Chris DeWildt

December 18, 2018 5 min read
December 18, 2018
5 min read

Growers Network’s Disease Profile: Fusarium Wilt

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In this series of articles, Growers Network talks about a few of the most common Cannabis diseases you need to watch out for. Today’s topic: Fusarium Wilt.

Plant diseases can be a nightmare in any grow operation and Cannabis has no shortage of diseases that would love to ruin your crop. So for today’s profile we’re going to discuss Fusarium Wilt, yet another fungal disease you may find yourself dealing with in your grow.

Quick Look

  1. Common Name: Fusarium Wilt
  2. Scientific Name: Fusarium oxysporum
  3. Symptoms: Damping-off of seedlings, wilting, chlorosis and necrosis of leaves and stems, stunted growth, leaf browning
  4. Caused by: Fungus
  5. Timing: All times

Fusarium Wilt

Fusarium oxysporum in a petri dish, courtesy of the US Department of Agriculture.

What is Fusarium Wilt?

Take the worst plant disease you can think of. Now, mix in another bad disease. Then throw in one more. The mental image you’ve probably arrived at is something similar to Fusarium wilt.

Fusarium is a nightmare-level disease for your plants to get. And the worst part? It’s found nearly everywhere in the world. Its spores are most often found in soil, and can be spread by contaminated water or infected seeds.

Fusarium Wilt on cannabis. Image courtesy of Royal Queen Seeds.

Once it infects a plant, it travels through the plant and into the vascular system (xylem and phloem), becoming a systemic infection that is nearly impossible to remove. Eventually the spores and mycelia clog up the xylem, causing the plant to wilt and die from lack of water. When this happens, the fungus invades other plant tissues and nearby plants.

What to look for

When a plant has a severe infection of Fusarium, it will look like it’s not getting enough water. Leaves will die, the plant will wilt, and growth will halt. Even if you’re giving the plant adequate water, it will look like it’s dying of thirst. One of the telltale signs, according to ILGM, is looking for curled leaves that look like they will drop off, but won’t.

Image courtesy of ILGM

How to Treat Fusarium Wilt

The best “treatment” for Fusarium is to prevent it in the first place. However, presuming you’ve caught the disease in the middle of a grow, there are a few steps you can take to limit its effects. First and foremost: Any topical spray or fungicide will not work. As we mentioned above, Fusarium is a systemic infection, meaning that infected plants are basically lost causes, because any remediation will likely render the final product unsafe for humans. Instead, you should focus on making sure the problem doesn’t get any worse than it already is.

Here are some steps you should take:

  1. Quarantine any infected plants immediately. Do not let them stay near healthy plants.
  2. Dispose of the infected plants in a way that does not spread spores. You can stuff them in airtight bags, you can throw them into a furnace, but do not chop them up in open air.
  3. Dispose of any soil the infected plants touched. Like the plants themselves, don’t dispose of the soil near your facility.
  4. Sanitize all equipment that came into contact with the infected plants. This means scissors, shears, gloves, pots, and more. Hydrogen peroxide or rubbing alcohol should help here.

Once that’s done with, you’ll want to take steps to prevent another infection, which leads into our next section...

How to Prevent Fusarium Wilt

This may seem like a “no duh” point, but Fusarium lives in soil. If you don’t grow in soil in the first place, you generally shouldn’t have a problem with Fusarium. It can still be carried in with infected seeds or unsanitized tools, but Fusarium occurrence should be much rarer in a hydroponic setup.

But if you don’t want to switch your whole grow to hydroponics, there’s still plenty of options available to you. Here’s a few:

1. Maintain healthy soil.

It might seem strange to suggest, but Fusarium prefers muddy, cold, and poorly-oxygenated soils. A healthy loamy soil will go a long way towards fighting Fusarium. Additionally, you can amend the soil with natural antifungals such as nettle and horsetail, and you can also inoculate your soils with a healthy variety of microbes that will compete with any Fusarium spores that show up.

You can also keep soil in separate pots to prevent the spread of any Fusarium in the future as well.

2. Sanitize, sanitize, sanitize!

You should build in sanitization protocols into your grow. Tools and clothes in the grow should be cleaned on a regular basis to prevent cross-contamination. This will go a long way towards preventing other disease and pests as well!

3. Only source genetics you trust.

Fusarium can travel in infected seeds, so if you’re growing from seed, make sure to take steps to limit potential infections in your propagation rooms. If you’re growing clones, the symptoms should become obvious very quickly. If you start from a trusted supplier, you are less likely to have issues.

4. Don’t create conditions that favor fungus.

Fusarium is a fungal species, and as such, benefits when conditions are cold and wet. Make sure to avoid the dewpoint, keep humidity levels within reasonable ranges, and don’t overwater your plants. Preventing the formation of fungus is easier than cleaning up afterwards.

Related Article: Using Climate Control to Prevent Disease

So now you know a bit about Fusarium Wilt and what you can do to prevent it from ruining your grow. Have additional questions about Fusarium Wilt? You should join our forum where you can post pics and ask our expert community about this topic or any other!

Happy Growing!

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About the Author

Hunter Wilson is a community builder with Growers Network. He graduated from the University of Arizona in 2011 with a Masters in Teaching and in 2007 with a Bachelors in Biology.