Hydroponic Root Rot: 5 Symptoms To Watch For (+5 Ways To Prevent & 6 Ways To Treat)

“It’s in the roots, not the branches, that a tree’s greatest strength lies.”

The same could be said for small plants, too.

In fact, your plant’s overall health is tied directly to their root health.

That’s because your plant is largely dependent on its roots to be strong, since it’s the roots that are responsible for both nutrient and water uptake.

And for the roots to thrive, they need oxygen.

When roots don’t get enough oxygen and general aeration, bad things happen. Namely, root rot.

In this quick guide, we’ll explore hydroponic root rot:

• 5 symptoms
• 3 causes
• 5 ways to prevent
• 6 ways to treat affected plants

But first, let’s talk about what root rot is.

What Is Root Rot?

Root rot is a disease that affects the roots of plants. As the name directly states, it causes a plant’s roots to rot.

Root rot results in poor growth and usually leads to the death of affected plants if left untreated.

In hydroponics, root rot happens when roots aren’t aerated properly. It mainly affects plants that are grown in Deep Water Culture (DWC) as the roots in these systems remain constantly submerged in non-circulating water.

A lack of oxygen means poor roots. Poor roots mean poor plants.

5 Symptoms of Hydroponic Root Rot

Look for these 5 signs that your hydroponic plants could be succumbing to root rot:

1. Roots change color from white to dark brown/black
2. Roots become slimy and their texture turns soft
3. Roots begin to emit an earthy odor
4. Stunted and slower plant growth compared to non-affected plants
5. Leaves start to wilt, become discolored, and fall off

3 Causes of Root Rot

The main cause of root rot is suffocation due to lack of air. However, it can also be caused by pathogens.

1. Root rot usually happens when the roots become water-logged and are deprived of oxygen.
2. Pathogens such as Pythium, Rhizoctonia, Fusarium, and Phytophthora also cause root rot, and the chances of this happening are much higher when roots are overwatered. The build-up of bacteria, fungi, and mold also makes it harder for roots to take in oxygen.
3. Root rot can also be caused by using too much or too little fertilizer.

5 Ways to Prevent Root Rot

As always, prevention is better than treatment. Seeing your plants affected by root rot isn’t fun, and treating it can be tough. In some cases, you may have to discard the entire plant, which is time and money wasted.

Do to following to keep root rot at bay:

1. Aerate the water using air stones and pumps to keep your roots well oxygenated. Since the lack of oxygen is the primary cause of root rot, this step serves as a major factor in preventing it.
2. Maintain a sterile environment by sterilizing your equipment. This prevents the growth of bacteria in the roots.
3. Remove debris or fallen leaves. If they fall into the reservoir and begin to rot, your nutrient solution becomes a favorable environment for bacteria to breed.
4. Prevent light from entering the water reservoir. Use reservoirs made of thick materials. Paint the outside (plus any tubing) with opaque colors to keep light out. White helps reflect away light. Use dark colors inside the reservoir.
5. Keep your water temperature down. Lower water temperature means higher levels of dissolved oxygen. Bacteria and other pathogens thrive in warmer water, and the amount of dissolved oxygen also decreases. Aim for a temperature around 65-70°F.

6 Ways to Treat Hydroponic Root Rot

It’s important to identify root rot as early as possible because the disease is contagious and can easily affect other plants if they share a common reservoir.

Take a look at our guide to the best hydroponic systems to learn which methods have common reservoirs and which isolate plants in their own reservoir.

If you know your plant is affected by root rot, take the following measures to help treat the roots:

1. If your plants share a common reservoir, the best way to prevent the disease’s spread it to destroy the affected plant (especially if most of its root ball is compromised).
2. If growing multiple plants together, check for root rot in other plants as well. Isolate the affected plant and replace the nutrient solution.
3. If the disease has just started to affect the plant, wash the roots thoroughly with water, and remove all affected roots using a sterilized pair of scissors. Replant it in a new environment after sterilizing the reservoir and replacing the nutrient solution water.
4. Use chemicals, such as fungicides, chloropicrin, and methyl bromide, to restrict further spread. It’s imperative to identify which fungus has caused the root rot to use an appropriate fungicide. Using the wrong chemicals may actually be more damaging than helpful, as they can accelerate the spread of the disease.
5. Add beneficial bacteria to treat and prevent future root rot. 
6. Find out what caused the root rot in the first place (e.g., a lack of oxygen), eliminate the factor(s), and replant the plants in a safe environment.

Hydroponic Root Rot: Final thoughts

Root rot is a disease that affects plants grown both hydroponically and in soil. It shows symptoms first in roots and then only later in the shoots and leaves.

In hydroponics, it’s easy to identify the disease in its early stages since you have easy access to your plant’s root system, which gives you a leg up when trying to treat it instead of pitching the entire plant (or your whole hydroponic system).

Early diagnosis and treatment of root rot are crucial, but prevention is easier.

Root rot can easily be prevented with a few simple precaustions:

• Ensure roots are exposed to surplus amounts of oxygen
• Prevent growth of unwanted pathogens by preventing light from entering the reservoir, cleaning debris, and maintaining a clean environment.

If you’re battling hydroponic root rot and don’t know what to do, comment below!

Credits

Opening quote courtesy Matshona Dhliwayo.