brown spots on tomato leaves

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The brown spots on tomato leaves are caused by a variety of factors, including pests, disease, and environmental stressors. Among the most common culprits are fungal diseases like Septoria leaf spot and early blight, both of which can cause extensive damage to the foliage of tomato plants.

In addition to these diseases, pests like aphids and thrips can also cause brown spots on leaves by sucking the sap from the plants or feeding on them.

Here in this post, I will discuss Septoria leaf spot disease.

You can read more about 9 Deadly Tomato Pests That Can Ruin Your Tomato Yield here.

Identifying and Controlling Septoria Leaf Spot

Septoria leaf spot is a fungal disease that can affect a wide range of plants. The fungus that causes these spots are called Septoria lycopersici and it is commonly found in the soil.

The disease affects tomato plants and leads to the formation of brown spots on the leaves. The spots are circular and have a yellow halo around them. The fungus can also cause the leaves to turn yellow and drop off the plant.

To control septoria leaf spots, it is important to identify the symptoms early and take action to prevent the spread of the disease. It is a fungal disease that affects the tomato leaves(especially the bottom leaves of the plant), but not the fruit.

How Septoria Leaf Spot Spreads:

This fungus can infect a plant through wounds in the leaves or stems, and it can also be spread by water or wind.

Each leaf spot produces hundreds of fungal spores that can be splashed or blown onto other leaves, resulting in even more leaf spots.

Under favorable weather conditions, these new leaf spots produce more spores.

Symptoms of Septoria Leaf Spot on Tomato Plants

Septoria leaf spot is a common plant disease that can affect both home gardens and commercial crops. This infects tomatoes and other members of the Solanaceae family.

Symptoms of septoria leaf spot include small, brown lesions on the leaves of affected plants. These lesions may eventually coalesce and cause the leaves to turn yellow and drop off. Infected fruits may also develop brown spots.

How to Treat Septoria Leaf Spot

It is very difficult to treat the leaves that are already affected by the fungus. Your best bet would be to remove the affected leaves or the whole plant (if most of the leaves are infected) so that rest of the plants in your garden do not get affected.

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Preventing diseases from happening is rather a simple process.

How to prevent Leaf spot diseases in tomatoes:

Tomato leaf spot is a fungal disease that can reduce yields and cause significant damage to the fruit. They are quite common in tomatoes. However, you can prevent them from occurring by following some simple steps.

Cover the soil below the tomato plants with mulch:

The best way to treat the Septoria leaf spots is to cover the soil below the tomato plants with mulch. This will help to prevent the spread of the disease and also protect the plants from further infection.

Don’t pour Water on the leaves:

The best way to prevent the disease is to water the soil, not the leaves. This will help to keep the foliage dry and reduce the chances of the fungus spreading.

If the disease does occur, remove any affected leaves as soon as possible. This will help to prevent the fungus from spreading further.

We discussed the ideal watering technique for plants in this post, go and read it first if you haven’t done it already.

Use Stakes or trellis To support your tomatoes:

Trellising tomatoes can help to prevent tomato leaf spot diseases. By using a trellis, the plants are able to grow more upright, giving them a better chance of avoiding disease.

Furthermore, by staking the plants, you create an elevated area for them to grow above the ground, which also helps to avoid disease.

Read more about the tomato support system here.

Don’t work in tomato plants when the leaves are wet:

When leaves are wet, they are more susceptible to disease and fungi. Working in wet tomato plants puts workers and plants at risk for these diseases and fungi.

Make sure you have good air circulation around the plants:

Air circulation is important for preventing leaf spot diseases. If air circulation is restricted, fungal spores can accumulate, leading to disease.

This can be done by spacing the plants far enough so that they don’t share the same air circulation path, using natural or artificial ventilation, or using a greenhouse.

Use Crop Rotation methods:

From a soil science perspective, rotating crops is an effective way to manage pests and promote crop health. By alternating the use of different plants in the same field, you can control which plants are targeted by pests and which plant nutrients are available to the rest of the crop.

In addition, rotating crops helps reduce soil erosion and increases the stability of the soil structure.

Should you use a fungicide?

Most home garden tomatoes do not need to be treated with a fungicide. In fact, treatment with a fungicide can actually lead to problems such as toxicity, resistance development, and decreased fruit yields.

You can read more about the devastating effects of applying fungicides in your garden here.


In conclusion, Septoria leaf spot disease on tomatoes is a serious issue that can cause extensive damage to tomato plants. The disease can be prevented by using organic methods, It is also important to catch the disease early and address it immediately.

I hope this post was helpful to you. You can read a ton of tomato-related articles here.

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