Methods for preventing and treating root rot disease in succulents
Compared to the knowledge most people have about succulents, the methods for preventing and treating root rot disease in succulents, let's follow the editor to see the specific content!
It's really not inferior to "root meal" in terms of causing panic, right? "Black rot" caused by "root meal" and "Fusarium oxysporum"? The results of the inspection of diseased plants sampled and sent for testing by foreign masters growing succulents mentioned a type of fungus: Fusarium oxysporum.
Fusarium oxysporum is a worldwide distributed soil-borne pathogenic fungus with a wide range of hosts, which can cause wilt disease in more than 100 plant species, including cucurbits, solanaceous vegetables, bananas, cotton, legumes, and ornamental plants. Fusarium oxysporum belongs to the category of imperfect fungi (Moniliales), Tuberculariaceae, and Fusarium genus. Cultured on PDA plates, the colony is fluffy and the mycelium is white and dense. The colony is pinkish white to flesh-colored, slightly purple, and powdery due to the generation of a large number of spores. The colony is 3-5 mm high, with small conidia born on single phialides, usually clustering at the top of the phialides, single-celled, and ovoid; large conidia are sickle-shaped, slightly curved, and mostly 3-septate. Chlamydospores are apical or terminal, spherical. Fusarium wilt pathogen can produce three types of spores: small conidia, large conidia, and chlamydospores under natural or artificial culture conditions. Small conidia are colorless, single-celled, ovoid, kidney-shaped, etc., and have a long peduncle, measuring 5-12 μm × 2-3.5 μm. Large conidia are colorless, multi-celled, sickle-shaped, slightly curved, with pointed ends, measuring 19.6-39.4 μm × 3.5-5.0 μm. Chlamydospores are light yellow, nearly spherical, smooth-surfaced, thick-walled, intercalary or terminal, single or in chains, and resistant to adverse environments.
----------------------------------------------------------
Fusarium Wilt
Fusarium wilt is one of the important diseases of ornamental flowers, which can infect lilies, large cattleyas, orchids, cyclamen, poinsettias, African daisies, chrysanthemums, lisianthus, carnations, and many other flowers. Once a plant is infected, if control measures are not taken in time, the disease will spread rapidly. Fusarium wilt often causes root rot, stem rot, stem base rot, and flower rot in plants, infecting more than 100 host plants. Fusarium frequently infects the vascular bundle system of host plants, destroys the plant's conductive tissue, and produces toxins during the plant's growth and metabolic process to harm crops, causing plant wilting and death, affecting yield and quality. This disease is one of the most difficult to control in ornamental flower production.
Symptom Identification
Different ornamental flowers show different symptoms after being infected by Fusarium. For example, when biennial or annual herbaceous flowers and cut flowers are infected, their lower leaves will first turn yellow and lose green, sometimes one side or half of a leaf is infected, showing obvious wilt and lack of luster on one side of the branch or half of the leaf; then the symptoms spread upwards, and the upper leaves of the plant also begin to wilt and droop, turning brown; at this time, the lower leaves start to fall off, wrinkle, and finally, the whole plant turns yellow and wilts. When the plant first shows symptoms, it is normal in the morning and evening, but wilts at noon, resembling a water deficit. Upon close observation, the stem base of the plant can be seen to have rough skin, with occasional cracks, and white mold can be seen in high humidity, sometimes pink mold.
For some high-end potted flowers, such as orchids, large cattleyas, and red掌, after being infected with Fusarium, besides yellowing, redness, and leaf drop, water-soaked lesions can be seen at the stem base, which gradually turn black, and the lesions dry up, causing the stem base to shrink. Another obvious feature of plants infected with Fusarium is that when the stem base is cut transversely or longitudinally, a brown or blackish-brown ring can be seen in the vascular bundle. Fusarium wilt symptoms develop most rapidly and severely in high summer temperatures.
