Control methods of root rot of flowers and plants

Root rot of flowers and plants often occurs in four seasons begonia, African impatiens, petunia and other varieties. As root rot often occurs in summer, it is necessary to prevent flowers before the beginning of summer. The editor will introduce you to the etiology, prevention and treatment of flower root rot.

Begonia semperflorens

1. Etiology

The main pathogens causing root rot are Pythium, Phytophthora, Rhizoctonia sclerotiorum, root black rot and so on. These bacteria can infect plant roots and cause root rot. When 10% of the roots rot, the aboveground can still show a healthy state, but if the environmental conditions are not improved, the rot will further expand; when the decaying roots reach 20% to 30%, the aboveground parts begin to show symptoms, such as chlorosis (similar to deficiency), fallen leaves or leaf necrosis; when the infection extends to the top of the plant, the plant will die quickly.

II. Prevention and control methods

1. Avoid excessive humidity of the substrate, maintain a good drainage environment of the substrate, and disinfect the medium and cultivation environment.

2. Carry out chemical control. Yongning or poisonous alum (oxalaxyl + mancozeb) 600x to 800x liquid spray, 1000 times liquid to root irrigation; Suzhining (metalaxyl + mancozeb) 600x to 800x liquid spray, 800x to 1000 times liquid spray; Minjia (ethylphosphine aluminum) 600x liquid spray, 200x to 500x liquid spray; Prike (aldicarb) 800x to 1000 times liquid spray, 1000 times liquid to root irrigation.

The above several agents have protective and therapeutic effects, and can be used before or in the early stage of the disease. They can be used regularly for 7 to 10 days, and the effect of root irrigation is better.

