How To Treat Root Rot In Hydroponics - No Plant No Life

Saturday, December 3, 2022

How To Treat Root Rot In Hydroponics


Have you experienced hydroponic root rot before? I know how you feel, seeing your beloved plants start to wilt with the roots turning brown can be very frustrating and debilitating at times. 

Root rot occurs based on a variety of factors but in this article, I'm going to show you the easiest way to treat root rot in your hydroponic garden, so you don’t get to bother about losing your plants ever again.

If you're new to hydroponics, check out what you need to know before starting a hydroponic system.

What Is Hydroponic Root Rot and Causes of Hydroponic Root Rot?

The cause of root rot in hydroponics is similar to that of conventional or traditional farming.

When root rot occurs, the affected plant may appear wilted, experience poor growth, lack vigor and in some severe cases can even lead to death.

One  major reason why your hydroponic plants may experience root rot is over deposition of nutrients in the hydroponic  solution.

Sometimes we get carried away by the fact that our plants need to feed on these essential nutrients but it becomes a problem also when you add too much of it to the water.

When too much nutrient is added to the water, your plants may experience nutrient burn, a condition that occurs  when your plant root absorbs excess amounts of nutrients from the hydroponic solution.  

The over deposition of nutrients increases the concentration of the water resulting in the plant roots turning brown which eventually leads to root rot.

In hydroponics, root rot can also  occur when you don’t regularly change your water or sterilize your equipment. This may give room for  fungi to thrive which ends up affecting your plants.

Root rot may also occur when you fail to provide oxygen to your plants using an air pump or by failing to support the roots with clay pebbles.

The air pump helps to generate dissolved oxygen which is very important for the optimal growth of your plant and also helps to keep pathogens at bay as most organisms responsible for root rot thrive majorly in an anaerobic environment.

The absence of dissolved oxygen will create room for the dormant fungi spore to become active and attack the weakened plant roots resulting in wilting because the plant is unable to uptake the necessary nutrients.

The major organism that causes hydroponic root rot is  Pythium species, an Oomycete that thrives in anaerobic environment, it feeds on the roots of the plant resulting in wilting and death.

The two Pythium spp commonly responsible for hydroponic root rot are;

  • Pythium aphanidermatum- Thrives in warmer temperatures (75-95 °F
  • Pythium dissotocum - Thrives in cooler temperatures (60-85  °F)

Other organisms that cause root rot in hydroponics include Phytophthora spp, Fusarium spp and Rhizoctonia spp.

These organisms attack the root of the plant making it look discolored and unhealthy  and also produce a pungent odor  like that of a rotten vegetable.

How Do You Identify Root Rot in Hydroponics?

One of the major challenges that most hydroponic growers face is the identification of root rot.

Most at times root rot may be hard to identify as it can be easily mistaken for something else. 

That’s why I strongly advise you to properly diagnose your plant before drawing conclusions or get an expert from a plant diagnostic clinic to help you with the diagnosis. 

When a plant is affected by root rot the root will not be able to take up nutrients to the leaves thereby causing the plant to show some  symptoms.

General symptoms of root rot includes: 

  • Floppy unhealthy leaves
  • Yellow/brown  leaves
  • Unequal growth pattern 
  • Brown unhealthy roots
  • Pungent odor from the roots

Symptoms of Pythium Root Rot 

Generally, the most common cause of hydroponic root rot  is due to the presence of Pythium spp.

Root rot reduces nutrient and water uptake resulting in low plant yield.


Some common symptoms of Pythium spp includes:

1. Damping -off

One of the most common  symptoms of Pythium root rot commonly seen in young seedlings is damping-off. This is the eventual collapse of young seedlings.

A classic damping-off of seedlings 

The first photo is a kale microgreen as you can see the classic damping off. The  middle photo is a lettuce seedling and the last photo is an arugula seedling showing a classic damping off. 

2. Wilt and Leaf Yellowing

A lettuce plant infected by Pythium spp

The first photo is a picture of a lettuce in deep water culture (DWC) and it’s actually wilted, the second photo is also a lettuce in a hydroponic DWC system with a combination of wilting and Pythium spp present in the roots. 

The yellowing of leaves also resembles nitrogen deficiency meaning it might also be as a result of a combination of factors.

3. Reduced Growth

Pythium spp can affect the overall growth of the plant as you can see from the photo below.
Reduced growth due to Pythium infection

The  photo on the left shows a five week old spinach inoculated with Pythium spp and on the right is  a five week old healthy spinach plant free of Pythium spp.

There are both of the same age and this goes to show how susceptible spinach is to Pythium.

The small plant on the left is a three weeks old  lettuce seedling infected with Pythium  and the one on the right is a three weeks old lettuce seedling free of Pythium.

From this, you can see how the growth of your plant can be seriously reduced if they are infected with Pythium.

4. Reduction of Root Mass

Another symptom of Pythium root rot is reduction in root mass. When your plant is infected by Pythium, one of the ways to easily detect it is in the length of the root mass. 

Reduction in root mass due to Pythium infection

The plant roots become shortened as can be seen from the photo above. A plant with a healthy root will have longer root mass than a plant infected with Pythium.

5. Root Discoloration

Another symptom to watch out for is root discoloration. The root of a plant infected by Pythium will show either a yellowish or brownish discoloration.

Discoloration in roots due to Pythium 

The last photo above shows the early stage of Pythium infection as  some healthy white roots mixed with yellowish-brownish roots can be seen in the photo.

The second and first photo shows Pythium infected roots with yellowish-brownish discolorations.

