Fusarium Fungi and Cannabis Plants

Here at Growbarato.net we like to keep our customers and growers informed and up to date with all of the latest information regarding plant, seed and clone care. Today we’re going to talk about fusarium fungi and cannabis plants – this deadly fungi can devastate your entire crop within a matter of hours, whether it’s cannabis, tomatoes, onions or pretty much any other kind of crop.
Petri dish

Fusarium Fungi

Fusarium is a type of fungi, or rather an entire family of fungi, characterized for being stringy. This type of fungi can be found in almost every type of soil on the planet, especially in warmer areas. These fungi can stay dormant for years and years until it found the right chance to infect roots, which happens in a flash.

Fusarium fungi in cannabis plantsThe different types of fungi can be classified depending on the effect that they cause on the infected plant, which can show in the trunk, in the roots and even in your plants “veins”. The names given to these types of fusarium are usually related to the type of plants that they’re usually found in, although it doesn’t really matter when it comes down to it; if your plants catch any variant of this fungi, all you can do is get rid of the infected plants and disinfect the area entirely.

Types of Fusarium fungi that affect the stems/trunk:

  • Fusarium Sulphureum
  • Fusarium Graminearum
  • Fusarium Lateritium
  • Fusarium Sambucinum
  • Fusarium Avenaceum
  • Fusarium Culmorum

Types of Fusarium fungi that affect the roots:

  • Fusarium Solani

Types of Fusarium fungi that affect plant veins:

  • Fusarium Oxysporum

These are just a few of the different types of Fusarium Fungi out there, and possibly the most common ones, although there are hundreds of species and sub-species in the wild. When growing cannabis the two most common types of Fusarium Solani and Fusarium Oxysporum.

How does Fusarium spread?

Fusarium and its sub-species are generally found in decomposing elements in soil or at ground-level – this includes decaying leaves, branches, trunks etc. Depending on the species, it can spread via direct contact or via spores in the air.

  • When it comes to fusarium fungi that affect your plants’ roots and cause ever-feared root rot, keep in mind that the infection generally happens through the roots themselves. It can also spread through open wounds on your plants or parts that are drying off, whether it’s the roots or the leaves/stems.
  • In regards to the type of fungi that affects your plants’ vascular system (plant veins), remember that this type can also stay dormant like the root variant. These spores can affect your plants even if they don’t have any open wounds, especially near their roots, although any unhealthy parts of your plants will make it much easier for this fungi to attack. Once it gets at your plants it’ll begin to spread rapidly. Once it gets inside the plant and begins affecting the xylem (elements that help transport water and nutrients) your plants are officially done for.
  • Last, but not least, you also might encounter a specific type of Fusarium that attacks cannabis plants and causes what growers sometimes call stem/trunk cancer. It spreads in the exact same way as the root fusarium strains, although it’s more probable that your plants become infected via some sort of open wound. It usually gets in through broken branches after pruning and forgetting to cover up the wound or if you’ve accidentally opened a wound when training and adjusting the branches.

fusarium fungi in cannabis plants                    Fusarium fungi in cannabis plants

Fusarium Symptoms

Fusarium fungi have various different ways of showing, which is why it’s a good idea to routinely check your plants for particular symptoms, which can be checked on the leaves, branches, trunk and roots. If you find any of these symptoms on your plants, you should begin to worry.

  • Fusarium fungiYellowing lower leaves.
  • Premature withering of yellowed leaves.
  • Trunk discoloring – pink, red, brown, yellow and violet.
  • Decolored leaves curling upwards.
  • Roots turning brown (necrosis).
  • Individual drooping branches compared to the rest of the plant.
  • Entire plant drooping.
  • Soil surface is sticky or gooey.
  • Soil is constantly humid and smells bad.
  • Otherwise healthy plants that aren’t absorbing any water.
  • Calluses or inflamed trunk.

How to prevent Fusarium Fungi

In order to avoid having Fusarium issues you’ll need to take preventive measures; if your plants become infected, there is simply no saving them. So, you’ll need to undertake a few prevention measures such as cleaning and disinfecting your growing area – they may seem extreme, but if you suspect that your plants are at risk, you’re much better off taking extreme caution.

  • Disinfecting & cleaning | Indoors

One of the best things you can do for your plants happens before you even plant them; completely disinfecting your grow room, including the floor, walls, ceiling and windows. You’ll also need to disinfect all of the materials and devices that you plan on using, especially if they’ve been used to grow cannabis before. This includes flowerpots, trays, lighting systems, ventilation systems etc. You should also have a specific set of clean clothes set aside for wearing in your grow room. This stops you from accidentally bringing spores or insects in on your clothes.