The prevention and control of root rot of succulent plants is really "worm has root powder, disease has Fusarium oxysporum" and "black rot" is no less capable of causing panic than "root powder". The results of sampling diseased plants by foreign meat growers mentioned a fungus: Fusarium oxysporum. Fusarium oxysporum (F.oxysporum) is a worldwide soil-borne pathogenic fungus with a wide range of hosts, which can cause Fusarium wilt of more than 100 species of plants, such as melons, Solanaceae, bananas, cotton, legumes and flowers. Fusarium oxysporum is a semi-known fungus (Imperfecti fungi), cultured from Moniliales, Tuberculariaceae and Fusarium on PDA counter-insurgency. The colony is flocculent and the hyphae are white and dense. The colony is pink-white, light pink to fleshy, purplish and powdery due to the production of a large number of spores. Colony high 3~5mm, small conidia born on the solitary bottle pedicel, often agglomerated at the top of the bottle stalk, unicellular, ovate; large conidia sickle-shaped, a little curved, mostly 3-septum. Chlamydospores apical or terminal, globose. Fusarium wilt pathogen can produce three types of conidia: small conidia, large conidia and chlamydospores under natural or artificial culture conditions. Small conidia are colorless, unicellular, oval, kidney-shaped, long pseudocapital, 5~12um × 2~3.5um in size. The large conidia are colorless, multicellular, sickle-shaped, slightly curved, with slightly pointed cells at both ends, the size of 19.6~39.4um × 3.5~5.0um. Chlamydospores are yellowish, nearly spherical, smooth, thick, mesophytic or terminal, solitary or tandem, and have strong resistance to adverse environment. Fusarium wilt is one of the important diseases of ornamental flowers, which can infect many kinds of flowers, such as lily, Cymbidium, Phalaenopsis, cyclamen, poinsettia, African chrysanthemum, chrysanthemum, Platycodon grandiflorum, carnation and so on. Once the plant is susceptible, if the control measures are not timely, it will lead to the rapid spread of the disease. Fusarium often causes many diseases such as root rot, stem rot, stem rot, flower rot and so on, and more than 100 host plants are infected. Fusarium often infects the vascular bundle system of host plants, destroys plant transport tissues, and produces toxins in the process of plant growth, development and metabolism to harm crops, resulting in plant wilting and death, affecting yield and quality. The disease is one of the important diseases which are difficult to control in the production of ornamental flowers. Fusarium wilt is one of the important diseases of ornamental flowers, which can infect many kinds of flowers, such as lily, Cymbidium, Phalaenopsis, cyclamen, poinsettia, African chrysanthemum, chrysanthemum, Platycodon grandiflorum, carnation and so on. Once the plant is susceptible, if the control measures are not timely, it will lead to the rapid spread of the disease. Fusarium often causes many diseases such as root rot, stem rot, stem rot, flower rot and so on, and more than 100 host plants are infected. Fusarium often infects the vascular bundle system of host plants, destroys plant transport tissues, and produces toxins in the process of plant growth, development and metabolism to harm crops, resulting in plant wilting and death, affecting yield and quality. The disease is one of the important diseases which are difficult to control in the production of ornamental flowers. Symptom recognition different ornamental flowers show different symptoms after being infected by Fusarium oxysporum. For example, after the grass flowers and cut flowers born in 2012 are infected, the lower leaves will first lose green and yellowing, and sometimes one side or half of individual leaves will be infected, it will show that one side of the branches and leaves or half of the leaves are obviously withered and dull; then the symptoms expand upward, and the leaves of the upper plants begin to wilt and droop and turn brown. At this time, the lower leaves began to fall off, wrinkled, and finally the whole plant yellowed and withered. When the plant first showed symptoms, it was normal in the morning and evening, wilted at noon, like a lack of water. Careful observation of the stem at the base of the plant shows that the epidermis becomes rough and occasionally cracked, white mildew can be seen when the humidity is high, and sometimes the mildew is pink. For some high-grade potted flowers, such as Phalaenopsis, Cymbidium and Anthurium andraeanum, after infection with Fusarium, in addition to etiolation, red-purple and shedding of the leaves, water-immersed disease spots can also be seen at the base of the stem and gradually turn black. After the disease spot dried up, the stem base of the plant was shrunk. Another obvious feature of plants infected by Fusarium oxysporum is that the vascular bundles are brown or dark brown when the stem base is cut cross or longitudinally. The wilt symptoms caused by Fusarium oxysporum develop most rapidly and seriously at high temperatures in summer. The pathogen of Fusarium wilt is Fusarium oxysporum (Fusariumspp.), which belongs to semi-knowns subphylum fungi. It is not only the pathogen causing vascular bundle diseases of ornamental plants, but also a kind of fungi distributed all over the world, widely distributed in soil, animal and plant organisms, even in the cold Arctic and arid hot deserts. It belongs to parasitic or saprophytic life. It can not only survive winter and summer in soil, but also show different specialization types in different ornamental plants. The pathogen generally produces conidia, and there are two types of conidia, namely large conidia and small conidia. The large conidia are stout, scattered on aerial hyphae or in conidia, myxospores and slippery layers. Large conidia have various shapes, slightly curved, such as sickle-shaped, orange petal-shaped, spindle-shaped, mallet-shaped, etc., with a slightly pointed tip and thin spore wall. Most of the large conidia are separated by 3 to 10, and some are more separated. The diaphragm is also different, some separation is obvious, and some separation is not obvious. The morphology of spores produced on conidia is more typical and stable than that on aerial hyphae. The small conidia are small, mostly unicellular, a few are 1-3 septate, ovate, reniform to rectangular round, etc. When the environment is unfavorable, the dying plant tissue and the diseased body in the soil can produce a large number of chlamydospore, which is a small, round thick-walled spore. The pathogen of Fusarium wilt overwintered as mycelium or chlamydospore in soil or culture medium or attached to seeds, which can lead saprophytic life. The rot of the root or stem of the diseased plant produces fruiting body in a humid environment, and the spores are spread by the splashing of airflow, Rain Water and irrigation water, and invade through the wounds of young roots and stems or cutting seedlings. Sometimes the pathogen may be deposited in the vascular bundle system without symptoms, and sometimes it can block the catheter immediately after entering the vascular bundle system, and produce toxic substances, which spread and gradually spread upward, causing the leaves of the diseased plants to turn yellow and die. The study on the spread of bacteria in the host shows that the spread of bacteria in the vascular bundle is relatively slow before the appearance of symptoms, but there may be hidden Fusarium pathogens when some reproductive materials are obtained from diseased plants. Therefore, the reproductive material is an important source of Fusarium wilt disease transmission, and the contaminated soil or substrate is also one of the sources of disease transmission. The most suitable temperature for the onset of Fusarium wilt was from 27 ℃ to 32 ℃. The disease tended to ease at 20 ℃ and stopped at less than 15 ℃. Ornamental plants with older seedlings are more susceptible to disease than those with younger seedlings. In spring and summer, if the temperature of the cultivation substrate is high and wet, the root system will be damaged more when changing pots, transplanting or ploughing, and the disease will be serious if the plant growth is weak. Excessive application of nitrogen fertilizer and slightly acidic soil in cultivation are also conducive to the growth and infection of bacteria and promote the occurrence and prevalence of diseases. Fusarium wilt often occurs in South China from April to June, while Fusarium wilt in Yunnan, Sichuan and East China occurs from May to August. [PS: that's right. My dozens of brilliant heads have recently gone to recruit immortals. The methods of prevention and treatment in the early stage and later stage of the disease. Select the excellent varieties which are suitable for intensive cultivation and disease resistance. two。 Cut flowers and 2012 grass flowers should be cultivated in rotation to prevent the accumulation of pathogens caused by continuous cropping. 3. Disinfect the soil and cultivation substrate, and the diseased plants found in cultivation should be pulled out and destroyed in time to reduce the further spread of bacteria. 4. In order to master the plant planting density, strengthen ventilation, reduce humidity and control the water content of soil or substrate, it is appropriate to choose the substrate with good drainage. 5. Chemical control: 3000 to 5000 times of Amisi or 4000 to 5000 times of Medallion, thiabendazim or carbendazim can be used to treat roots and stem bases before planting cuttings. After planting, transplanting or changing pots, 3000 to 5000 times of Amicida or 4000 to 5000 times of Medallion were used to irrigate roots once. In the middle and later stages of plant vegetative growth, the harm of Fusarium wilt could be effectively prevented by using 3000 to 5000 times of Amicida and 4000 to 5000 times of Medallion to irrigate roots for 2 to 3 times every 14 to 21 days. Note: Medallion is a contact protective fungicide, which acts by inhibiting the transfer related to glucose phosphorylation to inhibit the growth of pathogenic mycelium and eventually lead to the death of bacteria. Prevention and Control of Root Rot of Flower seedlings

