Root rot: easy methods to establish, deal with, and forestall it

We talk about root rot pretty often here. It is a common but very annoying plant disease and can be fatal under certain circumstances. To the new gardener, it may seem like it happens when you're above water … but that's only partially true.

It is also a little difficult to diagnose root rot for someone who has no experience just because you cannot see the root system. It's hidden in the ground, after all, and we certainly don't recommend digging up your plants regularly to check that the roots are intact.

What exactly is root rot? How can you tell if it's root rot or something else? Is there any way to treat root rot? We know that you really want to answer these questions. Let's dive in and find out how to prevent root rot and save your plants from an unthinkable fate!

Good products to prevent root rot:

What is root rot?

Root rot comes in many forms and can be fatal to plants. Source: NDSU Ag Comm

Let's start with the basics: what actually is root rot?

A variety of soil fungi, molds, or oomycetes exist, but root rot is caused by a small handful of them. Let's examine the most common culprits, how they develop and what they do.


This disease is not a real fungus, but rather spreads like an oomycete. While it can develop slender, thread-like hyphae that extend outward from its host plant, it also has oospores that can hibernate in debris or infected plant material.

There are a variety of types of python affect the plants. In the nursery industry, P. aphanidermatum occurs at temperatures below 68 ° F, with P. ultimum and P. irregulare being more common at temperatures above 77 ° F. These are the most common varieties found in most houseplants, shrubs, or garden plants in the United States. However, there are other species that are more likely to affect turf grass.

In all cases, there are two things that make your soil more likely to get infected. Over-moistened soil provides the perfect habitat for this species. In addition, soils or soilless mixtures with high salinity are more likely to be contaminated as they prefer a slightly salty environment. This means that peat moss and vermiculite mixtures made from sphagnum are just as vulnerable as some forms of coconut-coconut.

Once this pollutant is in your soil, organic measures can make it difficult to remove. In addition, overwatering and overfertilizing can increase the infection rate in your plants. Overwatering promotes the cycle and can allow pests to nibble on roots and leave them open to infection. Over-fertilization with too much nitrogen suppresses the plant's built-in defense reaction.


This disease is caused by a type of water mold. Wherever water collects or flows, this disease can occur. For example, it is found throughout the Pacific Northwest and along rivers or river beds, in rice fields, or in other flooded environments.

In a garden setting, Phytophthora is most likely to encounter shrubs or trees, but can also encounter vegetables such as tomatoes, eggplants, or peppers. It likes warm, wet conditions and thrives in those conditions. Hence, drainage is key to reducing this pesky cause of putrefaction.


Fusarium oxysporium, a fungus that we covered extensively for other reasons, is also a cause of rot. Typically, it caused root and crown rot and can live in bed for a long time. This is one of the most common forms found in home gardens and can be difficult to manage.

Other root rot

There are other species of fungus that can cause rotting damage similar to the above but have a limited target spread.

Rhizoctonia is the largest of these. Caused by Rhizoctonia solaniIt tends to hit a number of food crops such as soybeans or wheat. It's fairly common but can be controlled.

Thielaviopsis basicola is an often rotting disease of ornamental or flowering plants. As with Rhizoctonia, this can be somewhat controlled.

Leptographium procerum causes procerum rot in trees. It's most common in pine trees.

In the end, Heterobasidion annosum causes annosus rot in pines, firs and other conifer species. It is a major pathogen in American forestry, but not as common in residential areas.

Symptoms and identification of root rot

Annosus root rot symptom on the trunkSome forms of rot, such as this annosus root rot, can be identified by fungi on tree trunks. Source: Pellaea

One of the interesting things about these different root rot causes is that they all typically suffer similar above-ground damage. It's easy to tell that there is some type of rot in your plant, but it's much harder to tell which one!

In most cases, plants begin to grow more slowly or stuntedly. The leaves may turn yellow; In turf grass, you may see yellowed circular spots on the lawn. While the rot continues, the plant may show other serious signs of an inability to absorb nutrients and moisture. Wilting can occur, and trees or larger plants that drop leaves out of season are quite common.