Preventive products

  • Disinfecting & Cleaning | Outdoors

It’s a bit harder to fully disinfect an outdoor growing area. That’s why you should carefully select the area that you’ll be growing in – check out the plants in the area for signs of Fusarium fungi. If you even suspect that you might have seen something, do not plant there. Once you’ve found a relatively clean spot, get rid of all of the weeds in the area and any dying leaves or other dying vegetation. After making the necessary holes for the plants if planting in the ground, you’ll need to fill them in with quality substrate that has been enriched with beneficial bacteria or mycorrhizae.

You can also use the soil solarization method to reduce the chances of fungi and pathogens. This technique consists of covering your growing surface with a sheet of see-through plastic. This allows the soils temperature to increase to temperatures that certain fungi can’t grow in.

Fusarium fungi

  • Substrate for warding off Fusarium

The substrate that you decide to use is quite important, as certain brands contain special fungi and bacteria that help your plants and protect their roots from issues such as Fusarium. This also allows you to know exactly what’s in the soil you’re using – if you use soil from your garden it could already have some sort of pathogen or fungi in it. You’ll also need to make sure that the soil isn’t wet for long periods at a time and stop it from heating up while wet, which can increase the chances of Fusarium appearing. Use perlite and clay, as well as coco coir, in order to give your plants’ substrate more oxygen, which helps it to get rid of humidity faster than normal peat soil.

  • Temperature and humidity

Fusarium tends to stick around in areas where the temperature and relative humidity tend to be quite high. In order to reduce this risk try and keep your plants’ substrate no higher than 25°C, as well as the temperature when growing indoors. In as far as humidity, you’ll need to try and avoid letting your plants’ substrate stay wet for too long, make sure they have plenty of ventilation and aren’t shaded. You’ll also need to control the relative humidity when growing indoors; it’s much harder to control these parameters outdoors, you simply need to pick the spot carefully.

Seed germination

  • Germinating seeds

When germinating cannabis seeds you’ll need to be careful when it comes to humidity – you need high levels of humidity to germinate cannabis seeds (70-90%). The best way to reduce risk is to use paper towels to germinate, as it’s generally the cleanest material to germinate in. When hydrating them you can use distilled water to reduce the risk even more, or bottled water. You can also go a step further and use trichoderma fungi to give the seeds a protective layer or place them in a glass of water with a couple of drops of peroxide.

  • Rooting clones

You’ll need to take the same preventive measures with clones as with seeds. If you’re taking the cuttings yourself, make sure the plant that they are taken from is in perfect health, avoid condensation inside your propagator/greenhouse, and make sure to disinfect everything before using it.

In the case that you happen to get your clones from someone else, you will need to quarantine them before putting them with your other plants. If you can, try and visit the area that they were grown in to check out how clean it is before buying them. You’ll also need to ask the grower what substrate they used to root the clones and what products they used, which should be organic and trichoderma fungi.

  • Nutrition

Another important factor is your plants’ diet. When growing cannabis it’s pretty easy to accidentally over-feed your plants. Nutrient excess tends to damage their roots, which is an open door for fungi, including Fusarium. You’ll need to make sure that your plants’ substrate doesn’t have too much nitrogen and potassium – both deficiencies and overfeeding can make it easier for Fusarium to infect your plants. You’ll also want to keep a close eye on pH levels; if your plants’ soil or water is too acidic, you’ll be increasing the chances of Fusarium.


  • Clean and disinfect all growing material.
  • Clean and disinfect the area that you’ll be growing in.
  • Use spongey, airy substrate.
  • Use fungi and beneficial bacteria.
  • Try and use clean clothes, gloves, and avoid contact with other plants.
  • Use white flowerpots.
  • Avoid soaking the substrate.
  • Do not let your substrate go over 25°C.
  • Keep careful control of relative humidity in each phase.
  • Do not reuse soil.
  • Use soil solarization outdoors.
  • Don’t overfeed.
  • Avoid excess nitrogen and potassium.
  • Keep pH levels between 6 and 7.
  • Only germinate quality seeds using quality, clean water.
  • Quarantine any clones that you didn’t take yourself.
  • Use preventive products routinely.
  • Use trichoderma harzianum fungi.

Prevention truly is the only method to avoid Fusarium killing off your plants; these methods may seem like a lot of work, and they are, although if done properly your plants will grow healthily without the risk of fungi infections, not just Fusarium – these methods can be used to keep many different types of pathogens and insects away from your plants.

Fusarium FungiFusarium fungi

Fusarium Fungi: Conclusion

Fusarium is one of the most dangerous fungal infestations that any type of plant can get – once your plants have been infected there’s no going back, they simply can’t be saved. That’s why it’s incredibly important to take as many preventive measures as possible before it’s too late; keep everything as clean as possible.

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