Tomatoes Black Spots On Leaves – Septoria leaf spot can cause severe losses in tomato plants. Learn how to recognize the symptoms of this fungal disease and what culture controls you can use to prevent or reduce infection with this guide.
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Tomatoes Black Spots On Leaves
If you don’t already have enough diseases to worry about when growing tomatoes, add Septoria leaf spot to the list.
How To Diagnose Spotty Tomato Leaves
It can be one of the most destructive diseases of tomato plants and is a particular problem in areas prone to long periods of wet, humid climates.
Septoria leaf spot and early blight both appear as spots on the leaves, but they’re easy to tell apart if you know what to look for. We’ll help you with that so you can decide how to proceed.
Neither your greenhouse seedlings nor your adult plants are safe from Septoria, and this fungus can attack at any stage of development.
Why Are My Tomatoes Dying?
Small spots on the lower leaves of your tomato plants are the first sign that your tomato plants are infected with this fungus.
When infected, the undersides of the leaves have many small, water-soaked spots about 1/16 to 1/8 inch in diameter.
These spots have dark brown edges and gray or brown centers. Lesions may coalesce into larger patches as they mature.
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Mature lesions have dark brown structures at their centers that look like black pepper spots.
The fruiting bodies of mushrooms that produce spores are visible to the naked eye.
This fungus rarely infects fruit that is edible, although it can cause stains on stems, flowers, and inflorescences.
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Severely affected leaves turn yellow before they dry up and fall off. Spraying water can transmit the disease upwards to young leaves.
Because of the many leaves, the fruit can sometimes be scorched by the sun.
Aside from the fact that early blight usually occurs early in the season, there are two main ways to tell if an infection is caused by the fungus or not.
Early Blight Of Tomatoes
Pygnidia are not visible in early rot lesions. So if you see black spots, your tomato plants may be infected with septoria.
Splashing water is a common way of spreading these spores, but tools, insects like bugs, and even your hands and clothing can spread them.
Spores germinate within 48 hours, leaf spots can form within five days, and pycnidia within seven to 10 days. The fungus can produce more spores within 10 to 13 days.
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However, spores only infect plants when moisture is present, so infection is more likely on rainy days or in areas of prolonged frost.
Many plants of the nightshade family are susceptible to infection by this pathogen and serve as potential hosts. There they can produce more spores that can infect tomato plants.
These include garden crops like potatoes and eggplants, and common weeds like nightshade, jimsonweed, horse nettle and sweet ground cherry.
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Nightshades often survive the winter and can harbor fungi that can infect your tomato plants while conditions are still favorable.
There are several steps you can take to control this disease, most of which involve removing the original spore sources.
If you catch an infestation early, you can prevent it by removing infested lower leaves and burning or destroying them.
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Mulching your plants reduces the likelihood of spores spreading through splashy soil that contains a mixture of spores and plant debris.
Using overhead watering can significantly increase the risk of infection. To avoid this rule, water early in the day and use a drip hose at the base of the plants.
Encouraging good aeration allows plants to dry quickly after wetting, reducing the likelihood of existing spores germinating.
Bacterial Spot Of Tomato And Pepper
Cutting off the bottom leaves also helps thin out the plants and helps the remaining leaves dry quickly after they get wet.
If you have a garden, consider removing the plants and discarding them at the end of the season. If you grow your plants in containers, disinfect all containers before reusing them.
If you’re growing your tomatoes in a field, plow the plants deeply so the tissue doesn’t act as a source of spores. Plant tissue must be fully decomposed or it will carry fungal spores into the next season.
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It’s always a good idea to rotate your tomato plants where you grow them, as many pathogens can survive in the soil.
If you are controlling Septoria leaf blight, wait two to three years before growing nightshade plants in that spot again.
This fungus can survive in your supplies and cages even in cold weather, so disinfect them if you reuse them.
Early Blight Treatment, How To Treat Infected Tomato Plants With Black Spots
You can do this by spraying them with 70 percent rubbing alcohol. Another option is to soak them in 10 percent bleach, but be sure to rinse them thoroughly as bleach can damage your plants.
If your plants are severely infested, you have the option of using fungicides. They will not cure infected leaves, but can prevent the infection from spreading further.
A recommended and commonly available product is Bonide Fung-onil Concentrate, which can be found at Tractor Supply.
How Can I Keep My Tomatoes From Getting Leaf Spots?
It is a combination of copper and sulfur that has been used to combat fungus since the 19th century.
Apply these chemicals at seven to 10 day intervals throughout the season, beginning at the first sign of infection.
Check the leaves regularly to make sure there are no visible spots. This will let you know the fungicide is working.
Stem Turning Black On Tomatoes
While it’s possible to nip this infection in the bud, Septoria leaf spot can be a serious problem when you’re growing tomato plants.
The fungus doesn’t usually affect the fruit, but an infected tomato can lead to poor growth and even destroy your crop.
Using multiple culture controls can help prevent infection. However, if this disease affects your plants despite your best efforts, you may need to use fungicides to keep it under control.
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Have you encountered this disease? Did you manage to save your plants? Let us know in the comment section below.
For more information on pests and diseases that can affect your tomato plants, check out the following guides:
© Ask the Experts, LLC. All rights reserved. You can find more details in our terms and conditions. Product photos by Arbeco Organics and Tractor Supply. Uncredited photos: Shutterstock. With additional writing and editing by Alison Sidhu.
Black Spots On Tomato Leaves
Helga enjoyed George’s childhood and read about rare plants and greenhouse plants that did not grow in Delaware. Now that she lives near Santa Barbara, California, she enjoys growing lots of these outdoors! Intrigued by her childhood discovery that plants produce chemicals to protect themselves, Helga embarked on further academic studies, earning two degrees specializing in plant diseases. He has a BS in Agriculture from Cornell University and an MS from the University of Massachusetts Amherst. Helga then returned to Cornell to do a PhD studying one of the plant defense model systems. In 2009 he switched to writing full-time. Tomatoes are one of the favorite plants of home gardeners, no wonder. In ideal conditions, homegrown tomatoes are large, red, juicy and tasty. However, if you’ve ever tried growing tomatoes at home, you’ve probably encountered wilted plants or black spots on tomato leaves.
Although tomatoes are relatively easy to grow, they do have their share of pests and diseases. Diseases such as anthracnose and blossom end rot affect fruit. Pests like aphids and whiteflies are also known to cause problems with tomatoes.
“What Causes Black Spots on Tomato Leaves?” Have you heard that before? The cause is often a fungus, which can be a bacterium or a virus. These diseases are spread through seeds, soil, insects, gardening tools, water droplets, and more.
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Symptoms vary but include dark brown spots, yellowing leaves, wilting and leaf loss. You may also find rotting fruit or stalks.
As with most plants, there are a variety of diseases and pests that will keep your tomatoes healthy. By eliminating hornworms, insects, bacteria and viruses, you achieve better yields.
The cause of tomato plant leaves curling and turning black is often related to weather or plant care practices. You can’t stop the rain, but you can change how you care for your tomato plants.
Spider Mite Damage
The fungus Alternaria solani often attacks during the humid or rainy season. Look for black spots on older leaves, often with a bull’s-eye appearance.
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