6. Rat Tail

Here is a photo of how Pythium can actually make  plant roots brittle and easily break apart.

This is most commonly called ‘’Rat Tail’’, it’s a classic symptom of Pythium root rot. 

Cortex of roots sloughing off due to Pythium infection

The above photo shows the cortex of the roots sloughing off and the vascular system being exposed to the outside environment. 

When you see this on your plant roots, just bear in mind that your plant might have been infected by Pythium. So this is just another symptom to look out for.

7. Non-uniform Growth Patterns

You also want to look out for the growth patterns of your plants just to get an idea of what is going on.

Non-uniform growth patterns don't only apply to Pythium, this can also be seen in other disorders as well.

However, usually when disease is present you will see more of a non-uniform pattern because it’s actually a living organism and not all of them were subjected to the same environmental conditions or field. 

The photo above shows yield loss due to Pythium outbreak at a hydroponic leafy green commercial facility.

As can be seen from the photo, the growth pattern is kind of spotty patchy, not a very uniform growth pattern.

After noticing a non-uniform growth pattern like this, the first thing you want to do is to send a sample to a diagnostic clinic and get them to diagnose it for you before taking any further action.

8. Check Plant Roots Quality

Another thing you want to look out for is the quality of your plant roots. Although checking the leaves and other parts of the plant is good, you also want to see what's going on with your plant roots.

The first photo above shows really healthy white roots free of Pythium whereas the second photo shows necrotic brown roots infected with Pythium root rot at a commercial facility.

How to Prevent Hydroponic Root Rot

As the saying goes ‘’prevention is better than cure’’, it is far better to prevent hydroponic root rot occurrence than to treat an already infected plant.

There are several measures you can take to prevent inoculum from entering your hydroponic system. Some of these measures includes:


1. Sanitize In-between Production Cycle

Sanitizing in-between production cycle is really very important if you want to prevent root rot occurrence in your hydroponic system.

Surface sanitization is paramount to keeping your system clean and disease free. 

To surface sanitize;

  • Get rid of dust, debris and infected plants from the system and media.

  • Ensure to wash all production trays, rafts and keep the floor clean.

  • Sanitize surfaces with oxidizing agents such as SaniDate.

2. Inspect Seedlings and Treat With Preventive Drenches

Inspecting seedlings is really important before starting your growing process because you want to start your seedlings in a clean environment and hopefully end in a clean environment.

To inspect your seedlings;

  • Check the seedlings for any possible symptoms of root rot before transplanting into the system.
You can manually check your trays to ensure that all your plant roots are white and healthy, and that there is no brownish or yellowish discoloration present in the roots.

You can use hydrogen peroxide products such as Oxidate and Zerotol as root drenches to keep your seedlings from root rot infection.

Ensure to read the labels as each product usually comes with the recommended doses for drenching seedlings before putting them in the system.

How To Treat Root Rot With Hydrogen Peroxide 

Although taking preventive measures at the beginning of your growing process is considered the best way to prevent root rot from ever occurring in your hydroponic system. 

Sometimes due to some factors, you may still see some of your plants coming up with root rot issues.

If you have a case of an already infected plant, don’t panic, there is still an effective method you can apply to get rid of root rot from your hydroponic system.

Hydrogen peroxide with the chemical formula H²O² is a chemical compound that shares great similarities with water although has a higher viscosity than water.

Hydrogen peroxide can be used in a lot of ways, at home, in your garden, and in industry. 

When used at home, it is usually diluted with water to reduce the concentration but the industrial application makes use of a higher concentration of the compound.

Hydrogen peroxide occurs naturally and is safe to use in the garden because it decomposes to form water and oxygen creating a more thriving environment for your plant roots.

How to Apply Hydrogen Peroxide to Plant

To treat your infected plant roots, start by preparing a solution with 3% hydrogen peroxide. 

1. Add 2-3 teaspoons of 3% peroxide per liter of water or 2 tablespoons per gallon of water in a bowl or container.

2. Empty the water in your hydroponic container. 

3. Rinse the roots with tap water.

4. Pour in the hydrogen peroxide solution into the hydroponic container.

5. Submerge the roots inside the hydrogen peroxide solution.

6. Allow for 24 hours.

7. After about 24 hours, pour out the hydrogen peroxide solution from your hydroponic container.

8. Replace with pure water and allow for 24 hours before adding your nutrient solution.

9. After  some days, you should start seeing some results.

Can Plants Recover From Root Rot in Hydroponics?

After treating your infected plants, you should start seeing some result about 7 days after treatment. 

Infected plants can be revived if the treatment procedures are correctly administered. You can also try to remove the leaves that were damaged due to root rot to boost the plant growth.

As the plant gradually recovers, ensure to feed it with the appropriate nutrient to enhance its optimal growth and overall development.



Root rot can be very devastating to your plants if not correctly treated.

Pythium along with other fungi are the major causes of hydroponic root rot.

When a plant is infected with root rot, there are some major symptoms to watch out for as outlined in this article.

Symptoms of Pythium root rot vary from damping-off of young seedlings to wilting, root discoloration and many others.

Although these organisms can be very devastating to your plants, there are also numerous methods to prevent or treat an already infected plant.

Hydrogen peroxide proves to be very effective in treating and preventing root rot in hydroponic system. 

Whether it's your first time experiencing root rot or you are looking for more ways to prevent root rot occurrence in your grow system.

I hope with this article you can now prevent and treat your plants affected by root rot without bothering about the effectiveness of the treatment method. 

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