Fusarium on marijuana plants

Fusarium is a type of fungi that specifically targets the leaves and roots of the marijuana plants. Dormant in warm, tropical soil, it can wait for years for the perfect time to hit the crop. Hence, it can be present anywhere in the garden. In addition, it is often spread by running water and garden tools.

For many soil growers, fusarium poses an immense threat when activated as it causes wilting or root rot depending on the strain of weed. The worst thing is that once the infestation starts, it can be extremely hard to treat affected plants. For many growers, dealing with it can be very tricky.

Since fusarium dwells and thrives only in soil, growing hydroponically is a good option to avoid it. However, this setup might not be viable for many growers. Fortunately, there are steps we can take to ensure that the fungi don’t touch our soil-grown crop.

How to get rid of fusarium in marijuana plants

Hence, this article will teach the skills to prevent it from causing harm in the first place. This includes being able to spot it as soon as the first sign of infection shows.

For the most part, ensuring a fusarium-free weed garden means working hard to make the environment less welcoming to the fungi. So, read on to start learning how to stop fusarium from ruining the chance to get a decent harvest.

Download my free Grow bible to learn more about fusarium and other diseases in marijuana plants.

How to remove fusarium from the cannabis garden

Fusarium is one of the hardest problems in the marijuana garden to fix. But once we learn the basics, we can do something to stop it. Here are some surefire ways to dealing with this soil fungi.

Prevent it

As mentioned, it’s hard to save the plants once fusarium strikes. While there are some things we can do to minimize the damage, it makes more sense to simply throw away the affected plants and start anew. Hence, the top priority when dealing with it is prevention. In this section, we will learn the steps to do this.

Start with high-quality seeds

Start with High-Quality seeds

Using the correct nutrients and plant protector will get you a long way and your plants will have less chance of getting sick, in addition of being less vulnerable for pests and diseases. I have created multiple grow sets which features all you need in order to grow healthy plants from seed to harvest!

buy white widow marijuana grow set

Buy your grow set

Use good soil

Since Fusarium thrives in soil, protect marijuana plants by starting with a fusarium-free medium. This includes using natural fungicides from preparations of nettle and horsetail. We can also use compost or compost tea to increase the beneficial bacteria that remove bad fungi.

To nourish the soil, add bacterial food like molasses to support the good bacteria within the soil. If clay soil is available, use it to increase the pH of the medium which lowers the number of the fungi.

Use good loamy soils

Loamy soils are also helpful since they might be housing microbes that fight off fusarium. Planting other healthy plants together with the cannabis also improves the quality of the soil and help control the problem.

To further ensure the safety of the soil, use containers instead of planting directly on the ground. This limits the area of infection which makes it easier to limit the spread of infection.

Grow indoors

As with any fungi, fusarium develops in moist and warm environments. So, we have a better chance of preventing its growth if we can manually adjust the humidity and temperature. And the best way to do this is to grow the plants indoors where we can monitor and modify many variables.

Grow marijuana indoors

In this type of setup, growers can pay close attention to the humidity levels by using a hygrometer. If the reading is too high, which sometimes happens, use dehumidifiers to restore it to the correct levels. Since plants require less moisture over time, make sure to monitor the grow room regularly.

Sterilize garden tools

Sterilize Garden Tools

Diseases are often spread from one place to another by using garden tools that have come in contact with the fungi. So, make sure to clean and sterilize this equipment as well as the gardening gloves and the watering hose. When it comes to stopping fusarium, we need to cover all the bases.

Avoid overwatering

Avoid overwatering marijuana plant

Aside from cutting out the oxygen supply in the roots, overwatering also promotes the growth of any fungi.

Also read When Is the best time to water weed plants?

So, learn the correct ways to water the plants to avoid these common problems.

Correct Nutrients

If you want to make sure that you give you plants the highest chance on getting the proper nutrients, or to prevent nutrient issues in in the first place, I have created a perfectly balanced fertilizer kit, ready to use for all marijuana plants!

buy marijuana fertilizer set

Bergman’s fertilizer kit

  • Enough nutrients for at least 5 plants
  • All the nutrients from seedling to harvest
  • Usable for all marijuana plants
  • Suitable for soil, hydroponic and other growing mediums

Look for signs of infection

Monitoring the status of the marijuana plants is a big part of taking care of them. Without it, we won’t be able to know if our plants are suffering from a Fusarium infestation. But what does an infected plant look like? As mentioned, the two main symptoms are wilting and root rot depending on the type of the weed.

Leaf symptoms

Marijuana leaf symptoms fusarium

A fusarium attack will quickly wilt the leaves, changing it from vibrant green to yellow and brown. But the sure sign of a Fusarium wilt is when the tips curl upwards while the leaves look as though they may drop off but actually won’t’.

Root symptom

It’s a little bit harder to detect the initial signs of a fusarium root rot which is when the roots turn reddish. Obviously, we can’t see this as the roots are buried underground. But the fungus is already working to block water and nutrients from getting into the plant.

Root Symptom

As the symptom worsens, it starts to move up fast into the stems and rot them as well. As a result, the plant will collapse and die.

Stop the infection

While it may be futile to treat infected plants, we can try to save the healthy ones if we move fast. In general, it’s way easier and safer to just start again. So, here’s how to do it.

Act fast

It’s important to remove the affected plants right away as soon as we notice the symptoms. If we don’t do this, it will decompose and serve as a breeding ground for the fungi.

Act Fast

As a result, any plant that will grow in the same soil will also be devastated.

