The rot of plant roots is called root rot. It was mentioned in the chapter on mushroom mosquitoes that many root rot fungi not only invade the roots of cannabis, but also invade other parts of the cannabis, causing the roots or the whole plant to rot, leading to cannabis. Pathogens that decay overall can also cause root rot in cannabis.
Table of Contents
Different decay conditions of cannabis
The edges of the cannabis leaves are brown and withered
Faded old leaves
New leaves are pale in color
The whole marijuana plant fades
Dark spots
Leaves curl up
Shedding of old leaves
Slow growth
Thin stem
Abnormal growth
Whole marijuana withered
Brown roots
Smelly roots
Root rot
The sprout of the seed germinates and dies
Rot of the seed
The rot of plant roots is called root rot. It was mentioned in the chapter on mushroom mosquitoes that many root rot fungi not only invade the roots of cannabis, but also invade other parts of the cannabis, causing the roots or the whole plant to rot, leading to cannabis. Pathogens that decay overall can also cause root rot in cannabis.
Root rot does not only refer to the root rot of hemp, most of the rot diseases can be classified as root rot.
Today we will focus on root rot and other rot diseases of cannabis.
The marijuana with root rot is the same as the Avadaso curse. It is basically dead. It can survive in rare cases, but even if it survives, it will be deformed or grow too slowly, and lose its cultivation value.
Therefore, the key to preventing root rot lies in prevention rather than treatment.
There are four types of common root rot fungi
Pythium, Fusarium, Rhizoctonia and Phytophthora.
Pythium
Pythium is a highly adaptable fungus. It can infect the roots, root necks, stem bases, leaves and other parts of plants, and can infect all growth stages from seedling stage to growth stage. The earlier the infection time, the more serious the damage.
Symptom
The symptoms of Pythium are complex and require careful identification. The typical symptoms of damping-off caused by the seedling stage are easy to recognize. In drier conditions, root rot caused by Pythium causes slow growth, yellowing, and chronic degradation of diseased plants. The symptoms are difficult to distinguish with the naked eye from symptoms caused by other root rot fungi and certain nematodes. It is necessary to identify the pathogen species indoors. . Leaf rot that occurs under high humidity conditions is easier to identify. When there is dew in the morning, white cotton wool-like mycelium appears between the diseased leaves and the diseased plants, and the appearance is greasy. Place severely infected plants in a place with a higher temperature. After a few hours, they will emit a fishy smell and grow white hyphae.
Pythium is the only pathogenic bacteria that causes decay and death of cannabis seeds, growth retardation and flower bud rot.
Cause
Poor soil drainage and high environmental humidity are the most important pathogenic factors for Pythium. In addition, dense plants, closed land, poor ventilation, high nitrogen fertilizer usage, tender stems and leaves, improper irrigation, tight and heavy soil, and poor drainage will all aggravate the disease. When drying cannabis buds, excessive pursuit of moderate humidity can also cause Pythium infection. High temperature and humidity are conducive to the occurrence of Pythium wilt. When the temperature is 30℃～35℃, the relative humidity of the air is higher than 80% and the high temperature continues, it is most suitable for disease.
Way for spreading
The pathogens are mainly infected plants and oospores. Use water, air, etc. to spread, mainly through the use of broken leaves of diseased plants, wind, running water, shoe soles, and rotten soil to complete the spread.
Prevention method
Pythium is an incurable disease, and the prevention and control methods are mainly based on the prevention and selection of hemp varieties.
Some marijuana varieties are inherently resistant to Pythium, and most of them live in tropical and subtropical varieties.
Prevent decaying plants and the surrounding soil, air, and water from approaching the planting environment, and prevent Pythium oospores from being introduced into the planting environment.
Adjusting the planting environment, keeping the temperature at 20-30 degrees Celsius and humidity below 60% can effectively prevent the growth of Pythium. Prevent excessive watering, keep soil moisture low, and avoid excessive fertilization, especially nitrogen fertilizer.
Strengthen the ventilation of the planting environment to avoid the accumulation of air or anaerobic environment to accelerate the growth of Pythium.
Cannabis is infected with Pythium, mostly seeds, roots and flower buds at the seedling stage. Once the infected part is found, it should be removed immediately, and the Pythium on the plant and in the soil should be killed with a fungicide for fludioxonil. Keep a dry, low-temperature, and ventilated environment to allow the plants to recover. If it cannot be suppressed within 3 days, immediately dispose of the plants and the soil and other facilities where Pythium oospores may be present.
