Tomato growing is an all-time favorite pastime of the avid gardener.
Picking ripe fruit ready to eat straight from the vine is so rewarding.
Especially when you consider all the things that can go wrong.
There are dozens of things that can ruin your tomato crop yield. None more devastatingly than tomatoes with root rot.
The bite into a fresh home-grown tomato is the taste of victory. When that’s being threatened, you need to take action…fast action to be more precise!
Read on to discover the causes, fixes, and preventative steps you can take to make certain that you enjoy that delicious taste of victory!
Table of Contents
Tomato root rot
The main sign of root rot on tomatoes is downward leaf curl. Other symptoms including yellowing leaves, brown stems, leaf drop, wilting, and premature leaf drop. Inadequate irrigation is often the cause; others are soil-borne fungi infections including phytophthora, brown (corky) root rot, and fusarium.
Symptoms of tomato root rot
The signs of tomato root rot are numerous, but the order you see the symptoms can indicate what the underlying cause is.
For example, if you notice your leaves start to rot but the roots look healthy, that’s probably tomato blight that can be fixed by pruning off diseased leaves.
When the roots are being damaged, one of the most common signs is downward leaf curl. Don’t confuse this with upward leaf curl because they represent different problems.
Downward leaf curl is a sign of root rot. Upward leaf curl is the plant conserving moisture until it needs it.
Whenever you see tomato leaves curling, it’s a sign of an irrigation issue. Upward leaf curl isn’t a worry. Just don’t add water. Downward leaf curl indicates the roots can’t deliver water throughout the plant.
When you notice downward leaf curl accompanied with drooping, that’s a definitive sign of tomato root rot that without being addressed, leads to tomato plants dying of rot.
When the roots are cankered, discolored, stems turning brown, the plant wilts, droops and starts to drop its leaves… that’s early signs of diseased roots, or the roots rotting because of too high a moisture content in the soil.
Soil diseases that rot the roots of tomato plants
Brown root rot (corky root rot)
Brown root rot, which is also referred to as corky root rot is caused by the pyrenochaeta lycopersici pathogen.
It lays dormant in soil as microsclerotia, then germinates when temperatures are between 60-degrees Fahrenheit, and 68-degrees Fahrenheit.
It’s one of the reasons to aim for maintaining growing temperatures above 70-degrees Fahrenheit.
Unlike fusarium and similar to soil fungi, corky root rot doesn’t infect the xylem tissue of tomato plants.
The rot is contained to the roots, but it does deprive the plant of vital nutrients, causing tomato leaves to wilt, loss of plant vigor, and ultimately less fruit yield.
The signs of corky root rot are tomato leaves wilting, drooping, and premature leaf drop.
If you see those present, look at the roots. Pyrenochaeta destroys the feeder roots, causes brown lesions on the shallow roots, and on the mature roots, they swell up, turn brown, and eventually, the stems crack.
To treat this particular strain of fungi in the soil, sanitization, either with hot steam or solarization is best used to increase heat to the extreme that kills the fungi.
Phytophthora root rot
Phytophthora root rot is far more distinctive than that of corky root rot. This will cause brown lesions on all the roots, not just the shallow roots.
Right above the lesions is where you’ll see the xylem of the stems yellow, brown, girdle and rot away to nothing.
Like moist soil-borne fungus infections, it takes certain climates for the spores to germinate. In the case of phytophthora, that climate is overly moist soil. Contributing factors include overwatering and poor draining soil.
Good practice to prevent phytophthora root rot is to rotate crops and only water when the soil is dry. You only need to water tomato plants with a couple of inches of water per week, and that’s only if the soil dries out within that week. If the soil’s still moist, hold off on watering.
Important to note is that phytophthora is soil-borne but it doesn’t always result in tomato plants dying. There are some disease-resistant varieties, but even those will suffer from a loss of fruit yield.
There are also different pathogens of phytophthora. Phytophthora capsici can cause tomato plant stems to turn purple to brown shade.
