Spotting and Treating Fusarium Fungus

marijuana plants growing tall in a field

Like any other plant, cannabis can be affected by a number of pests and diseases. Growers take painstaking efforts to prevent these biological infestations from taking over their entire marijuana crop. Plant diseases, in particular, stem from bacteria, fungi, and viruses that can be difficult to identify and control. Fungi, however, are the most common threat to marijuana plants. While some fungi are good, fusarium on marijuana plants can be devastating.



A range of environmental conditions including pests and substandard growing facilities can be a breeding ground for harmful fungi. And fusarium on marijuana plants is one of the most common fungal infections that can wipe out plants nearby, if left untreated.

What Is Fusarium?

marijuana plant growing with buds

Fusarium is a soil-borne fungi that mainly affects plants consumed by humans. This plant pathogen has been known to target tomatoes, potatoes, eggplants, peppers, and other vegetables and fruits. Fusarium can also affect decorative flowers like sunflowers, carnations, lilies, and petunias. In fact, fusarium is so efficient at devastating crops that the United States government has used it as a biological weapon against cocoa plants in South America as part of their "War on Drugs."

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There are many species and varieties of fusarium that can remain active on contaminated soil indefinitely. These pathogens lay dormant, feeding on decay and decomposition of nearby organisms. The fusarium fungus flourishes in soil and air that exceeds 80 degrees Fahrenheit. It produces spores that can become airborne in areas with extremely dry weather. Fusarium produces toxins in the roots causing the plant's cells to decay and eventually disintegrate. The mycotoxins fusarium produces are harmful to people, especially people with weak immune systems.

Fusarium on marijuana plants affects the xylem system, marijuana's vascular system, to block the absorption of nutrients and water. These fungi colonies can range in color from light to bright, depending on the species of fusarium. Varying species of fusarium cause different symptoms like wilting and root rot. Fusarium spores can be spread by running water, contaminated tools, bugs, and dry heat.

What Are Symptoms Of Fusarium On Marijuana Plants?

dead, copper colored leaves because of fusarium on tomato plant

Fusarium on marijuana plants is extremely difficult to detect before it's wiped out your marijuana plants. Since this fungi is soil-borne, all of the action occurs under the ground. Growers visually inspect plants regularly to identify the many symptoms of disease infestation, especially fusarium infestation. Because fusarium blocks the absorption of nutrients and water, plants quickly exhibit signs of decay and decomposition. The disease spreads up the plant to the stems, leaves, and flowers.

One symptom to look out for is tiny dark spots on leaves. Leaves that were once a vivid green hue turn a dreary brownish-yellow color. Because of the stress on the plant, leaves can begin to wilt and curl at their tips, and sometimes fall off. Other symptoms include stems that bust wide open revealing a rusty red color signifying root rot. Since root rot isn't visually accessible, you won't find out until it's too late. Fusarium spreads beginning at the root system destroying the cells that help the plant get nutrients and water. Without sustenance, the marijuana plant is no longer able to support itself and it collapses.

How To Remove Fusarium On Marijuana Plants

close up high quality marijuana seeds to keep out fusarium on marijuana plants

Whether you have an outdoor or indoor growing environment, prevention is key when dealing with fusarium on marijuana plants. Once affected, however, growers resign themselves to the lethal fungi and safely dispose of their affected plant and start fresh. Infected plants are separated from the pack in order to stop the disease from spreading to nearby cannabis plants. One of the most important methods of fusarium prevention is buying high-quality seeds from trusted sources with genetics that have been proven to ward off common pests and diseases.

Organic Soil

holding healthy soil

Maintaining healthy soil is vital in preventing fusarium on marijuana plants. Not all fungi threaten marijuana plants. For example, natural fungicides like nettle and horsetail are full of nutrients, minerals, alkaloids, and silica. Silica, especially, helps plants resist against diseases by strengthening cell walls, making it difficult for pathogens to break it. Growers also use compost tea to introduce microorganisms to make marijuana plants more resilient against diseases.

Introducing molasses to the soil feeds microorganisms that can aid in growing a healthy plant. Additionally, clay soil has been used to increase the pH of the soil, which can reduce the chance of fusarium on marijuana plants. Loam soil (clay, silt, sand) also works by putting microbes into the soil to get rid of fusarium. Mycorrhizae and trichoderma, specifically, are beneficial fungi that builds up a plant's resistance to pathogens.

Water and Fertilizer

marijuana plant in a pot

Fusarium can also thrive in overly moist environments. Too much water can reduce the amount of oxygen in the soil. Lack of oxygen is a breeding ground for fusarium on marijuana plants. Some growers suggest that an inch of the top of the soil should be completely dry before watering again. Running water can spread fusarium across other plants if they're nearby. Over-fertilization with nitrogen and phosphorus can provide the ideal environment for fusarium.

Outdoor vs. Indoor Growing

indoor marijuana grow house, a good way to not get fusarium on marijuana plants

When growing marijuana plants outdoors, use containers that aren't planted in the ground in order to reduce the surface area that can get infected. This also prevents fusarium from reaching other plants, ideally. Indoor growing has shown the most promise because humidity and temperature levels are easier to control. Fusarium thrives in tropical, warm, and moist climates. Hydroponic growing and using a hygrometer can help you measure humidity levels. When it gets too humid, dehumidifiers can restore appropriate levels.

Tool Sterilization

gardening tools on green grass, sterilizing tools is a good way to prevent fusarium on marijuana plants

Fusarium can travel from one plant to another if a tool comes in contact with the fungi. Tools may include garden gloves, hoses, boots, and other growing necessities. These tools should be sterilized to prevent fusarium infestations. Hydrogen peroxide can be used as a disinfectant. Hydrogen peroxide can also be added to the soil for sterilization. The exact amount varies but is generally around 20 cc of hydrogen peroxide per liter of water used.

Pests and diseases can easily affect an entire crop when grown outdoors, not only destroying the yield, but affecting a grower's livelihood. Fusarium on marijuana plants has been a pain for growers, but innovative techniques are proving effective to beating this ubiquitous fungi.

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