Fusarium
Fusarium is a decomposing fungus in the true sense. Many decays in nature are caused by Fusarium, some cause diseases of wheat, rice and vegetables; some cause fungal diseases of humans and animals, such as corneal ulcers and skin and nail ulcers; some can cause insect diseases. It’s a bit like the one in Nicholas Cage’s “Ghost rider 2” that has the ability to decay and decomposes organic matter, including cellulose and other hard-to-decompose organic matter. It plays a certain role in the natural material cycle. Reaper.
Symptom
Fusarium often infects the vascular system of host plants, destroys the plant’s transport tissue, and produces toxins during plant growth and metabolism to harm crops, causing plants to wilt and die, and affect yield and quality. Fusarium often causes root rot, stem rot, stem base rot, flower rot and many other disease symptoms in plants.
After hemp is infested, it is most obvious on the leaves and stems. Fusarium root rot first affects the root system, and then the disease gradually spreads to the stem. The lower leaves will turn green and yellow at first, and sometimes one side of the plant or half of individual leaves will be infected, and one branch or half of the leaves will be obviously withered and dull; then the symptoms will expand upward, and the upper leaves of the plant will also begin to wilt. Drooping and browning; at this time, the lower leaves begin to fall off, shrink, and finally the whole plant yellows and wilts. When the plant first showed symptoms, it was normal in the morning and evening, and wilted at noon, seeming to be dehydrated. Carefully observe the stem of the plant base, you can see that the epidermis becomes rough with occasional cracks. When the humidity is high, white mold can be seen. Sometimes the mold is pink and gradually turns black. After the disease spot dries up, the base of the plant stem shrinks. . Another obvious feature is that the base of the stem is cut transversely or longitudinally, and there are brown or dark brown ring changes in the vascular bundles. The wilt symptoms caused by Fusarium develop most rapidly and most severely during the high temperature in summer. Fusarium is so destructive that the U.S. government has developed special strains for cannabis and coca as part of the “drug war.”
Cause
Fusarium often accompanies other rot-causing bacteria to invade the plant, or enter the plant through the cut or tender part of the plant. Sometimes the bacteria may be deposited in the vascular system without symptoms, and sometimes it can block the duct immediately after entering the vascular system. Toxic substances are produced, which spread and gradually extend upwards, causing the leaves of diseased plants to wither and die.
The most suitable temperature for the onset of Fusarium wilt is from 27°C to 32°C. At 20°C, the occurrence of the disease tends to be alleviated, and when it is below 15°C, the disease will no longer occur. Cannabis with a large seedling age is more prone to disease than those with a small seedling age. In the spring and summer, if the temperature of the cultivation substrate is high and humid, root damage during potting, transplanting or cultivating will cause disease, and the disease will be severe if the plant growth is weak. Excessive application of nitrogen fertilizers in cultivation and acidic soils are also conducive to the growth and infection of pathogens, and promote the occurrence and prevalence of diseases.
Rotting soil and water are hotbeds for Fusarium bacteria. They enter plants through wounds and tender parts of plants, and kill plants by secreting toxins.
Way for spreading
Fusarium spores spread through the spread of spores. The spores invade the plants through the roots, stem bases and cutting wounds through the flow and splashing of airflow, rainwater, and irrigation water.
Prevention method
Because Fusarium will multiply in the rhizomes of plants, the plants that got Fusarium are dead, and if the plants are infected with Fusarium, they will directly clean the soil water.
To prevent Fusarium, we must first prevent other rotting bacteria or cause physical damage to cannabis, and we should also focus on prevention during the seed and seedling stages.
Keeping the plant temperature below 28 degrees Celsius can effectively prevent the invasion of Fusarium and prevent polluted air and running water from invading the planting environment. Once the spores of Fusarium enter the cannabis cultivation environment, the invasion of Fusarium is inevitable.
Therefore, to prevent Fusarium, we must first prevent other rotting bacteria, and secondly, prevent Fusarium spores from entering the planting environment, especially with regard to water sources. If possible, you can use pure water, and if you don’t, you can use cool white.
Rhizoctonia
Rhizoctonia solani is the main species that causes the rot of cannabis. The disease caused by Rhizoctonia solani is called brown spot. It is a common marijuana rotting fungus.
Symptom
Cannabis seedlings infected by Rhizoctonia solani will show damping-off and developmental arrest.
After an adult cannabis plant is infected by Rhizoctonia solani, the leaves will show signs of over-watering, and white water spots will appear on the leaves, which then evolve into brown and dark brown spots, and finally the leaves turn dark. Brown, then wither and fall.