The phytophthora parasitica pathogen can result in buckeye rot on the fruits that are in direct contact with the soil.
To prevent fruits rotting, it’s a good idea to know how to properly stake tomato plants because they rarely do well when left scattered on ground soil.
Staking your tomato plants protects the fruits against rot but it doesn’t protect against root rot.
How to prevent tomato root rot
Maintain consistent temperatures
Ideally, the temperatures should be maintained between 70-degrees Fahrenheit and 85-degrees Fahrenheit. Numerous fungi pathogens in the soil thrive in lower temperatures below 70-degrees Fahrenheit.
Improve drainage
If you struggle with drainage, mound your soil to make a landscape berm, which elevates your tomato plants above ground soil, helping water drain more efficiently.
Maintain the right soil pH balance
Check your soil pH is the right acidity for the type of tomato plant you’re growing. And use the right type of fertilizer for tomato plants to deliver the nutrients your tomatoes need for growth, or fruiting depending on the stage your plant is at.
Keep in mind that high doses of nitrogen can alter your soil acidity. Excessive use of fertilizer can cause root damage, making it more susceptible to an infectious disease.
Think before you water
Be really careful with watering, especially if your area is prone to heavy rainfall. If that’s the case, consider growing against a south-facing wall, or under a canopy.
Use mulch
Mulch around the base of your plants with wood chips or similar mulching material to soak up excess moisture.
When using this technique, remember that the moisture is only retained and will release back to the plant, so you won’t need to water as often during dry spells.
Enrich your soil with compost
Apply compost to enrich your soil, and use the right soil to compost ratio based on whether you’re growing in ground soil, raised garden beds or growing tomatoes in containers.
The amount of compost you use makes a difference.
Get the spacing right
Lastly, but far from least important is to know how far apart to plant tomatoes because spacing effects nutrient delivery, soil drainage, and air circulation. All contributing factors to possible root rot development.
The most effective way to prevent root rot on tomatoes is to plant with enough space between them for a deep rooting system to develop.
Preferably, enough space for a deep taproot with multiple lateral roots, rather than a shallow fibrous root system, which is mainly just thin roots that won’t stand a fighting chance against soil fungi, not to mention insect bites from the likes of caterpillars, tomato worms, and nematodes.
How to treat tomato root rot
The best treatment protocol for tomato root rot is the same as any plant experiencing root rot. Trim away the damaged roots (brown and black) keeping only the healthy white roots.
If you catch the signs early enough, there might still be enough healthy roots for the plant to make a comeback on its own.
If there’s a fair chunk of the root system lost to root rot though, you’ll need to follow the guidance on how to revive a dying tomato plant because that is what will happen.
In instances when a soil-borne fungus infection is suspected, the plant should be removed, trashed and the soil treated or quarantined. Fungi in soils will continue to infect similar plants in the Solanaceae family.
To treat a fungal infection in soil, heat treatment, either steam or solar, is beneficial as the higher temperatures can kill fungi better than any fungicide can.
Frequently Asked Questions related to tomato root rot
Is blossom-end rot caused by the roots on tomato plants decaying?
These are two different conditions. Root decay happens because of irregular irrigation in the soil, or a fungi infection. Too high or low moisture can contribute to blossom end rot, but more often than not, it’s a nutrient imbalance. Usually, lacking calcium or excess nitrogen.
Why do my tomato plants have brown stems but healthy leaves?
A number of pests lay eggs in stems that hatch, grubs emerge, do some feeding, then fly off. The stem damage restricts water distribution resulting in upward leaf curl. Unless the browning extends down to the roots, it’s unlikely to need pruned. You only need to remove stems attached to rotted roots.
Daniel has been a plant enthusiast for over 20 years. He owns hundreds of houseplants and prepares for the chili growing seasons yearly with great anticipation. His favorite plants are plant species in the Araceae family, such as Monstera, Philodendron, and Anthurium. He also loves gardening and is growing hot peppers, tomatoes, and many more vegetables.