There are a variety of pathogens that can cause root rot of flower crops and cause serious losses to flower production. These pathogens can cause flower seedlings in the medium to die before or after emergence, or cause chronic or acute root rot to mature plants. Unlike rust and Botrytis cinerea with specific hosts, these root rot pathogens usually infect a wide range of plant species.

The root rot of flower production in greenhouse is mainly caused by four kinds of fungi and some bacteria. That is, Pythium, Phytophthora, Sclerotinia sclerotiorum, Candida albicans and bacteria and so on. According to different pathogens, the methods of agricultural control and chemical control are also different, so it is very important to judge which kind of fungi caused the harm.

1. Pythium

It exists widely in unsterilized soil, and may also exist in washed fine sand and some peat media. Pythium is closely related to water because the zoospores they produce are spread or swim through water. Although these pathogens are not strong competitors compared with other pathogens in the soil, they can survive in the soil for many years through spherical, thick-walled resting spores (oospores). These oospores are also commonly found in diseased tissues, and examination of these oospores can be used to identify pathogens.

The root rot caused by Pythium usually occurs in the cultivation container with high water content, poor drainage and unsuitable temperature. Excessive application of nitrogen fertilizer can cause germs to multiply and grow rapidly. Plants affected by Pythium that produce root rot often show growth hindrance or even wilting. The leaves were gray, even yellowing, similar to nitrogen deficiency. Almost all crops show symptoms of discoloration after the occurrence of rotten root rot, usually starting from the small lateral root or root tip, resulting in light brown damage to the root, causing the outer layer of the root to rot, leaving only the inner pith of the very thin root. With further development, the roots become dark brown or even black, and are soaked with water. If you rinse the roots gently, the rotting roots can be washed away easily.