Cause
When the soil temperature reaches 15.6°C, sclerotia begin to germinate and fungi begin to grow. Like most fungi, the growth of brown spot bacteria is round. It begins to invade plants when the temperature reaches 29°C during the day and 21°C or higher at night. Before invading plants, it feeds on decaying plant organisms on a mat of dead grass.
The occurrence of the disease does not come suddenly. Its development requires a process. The brown spot pathogen can not only invade from the leaves or cuts, but also from the stomata and directly penetrate the leaves. Its invasion of plants is all-round. When the temperature rises, the fungus first infects the roots, then the stems, and finally the leaves.
Way for spreading
The spread of Rhizoctonia solani is mainly by direct invasion of plants and spore dispersal. Similar to the spread of other decomposing bacteria, its spores will also enter the air and invade plants with rain. Its spreading methods are very complete, and it can be said to be the vanguard of all kinds of rotten bacteria.
Prevention method
Keeping low temperature can effectively prevent Rhizoctonia solani from invading plants, and most of the rainwater in the natural environment carries the spores of Rhizoctonia solani. The treatment of Rhizoctonia solani is also mainly prevention. Its invasion method is comprehensive. Fortunately, there are many agents that can eradicate the living bacteria and spores of Rhizoctonia solani.
Phytophthora
Many people think that Phytophthora is a fungus, but its attribution is actually closer to algae, it should be an algae organism. Its habit is similar to other decomposing bacteria, and it is highly dependent on water. As long as there is water, the sporangia or zoospores of Phytophthora will quickly approach the host to find a suitable location, germinate and attack the young tissues of the host plant Secreted and decomposing enzymes quickly disintegrate the host plant tissues to kill the cells, absorb the organic nutrients in them, and quickly multiply more flocculent hyphae and sporangia, which continue to infect.
But unlike other decaying fungi, Phytophthora is an amphibian that can live in pure water and is the main decaying fungus for hydroponic cannabis.
Symptom
The susceptible parts of the disease caused by Phytophthora are often on the young organs or tissues of plants, such as newly germinated buds, seedling stem bases, developing fruits, tender stems, leaves and floral organs. The basic symptom is that the infected part loses water quickly and becomes water-stained, that is, as if it is scalded with boiling water, white flocs will quickly grow on the affected part under high humidity conditions. If the stem base is infected, the stems, leaves and fruits above it will show varying degrees of withering. The more severe the stem base is, the faster the above-ground parts will wither, and even if they remain green, they will fall down and die (damping off). ).
Phytophthora invades the tender parts of plants. It is the main pathogenic bacteria of potato, beans and other crops that feed on rhizomes. It has caused many famines in the world and is the main destroyer of various crops in the world.
Way for spreading
Phytophthora can live on rotting plants, mainly through running water, but also through soil.
Prevention method
Preventing the water source contaminated by Phytophthora from invading the planting environment can effectively eliminate Phytophthora. Soil culture maintains a pH value of 6-7, and hydroponic culture maintains a pH value of 5.5-6. Providing a healthy, ventilated and dry growth environment for plants can prevent Phytophthora from invading plants.
Phytophthora occurs mostly in hydroponic cannabis cultivation, and mostly exists in hydroponic liquid. It is a decaying fungus that hydroponic growers must pay attention to.
I must emphasize here that many foreign farmers have not figured it out.
Light will not harm the roots of marijuana, unless the light is too strong to sunburn all the marijuana. However, there are many discussions that light will harm the roots of cannabis and cause root rot. This statement is biased. In most cases, the roots of cannabis are exposed to the light. This environment will cause the roots to lose moisture, and then the roots will die, giving the rotting bacteria a chance. . In some hydroponic cultivation, the roots of cannabis can also see light, which will accelerate the growth of Phytophthora, strengthen the vitality of Phytophthora, and cause Phytophthora to invade the cannabis plant.
Therefore, light will not kill the roots of cannabis, but it will create opportunities for root-rot fungi.
Recommended drugs:
Methfludioxonil fungicide
Bacillus subtilis fungicide
Mancozeb fungicide
Hymexazol fungicide
Rooting powder (this cannot be sterilized, but watering the soil in advance will make the soil full of beneficial bacteria, increase the difficulty of root rot fungi reproduction, and can effectively prevent various root rot diseases)
Rotation is the lethal killer of marijuana. Prevent it in advance. Don’t let the planting environment be exposed to high temperature and high humidity for a long time. Keep ventilation and keep the planting environment clean and sterile, which can effectively prevent all kinds of rot. Once the marijuana starts to decay, it can be cured, and if it can’t be cured, it should be cleaned up quickly to prevent the spread of decay.
If your planting environment can maintain absolute root-free rot fungi, the plants will never rot even if the temperature and humidity are high.