottled. Leaf edges curl downward or upward; leaves are small and thick, brittle, and easily broken. Petioles are short and appear clustered. Sometimes prismatic protrusions on leaf veins or nodular growths on the leaf surface can be seen. Streaks or spots form on petals, and flowers are deformed or even degenerate. Diseased plants are stunted, and quality gradually deteriorates. The virus of this disease is mainly transmitted by sap rubbing and by insect vectors such as aphids and mites.
II. Comprehensive control measures
(1) Disinfection of seeds and sowing soil, etc. Seed disinfection can kill pathogens and protect seedlings during the sowing and germination period from infection; if the soil is not disinfected, more than 90% of plants will be infected with root-knot nematode disease after 12 months of cyclamen growth. Therefore, seed and soil disinfection is an important part of cyclamen cultivation.
1. Seed disinfection. For seed disinfection, soak in 10% trisodium phosphate for 20 minutes, or soak in carbendazim or 0.1% copper sulfate solution for half an hour, rinse with clean water, air-dry, and then sow.
2. Disinfection of sowing soil, potting soil, and other materials. When treating large amounts of sowing soil, potting soil, and other materials, chloropicrin fumigation can be used. The method is: pile the soil or potting soil materials into a rectangular heap, make holes in the soil heap at intervals of 30 cm, inject chloropicrin at a rate of 60-160 g per cubic meter of substrate, then quickly cover tightly with two layers of plastic film and fumigate for 15 d. During fumigation, an air temperature of 15°C-30°C gives better results. Then remove the covering, air out the chemical smell, and it can be used; for small amounts, potassium permanganate can also be used to treat the soil. After spraying with 1:1500 potassium permanganate solution, pile it up for 48 hours; piling the soil to no more than 8 cm and exposing it to sunlight also has a certain disinfection effect.
(2) Strengthen cultivation management
1. Pay attention to regulating temperature and humidity. The suitable temperature for cyclamen growth is about 20°C during the day, and about 10°C must be maintained at night. If the temperature is too high, the plants will grow excessively and be prone to disease; if too low, the flowering period will be delayed. If humidity is too high, it can easily cause corm rot. In particular, when the corm is in a waterlogged state for a long time, soft rot is likely to occur.
2. Promptly remove diseased residues, remove diseased leaves and flowers, and disinfect wounds well. Bury diseased residues deeply or burn them to reduce sources of pathogen infection; when removing diseased flowers and leaves, use the thumb and index finger to pinch the middle-lower part of the peduncle and twist left and right so that the base of the peduncle softens and loosens and separates from the mother plant. Never pull hard. After removal, to prevent pathogen invasion, apply 1000-fold carbendazim solution to the plant wounds.
(3) Chemical control. Spraying chemicals or drenching roots in the early stage of onset can greatly improve control efficacy.
1. Bacterial diseases. When bacterial diseases such as soft rot or bacterial leaf rot occur during the growing season, choose 1000-fold streptomycin or Xiaojunling for spraying or root drenching, or use 150-200-fold Bordeaux mixture for spraying.
2. Fungal diseases. For wilt disease, use benomyl 2000-fold solution for root drenching or captan 800-fold solution for spraying; for anthracnose, use carbendazim 800-fold or anthracnose formalin 1000-fold for spraying; for gray mold, use captan 800-fold or benomyl 2000-fold or carbendazim 800-fold for spraying.
3. Viral diseases. When viral diseases occur in plants, chemicals must be sprayed to control the transmission vectors aphids and mites to reduce the chance of other healthy plants being infected with the virus. For aphid control, choose imidacloprid-type chemicals; for mite control, choose avermectin-type chemicals, which have better effects.
4. Root-knot nematode disease. When root-knot nematode disease occurs, fumigation treatment with chloropicrin, methyl bromide, etc. can be used. When nematode disease occurs in potted cyclamen, first wet the pot soil with water, then spread a layer of fine sand about 2 cm thick on the surface of the culture soil. The nematodes in the wet soil drill into the sand to breathe oxygen. Remove the fine sand, repeat twice, and it can be cured. If supplemented with one spraying of 3% formaldehyde, it can be completely eliminated.