We talk about root rot a lot around here. It’s a common yet vexing plant disease that can be fatal in some circumstances. To a beginner gardener, it may appear that it occurs when you overwater… but this is only partially accurate.
Because you can’t see the root system, diagnosing root rot can be difficult for untrained gardeners. After all, it’s hidden in the soil, and we don’t recommend digging up your plants on a regular basis to check to see if the roots are still intact.
So, just what is root rot? How can you know whether it’s root rot or anything else? Is it possible to treat root rot? We know you want to know the answers to these questions. So let’s get started on preventing root rot and save your plants from an unthinkably bad end!
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What Is Root Rot?
Let’s start with the basics: what exactly is root rot?
There are several soil-dwelling fungus, molds, and oomycetes, but only a few of these cause root rot. Let’s take a look at the most prevalent culprits, how they form, and what they do.
Pythium
This illness spreads more like an oomycete than a true fungal. It has oospores that can overwinter in soil debris or infected plant material, as well as slender, threadlike hyphae that stretch forth from its host plant.
There are numerous pythium species that have an impact on plants. P. aphanidermatum is more frequent in the nursery sector at temperatures below 68°F, but P. ultimum and P. irregulare are more abundant at temperatures over 77°F. These are the most frequent kinds found in the United States on most houseplants, shrubs, and garden plants, however other species are more prone to harm turfgrass.
In all circumstances, there are two factors that increase the likelihood of your soil becoming infected. This plant thrives in soil that is excessively moist. Furthermore, because it prefers a somewhat salty environment, soils or soilless mixtures with a high salt content are more likely to be polluted. This means that sphagnum peat moss and vermiculite blends, as well as some kinds of coconut coir, are at risk.
Once this contamination has entered your soil, it might be difficult to remove using organic methods. Furthermore, overwatering and overfertilizing your plants might raise infection rates. Overwatering accelerates the cycle and allows pests to gnaw on roots, leaving them vulnerable to infection. Overfertilization with nitrogen suppresses the plant’s natural defense response.
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Phytophthora
A form of water mold causes this sickness. This disease can occur everywhere water gathers or flows. It’s abundant in the Pacific Northwest of the United States, for example, as well as near rivers or streambeds, rice fields, and other flooded areas.
In the garden, phytophthora is most likely to attack shrubs or trees, but it can also affect vegetables such as tomatoes, eggplant, or peppers. It prefers warm, moist environments and will thrive in them, therefore drainage is critical to minimize this vexing cause of rot.
Fusarium
Fusarium oxysporium, a fungus we’ve discussed extensively for various reasons, is also a source of rots. It typically causes root and plant crown rots and can live in the bed for extended periods of time. This is one of the most frequent types in residential gardens and can be difficult to manage.
Other Types of Root Rot
Other fungi can induce decaying damage comparable to the ones mentioned above, but with a more limited target spread.
The largest of them is Rhizoctonia. It is caused by Rhizoctonia solani and attacks a variety of food plants, including soybeans and wheat. It’s quite prevalent, but it’s manageable.
Thielaviopsis basicola is a rotting disease that affects ornamentals and flowering plants. This, like Rhizoctonia, is reasonably manageable.
Leptographium procerum is responsible for procerum rots in trees. It is most common in pine trees.
Finally, Heterobasidion annosum is responsible for annosus rots in pines, firs, and other coniferous trees. It is a serious pathogen in American forestry, but it is less prevalent in residential areas.
Symptoms and Diagnosis of Root Rot
One of the fascinating aspects of these various root rot causes is that they all often induce similar above-ground damage. It’s simple to identify that your plant has rot, but it’s far more difficult to pinpoint which type!
In most circumstances, plants will begin to grow slower or stunted. Yellowing of foliage is possible; with turf grasses, yellowed circular spots on the lawn are possible. As the rotting progresses, the plant may begin to exhibit other dangerous indicators of an inability to absorb nutrients and moisture. Wilting can occur, and trees and larger plants frequently lose their leaves out of season.
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The roots under the soil’s surface will all have different rotting parts. Pythium, for example, begins from the tips of the roots and spreads gradually. As a water mold, Phytophthora will infiltrate through damaged roots. Fungi use their hyphae to gradually press their way into the roots.
People frequently rule out more common gardening concerns first, then go on to more significant disease issues, as they do with many other ailments. However, because all of these types of rot are caused by excessive soil moisture in some way, adopting proper garden care can help prevent them from developing. Ensure that your soil has sufficient drainage, that your garden does not have pooled water or that it is not overwatered, and that your potted plants are not sitting in water trays for extended periods of time.
Root Rot Treatment
The treatment of various rots is very dependent on the type of rot.
There are powerful fungicides that can be used to prevent the spread of certain of these rot forms. These are typically administered directly to the soil and are effective at killing fungus in the garden bed. Most are chemical approaches since organic fungicides that prevent problems in the potting soil are few.
Even these chemical approaches, however, do not operate on all kinds. For example, our top three are all significantly more intricate and can frequently be fatal to your plants. There are few anti-rot procedures that work on them, while a few very strong chemical approaches may have a limited effect.
The addition of beneficial mycorrhizae to your soil during planting appears to benefit in most circumstances. These mycorrhizae have a symbiotic relationship with your plant, sharing space and protecting it from outside damage while sharing the same food and water. Bacillus subtilis, Trichoderma harzianum, and Gliocladium virens are three particularly effective pathogen repellents. Adding them to your soil or straight to the root system before planting can be extremely useful.
Trimming off dead sections of smaller plants can also help to safeguard the rest of the plant. For example, if you discover decaying orchid roots in their pot, carefully remove the plant, trim away the fungus and soft rot, and repot in fresh orchid media with great drainage.
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What Should You Do If the Plant Is Already Dying?
If your plant is already dying, there isn’t much you can do to keep it alive. However, you can still try to grow the plant from healthy cuttings and thereby rescue it.
Choose cuttings that are higher up the plant but still robust. Use sterile soil to root your cuttings and follow standard protocols. Plant it in a different position than the previous plant, as it may be at risk in that location until the fungus is gone.
If you’re unsure which sort of rot has infiltrated the plant’s root system, take the roots to your local garden extension and inquire. It’s preferable to put the roots in a double-zipped zipper-sealed bag so nothing gets on them. The people at the extension office can usually tell you exactly what it is so you can try to avoid it in the future.
Remove your old plant, roots and all, without composting it. You can solarize the soil to kill fungal pathogens, but keep in mind that this can also kill beneficial bacteria in the soil.
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Preventing Root Rot
So, how can you defend your plants in the face of all of these terrifying root destroyers? In this scenario, prevention is considerably superior to seeking a cure. Garden management is essential here.
Choosing Resistant Plants
There are several plant varieties that are resistant to common infections such as fusarium. Look for strains with strong resistance to prevalent fungus strains in your area. You should be able to discover a wide range of plants that can combat most diseases, though they may not be the precise ones you’re used to growing.
Create the proper conditions.
Because all of these spread in some way as a result of damp or soggy circumstances, it’s critical not to overwater your plants. Use soaker hoses or other means to control water frequency and avoid splashing, which can spread plant diseases.
Additionally, work in perlite or big organic materials such as forest products to increase drainage in your potting soil. Commercially available well-draining mixes can serve as the ideal medium for your future gardening initiatives.
Don’t be concerned about removing tainted potting mix from your beds if you’ve already had some root rot. Instead, plant-resistant species or plants that are not sensitive to your specific infection in those areas for a period. Crop rotation is not a perfect science, but it can allow the sun to gradually sterilize your potting media over time.