Under the surface of the soil, all roots have different parts that decay. For example, python starts at the root tips and then gradually spreads. Phytophthora occurs as a form of water in damaged areas of the roots. The fungi tend to gradually push their hyphae into the roots.

As with many other diseases, people often rule out more common gardening problems first, and then move on from there to more serious disease problems. Since all of these forms of rot are in some ways due to excessive soil moisture, good management of your garden can prevent this rot from occurring. Make sure your soil is well drained, that your garden is not getting pool water or overwatering, and that your potted plants are not sitting in bowls of water for long periods of time.

Root rot treatment

Root rot symptoms in tomatoesSymptoms of putrefaction include yellowing, stunted growth, wilting, etc. as shown on this tomato. Source: Jnzl

Treating these rot really depends on the variety of rot you are dealing with.

Some of these types of rot have effective fungicides that can be used to prevent further spread. These are usually applied directly to the ground and kill fungi in the garden bed. Most are chemical methods as there are very few organic fungicides that will prevent problems in the potting media itself.

But even these chemical methods don't work for all forms. For example, our top 3 are all much more complex and can often become a death sentence for your plants. Few anti-rot methods work on these, although some very powerful chemical methods may have limited effects.

What seems to help in most cases is applying beneficial mycorrhizae to your soil when planting. These mycorrhizae develop a symbiotic relationship with your plant, safely sharing space with it and protecting it from external damage while sharing the same food and water. Bacillus subtilis, Trichoderma harzianum, or Gliocladium virens are particularly good options, all of which seem to be good at fending off the pathogens. Adding these to your soil or applying them directly to the root system before planting can be very beneficial.

For smaller plants, it is also possible to cut off dead parts to protect the rest of the plant. For example, if you see orchid roots rotting in their pot, you can carefully remove the plant, trim the fungus and soft rot, and repot in fresh orchid media with excellent drainage.

What to do if the plant is already dying

If your plant is already dying, there is not much you can do to prevent it from falling. However, you can still try to reproduce from healthy cuttings and thus save the plant.

Choose cuttings that are high on the plant but still strong. Follow the common methods of rooting your cuttings using sterile soil. Do not plant it in the same place as the previous plant as it can also be at risk at that point until the fungus is gone.

If you are unsure of what type of rot is set in the plant's root system, take the roots to your local garden extension and ask. It is best to wrap the roots in a double zippered pouch so that nothing on them can escape. The branch office staff can generally provide a clear picture of what it is so that you can try to prevent this from happening in the future.

Dispose of your old plant without composting it, roots and everything. You can consider solarizing the soil to kill fungal pathogens. However, keep in mind that this will also kill beneficial microorganisms in the soil.

Prevent root rot

Phytophthora root rot on pepper plantPhytophthora in the root system of a pepper plant. Source: IFDC

How do you protect your plants with all of these creepy root destroyers? In this case, prevention is far better than trying to find a cure. Good management of your garden is key here.

Choose resistant plants

There are a number of plant varieties that are resistant to common pathogens such as Fusarium. Look for strains with high resistance to the strains of fungi that are common in your area. You should be able to find a variety of plants that can fight off most causes, although they may not be exactly what you are used to.

Provide the right conditions

Since all of these will spread in some way due to wet or humid conditions, it is important to avoid overwatering your plants. Try using water tubing or other methods to regulate water frequency and avoid splashes which could spread plant diseases.

Also, work with perlite or large organic materials like forest products to improve the drainage of your potting soil. Well-drained mixes are commercially available and can become the perfect medium for your future gardening work.

If you've already experienced root rot, don't panic as you remove contaminated potting soil from your beds. Instead, opt to plant either resistant species or plants that won't be susceptible to your specific pathogen for a while. Crop rotation might not be a perfect science, but it can cause your potting soil to become naturally sterilized by the sun over time.

The green fingers behind this article:
Lorin Nielsen
Lifelong gardener

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