7 Common Diseases That Kill Tomato Plants - Backyard Boss
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7 Common Diseases That Kill Tomato Plants

Tomatoes are a very common fruit to grow in any garden. They taste amazing, and you can use them in many different dishes. So, if you are growing your tomatoes but realize that they are not thriving or growing correctly, they might be affected by one of these common diseases known for killing tomato plants.

Here is a list of the most common tomato killers, how they affect your plants, and how to try to prevent them altogether.

Leaf Spot

Septoria leaf spot on tomato. damaged by disease and pests of tomato leaves
Image credits: Andrey Maximenko via Canva

Leaf spots often affect tomato plants and will start to attack the oldest leaves on the plant and then move on to newer leaves and the stem. You need to watch out for this one because it does not affect the fruit itself. They could look big and red, but as this disease spreads, it will inhibit the fruit from continuing to grow. If it starts early enough, it can stop seeds from growing and blooming.

These spots should be easy to spot, as they appear as small, dark spots on both sides of the leaf. As the disease progresses, these spots will grow larger and start to turn brown.

They will get worse if you leave them in warm and moist conditions. If you want to save some of your plants, you will need to remove all infected plants and leaves from your garden. Make sure to rotate your uninfected plants after removing old, diseased plants so you can not plant in infected soil.

Early Blight

Early blight
Image credits: travenian via Canva

Early blight is the most common tomato and potato disease. Easy blight is a fungus and will severely impact the outcome of your tomato plant-killing off the leaves, stems, and fruit. Early blight comes from fungus, and it survives on dead plants, plant debris in your garden, and other infected plants. High humidity and moist/damp soil are leading causes of early blight.

It will start out looking like small brown spots on the bottom leaves, and as it grows, they will start to look like targets, so ring-like with dry centers that will die out and fall off.

Take care of it right away because it spreads and will kill off your plants, and if you have potatoes close by, they are largely affected by early blight as well? There are two different organic treatments you can use to prevent and fix this. One is Bonide Tomato & Vegetable, and the other is Bonide Liquid Copper Fungicide concentrate. You need to thoroughly spray one of these treatments over the plant, both sides of the leaves, the stem, and the soil.

Late Blight

tomato late blight
Image credits: LianeM via Canva

Late Blight is similar to early blight, it is a fast-spreading fungus, and it occurs during the end of the gardening season and is caused by long, cool rainy periods where the plant is exposed to all of this.

It gives the appearance of frost damage on the leaves, and the spots will look like green-black splotches. The tomatoes will appear to have large brown spots as the fruit begins to die off. The stems will turn black when affected by early blight. There are many strains of late blight that could have different effects on the plant.

Copper spray is a good way to try and control late blight. You can always remove all dying plants and debris from your garden and remove infected soil, before replanting or adding new tomato seeds.

Buckeye Rot

crop rotted
Image credits: Stefano_Carnevali via Canva

Buckeye rot is another form of fungus that can affect your tomato plants and kill them if you’re not careful. It is very common in places where they have high heat and wetter climates.

It appears as small brown spots on both the fruit and the leaves. They will start small but grow larger and form a “buckeye” (concentric rings).

Luckily, buckeye rot is on the easier side when it comes to controlling it and removing it. You will need to remove all diseased tomatoes and keep new seeds away from the infected soil. 

Fruit Rot (Anthracnose)

Unripe tomatoes on plant in the vegetable garden affected by Anthracnose
Image credits: saraTM via Canva

Anthracnose is another fungus that can kill your tomato plants and it is more commonly known as fruit rot. This spreads through “splashing” water, so it happens the most when it is warm and moist out.

This disease looks like small circles indented into your tomato. The flesh outside the skin will start to rot and may rot off completely on overripe fruit.

First, you will want to remove the bottom 12 inches of leaves to make sure the soil does not get infected. After that, make certain to only water the base of the plant, not the leaves.

Black Mold

Molded red tomato
Image credits: unkas_photo via Canva

Black mold is a serious disease for any plant, and it affects tomato plants. It happens at the end of the season after a lot of rain.

It will start out looking like large cuts on your fruit and will be black and have a velvety look to them. These cuts will get bigger as it spreads, and the insides of the tomato will start to be infected.

Fungicides that control Alternaria stem canker can help prevent this from happening if you use them during rainy times. It can also help fix this if you are already infected.

Bacterial Speck

Diseased tomatoes
Image credits: v_zaitsev via Canva

Bacterial speck is a very common disease that affects tomato plants. It happens everywhere in the world, so the climate is not always a factor. When plants are infected with bacterial specks, they will die off, and the fruit will not grow.

It appears as tiny, black spots with a yellow border on the leaves and fruit. The spots may be raised on some spots and sunken in other places.

Unfortunately, there is no cure for this disease. Once it has taken hold of your plant, you will need to remove them. You can prevent it from spreading to your other plants by making sure the uninfected plants do not come into contact with infected soil and water. You will want to waste your hands and any tools that have come into contact with the infected plants because ti can be spread by touch as well.

To Sum Up

Those are 7 common diseases that have been known for killing off tomatoes each year. Luckily you now know what to look for and how to prevent and, in some cases, even reverse them.

You can often stop them completely by keeping an eye on your tomato plants and watering them properly. Also, make sure the soil around your tomatoes is also not infected with any of these diseases since it can also affect your tomatoes.


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