Pythium can also be found in soilless medium, and both heated and sterilized soil and soilless medium can be easily infected with Pythium.

The main routes of transmission are:

Use unclean tools, flowerpots, etc.; people or pets walk on mixed media; dump mixed media on uncleaned planting beds or upper basin areas; some flying insects can also cause Pythium to spread from greenhouse to greenhouse.

When the soil is disinfected, if the disinfection time is too long or the temperature is too high, then once the soil is infected with Pythium, it will cause more serious root rot, because the Pythium has few "natural enemies".

Once the roots begin to rot, Pythium is difficult to control, so prevention must be given priority to. The measure is to first heat the soil to 82 ℃ and keep it at that temperature for 30 minutes, which will kill the beneficial organisms in the substrate for too long or too high a temperature, then cover and store the sterilized soil and prevent it from coming into contact with the unsterilized soil. Special attention should also be paid to the storage of soilless media for commercial use.

If you use reservoir water or running water for irrigation, it should be noted that the inlet pipe should not be placed too deep to prevent the lower sediment from being sucked into the pipe. If irrigation water is contaminated by Pythium, it should be disinfected before use. The reservoir of the ebb tide irrigation system should be covered to prevent plant debris from entering. In addition, the backwater is filtered to remove soil and plant debris from the water and protect the reservoir from Pythium pollution.

Disinfect seedbeds, pots, tools and utensils that may come into contact with implant substrates. And regularly carry out comprehensive and thorough disinfection of the reservoir of the ebb tide irrigation system. For greenhouses with a history of rot mold, the greenhouse should be disinfected at the initial stage of planting as soon as possible. Biological agents can be added to the planting medium before, during or after seedling transfer, and can even be used to deal with burrow-plate seedlings directly before transplanting seedlings. However, do not use chemical pesticides within 10 days before and after the use of biological fungicides.

In order to achieve the desired prevention effect, biological agents and fungicides may need to be used many times. Some Pythium can also develop resistance. When some chemical insecticides are not effective, you can switch to other products.

two。 Phytophthora

Phytophthora is also widely found in unsterilized soil, and may also exist in washed fine sand and some peat medium. it is an amphibious fungus, facultative parasitic or saprophytic, and most of them are facultative parasites. The high humidity environment is beneficial to the growth and reproduction of Phytophthora, and its sporangia and zoospores can be transmitted by wind, rain, infected seedlings, soil and irrigation water. After the pathogen invades the host plant, it can produce a large number of sporangia and release zoospores for further re-infection. under the appropriate temperature and humidity, the number of bacteria increases rapidly, leading to the epidemic of the disease in a very short time. Root rot caused by Phytophthora also usually occurs in the case of high water content and poor drainage.

3. Rhizoctonia

Most potted flowers are susceptible to root rot caused by Rhizoctonia. The pathogen is widely found in soils that have not been steam sterilized or medically fumigated. This pathogen can be easily identified by a microscope because its hyphae branch at a typical right angle. Although it cannot produce airborne spores or zoospores, Rhizoctonia can produce a hard dormant structure called hardened spores that can survive in plant remains or soil for many years.

Rhizoctonia can easily spread from one place to another through flowerpots or other equipment. Rhizoctonia can cause damage to roots, rhizomes and even aboveground parts. Initially, the root of the disease developed discontinuously, resulting in light brown to dark brown plaques. With the development of the disease, the disease spots are connected together, resulting in root rot and death. Unlike the root rot caused by Pythium and Phytophthora, Rhizoctonia root rot does not show the characteristic of rotting root system soaked with water. After the root system is infected, the pathogen will further infect upward, causing rhizome rot or stem rot, and often form longitudinal cracks in the diseased tissue.