Add hydrogen peroxide

Add Hydrogen Peroxide

After getting rid of the infected plant, apply hydrogen peroxide to the soil to disinfect it. This will also add oxygen to the soil which will improve its quality. To use, add 20cc of hydrogen peroxide per liter of water to achieve these desired effects.

Know how to perfectly time your harvest so you can maximize your yield. Download our free mini harvesting guide

Start anew

As mentioned, it’s hard to save the plants once fusarium strikes. While there are some things we can do to minimize the damage, it makes more sense to simply throw away the affected plants and start again. This is to ensure that we don’t smoke infected buds as they can be harmful to our health.

Start Anew

To begin planting, pick a location that is as far away from the infested site as possible. Indoors, we can achieve the same effect by cleaning the grow space and using a different soil.

It is always best to make sure that you give diseases or pest not even the slightest chance to find a place to stay among your plants. To prevent these issues, I have created a pack of three bottles which contents will make sure your plants get the best protection possible!

Marijuana plant protector

Bergman’s Plant Protector

  • Protect your plants from diseases and harmful pests.
  • Consists of three 20 ml bottles
  • Enough plant protection system supplies for up to 20 plants
  • Suitable for soil, hydroponic and all other grow mediums

Maintain healthy soil to beat fusarium

Prevention is key when it comes to dealing with Fusarium in the marijuana garden. As such, it’s best to grow indoors and provide only enough water and use the correct intensity of light. This will create an environment that is not friendly to the fungi.

But when we do notice the problem, it’s best to simply throw away the plant and start all over again. This will reduce the spread of Fusarium infection and ensure that we only get healthy buds.

Happy growing!


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Mr Robert Bergman PhD


Robert Bergman is an Amsterdam-based marijuana grow expert who has years of experience from small grows to massive operations ... See profile

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17 comments on “Fusarium on marijuana plants”

  1. The only way to beat fusarium is to prevent fusarium. Hydroponics growers should be good if using good sanitary practices and have good source water. Outdoor growers have options. Using a broad spectrum fungicide and attempting to kill everything will create a biological vacuum which will enable fusarium, Pythium and other soil borne pathogens to rapidly colonize the soil and infect your plants. Better to enhance soil biome. There are ways to induce bacteria and fungi in your soil to produce enzymes that will kill pathogens. Growing in containers is good advice, but use a well drained media, like coco or vermiculite, and water lightly, but frequently–several times a day depending upon pot and plant size and weather. You can hardly overwater in a well designed potting media. Give it a hydro solution on drip. Humidity has nothing to do with fusarium infections. I would lay down a nursery fabric under pots to minimize contact between pot and soil. Five gallon containers with two drippers should be fine., Solarizing the soil between crops can help. Not so long ago, nurseries would have steam lines running through the beds within their greenhouses. Steam will kill everything. Pasturizers are better. They can regulate temperature in pipes to keep soil between 150 F and 180 F. This will kill pathogens but leave the beneficial organisms.

  2. {atrick,

    Mycorrhiza fubgi does is necessary, and I would suggest that you research Lacto Bacillus (LABS”

    Happy growing

  3. Grower,

    Fungus can spread and I am not surprised by your claim. I believe Hydroponic was overlooked due to small % of plants affected. Wouldn’t you agree. This article is more about recognizing fusarium wilt, and not necessarily where else it may spread aside from soil.

    Thanks. Happy growing.

  4. Any instances of fusarium in hydroponic production? Drip or DWC? This article claims no fusarium outside soil-based cultivation, however I have first hand experience with plant pathology tests proving otherwise.

  5. If you have fungus or mildew problems. Use 15 ml of 35% hydrogen peroxide in 1 litre distilled water spray all plants, mildew disappeares. Any fungus’s can be killed buy applying 30ml of 35% hydrogen peroxide in 1 litre distilled water and flood soil. It will also remove any insect and any eggs from the soil. You will need to add enzymes to replace the good bacteria killed in the application. The added oxygen increases fertilizer uptake.

  6. Help! My outdoor starting to flower plants leaf edges are curling and all new growth and flowers are brown. I can’t figure out what is wrong. Can anyone help?

  7. I have it on the trunk of some of my smaller, but best looking budding plants. Wondering if it’s safe to smoke?

  8. […] If fusarium does begin to take hold in the root systems of your plant, there’s very little that you can do to treat it. First of all, it’s very difficult to spot until it’s too late. Second, although indoor growers can help prevent fusarium by using sterile soil, there’s no way to be sure it isn’t present outside in nature. Read more about Fusarium on marijuana plants […]

  9. […] If fusarium does begin to take hold in the root systems of your plant, there’s very little that you can do to treat it. First of all, it’s very difficult to spot until it’s too late. Second, although indoor growers can help prevent fusarium by using sterile soil, there’s no way to be sure it isn’t present outside in nature. Read more about Fusarium on marijuana plants […]

  10. I just read a few articles and learned that papaya extract of lactic acid has amazing results. Also read that wearing flip flops in the garden (which feels natural) is about the worst thing you can do. Toenail fungus is the best carrier known to scientists for being the guilty party in the reciepe for disaster.

    1- Dont over water
    2- add lots of pear-lite to your soil and other peat mosses and fluffy things to ensure prompt drainage and drying.
    3- if you begin to see gnats and little flies coming out of your soil get the actinovate out.

  11. great reading, I justy dealt with this issues over the last 3 months. Licked my ass. I lost 3 plants and saved 7 by using thyme oil and actinovate. Good luck to ya