Pathogen
The pathogen of wilt disease is Fusarium spp., belonging to the Deuteromycetes. It is a specific pathogen causing vascular bundle diseases in ornamental plants; it is also a type of fungus with worldwide distribution, widely found in soil and the organic matter of animals and plants, even in the cold Arctic and hot deserts, and is considered an obligate or facultative parasite. It can not only overwinter and overheat in the soil but also show different specialization types on different ornamental plants.
The fungus usually produces conidial seats, and conidia are of two types: large conidia and small conidia. Large conidia are robust, scattered on aerial mycelium or on conidial seats, mucilage masses, and mucilaginous layers. Large conidia are diverse in shape, slightly curved, and can be sickle-shaped, lobed, spindle-shaped, or club-shaped, with slightly pointed ends and thin spore walls. Large conidia usually have 3 to 10 septa, some even more. The septa are also different, with some distinct and others indistinct. Spores produced on conidial seats are more typical and stable than those on aerial mycelium. Small conidia are smaller, mostly single-celled, a few with 1 to 3 septa, and are ovoid, reniform, to rectangular.
When the environment is unfavorable, a large number of chlamydospores can be produced in the dying plant tissue and soil debris.
Incidence Patterns and Transmission Routes
The Fusarium wilt pathogen overwinters as mycelium or chlamydospores in the soil, growing medium, or attached to seeds, and can live as a saprophyte. The decaying roots or stems of diseased plants produce fruit bodies in a humid environment, and spores are spread by air currents, rainwater, or splashing irrigation water, infecting through the wounds of young roots and stem bases or cuttings. Sometimes the fungus may exist in the vascular bundle system without symptoms, and sometimes it can immediately block the xylem vessels and produce toxic substances, spreading upwards and gradually causing the leaves of the infected plants to turn yellow and die.
Research on the expansion of the pathogen within the host plant shows that before symptoms appear, the expansion of the pathogen within the vascular bundle is relatively slow, but there may be hidden Fusarium pathogens when part of the propagation material is obtained from infected plants. Therefore, propagation material is an important source of Fusarium wilt disease transmission, as is contaminated soil or growing medium.
The optimal temperature for the occurrence of Fusarium wilt is between 27°C and 32°C, the disease tends to be mild at 20°C, and it does not occur below 15°C. Older plants are more likely to be affected than younger ones. In spring and summer, if the temperature of the growing medium is high and humid, and the roots are injured during potting, transplanting, or hoeing, the plants are more likely to be affected. The excessive application of nitrogenous fertilizers and acidic soil also favor the growth and infection of the pathogen and promote the occurrence and spread of the disease. In South China, wilt disease often occurs from April to June, while in Yunnan, Sichuan, and East China, it often occurs from May to August.
Control Methods at the Early and Late Stages of the Disease
1. Choose suitable elite varieties that are resistant to the disease.
2. Rotate the cultivation of cut flowers and biennial or annual herbaceous flowers to prevent the accumulation of pathogens due to continuous cropping.
3. Disinfect the soil and growing medium; if a diseased plant is found during cultivation, it should be removed and destroyed in time to reduce the further spread of the pathogen.
4. Master the planting density of the plants, enhance ventilation, reduce humidity, and control the water content of the soil or growing medium, and use a well-drained medium.
5. Chemical control: Use Amistar 3000 to 5000 times or Medallion 4000 to 5000 times, thiabendazole or carbendazim 500 to 600 times liquid to treat roots and stems before planting or cutting. Use Amistar 3000 to 5000 times or Medallion 4000 to 5000 times for root irrigation after planting, transplanting, or repotting. Use Amistar 3000 to 5000 times and Medallion 4000 to 5000 times alternately for root irrigation 2 to 3 times every 14 to 21 days during the middle and late stages of plant growth to effectively prevent and control the harm caused by Fusarium wilt.
Note: Medallion is a contact protective fungicide that works by inhibiting glucose phosphorylation-related transfers, thereby inhibiting the growth of the pathogen mycelium, ultimately leading to the death of the pathogen.
The above is the specific content of the methods for preventing and treating root rot disease in succulents (figure), if it can bring you help, remember to visit the website often!