Septoria Leaf Spot Treatment To Save Your Tomatoes

Septoria leaf spot is likely the most common disease found in tomato leaves. It is spotting you might find on the lower part of the leaves.

Because of this disease, some of the leaves would turn into a yellow color or start falling off the stem. If your garden has this issue, you do not have to worry because it is fixable.

However, it is not only the problem of tomato plants. It may pop up in other areas.

In this article, you will find the way to deal with septoria leaf spot, the best treatment for it, how they spread, the symptoms and diagnosis, and some other things.


What is Septoria Leaf Spot?

Septoria leaf spot is caused by a fungus, Septoria lycopersici. It is one of the most destructive diseases of tomato foliage and is particularly severe in areas where wet, humid weather persists for extended periods.
Septoria Leaf Spot

In simple words, it is a tomato leaf spot. It is a very common problem that pops up on the plants. Septoria lycopersici is a fungus that causes this disease.

Septoria leaf spot can affect the Solanaceae family plants like tomatoes, potatoes, and eggplants around the world. Because of this disease, the plantations can be weakened and defoliated quickly.

So, it will be hard for the plant to produce fruits. This fungus is considered the most damaging tomato diseases. Even though it is not the deadliest disease, it still gives a bad effect on your garden.

Lots of fungi come from the Septoria genus. They are over 1.000 species out there. However, the most essential thing is knowing how to deal with the disease.

How Septoria Leaf Spot Spreads

Septoria leaf spot usually appears on the lower leaves after the first fruit sets.
Tomato Blight

Fungus Spores like Septoria lycopersici are quite clever when it comes to hiding. They will wait for the right time with ideal conditions for them.

Besides hiding out, the Septoria can travel great distances to find that ideal condition.

They linger and survive in the infected plant debris on the ground surface. The fungus can overwinter too.

The wind and water splash can be the cause of spores that stays on the lower leaves. Besides, insects can also carry them accidentally.

Thereupon, there is spotting on the leaf surface. It would be grey in the center and a little bit brown on the edges.

The lesions center contains something called pycnidia. It is the fungus fruiting bodies that become the location where spores are from.

Further, it will damage the lower leaves. Then, it would get severe and fall from the branch to the ground surface.

After that, the pycnidia would get inside the soil and wait for the right time to get back to the leaves of the plants.

This one could happen because of water splashes, insects, wind, or even tools or human hands.

Indeed, the best condition for the fungus is during the summer and spring seasons. During fall and winter, this septoria leaf spot will not be a problem for your garden.

Symptoms of Septoria Leaf Spot

Symptoms appears at the edge of tomato leaves, with dark, damaged plant tissue that spreads through the leaves toward the stem.
Tomato Blight Image

There are some septoria leaf spot tomato symptoms you need to pay attention to. So, you can get rid of them to keep the plants healthy.

This disease starts somewhat circular. It would first appear right on the underside of the lower leaves.

The size would be very small, about 1/16 to 1/8 inches in diameter. It appears to be dark brown on the edge.

Moreover, the center would be tan or light gray. You will also find the yellow halo surrounding the spot.

The Septoria leaf spot would start to develop with larger brown spots on tomato leaves. Some of the themes can even merge.

Use a magnifying lens to see the core of the fungus body. It looks like some pimples with dark brown color. That is what differs this disease from the others.

As we know, the symptoms usually happen in the lower leaves. However, it has got a lot of chance to grow during the growth of tomato plants.

It is not always on the leaves, you may also find it on the stems, blossoms, and calyxes.

One good thing about this fungus is that you will not find it infecting the fruit itself. Well, it is still important to treat the septoria leaf spot because it would make the plant weak.

Further, when the plants have the leaves falling off the stem, they will not be productive anymore.

You might not get the mature tomatoes from your garden. These spotting diseases will spread quickly when untreated. So, you have to know the right septoria leaf spot treatment.

On other plants, the difference would be on the initial color and the size of the spots. For example, the reddish spore will form on soybeans. In pistachio trees, the spotting comes in brown colors.

Septoria Leaf Spot Treatment

Remove infected leaves immediately, and be sure to wash your hands and pruners thoroughly before working with uninfected plants.
Septoria Leaf Spot Treatment

When it comes to treatment, people would tend to go with the most practical and simple ones. Well, you should choose the one according to the condition of the plants themselves.

If your tomato plants already have the septoria leaf spot, there are some methods you can choose to treat and get rid of them in the future. These techniques include:

  • Using Organic Fungicide

With organic fungicide, you can prevent the spreading of the spotting. The product should consist of either potassium bicarbonate or copper.

Therefore, you have to spray the solution immediately after you see the first symptoms.

  • Removing Infected Leaves

It is a simple method. When you find some leaves with the fungus, just remove them all as soon as possible.

Before that, you have to wash the hands and pruners cleanly. It would reduce the chance for a new form of spores to get on the plants again.

  • Using Chemical Septoria Leaf Spot Fungicide

This one has to be the last option that comes to your mind. Chemical product is not an ideal choice to control the infections.

However, there is one recommended product that you can buy. You can choose either Fungonil or Daconil. They are the most effective and least toxic.

Septoria Leaf Spot Prevention

Organic fungicides can go a long way towards treating and preventing fungal infections like septoria leaf spot.
Prevent Septoria Leaf Spot

Prevention is better than cure. In this case, you should have some plans or strategies to prevent the Septoria leaf spot diseases from popping up in your garden. Here are things you can do.

  • Remove All Fallen Plant Debris

It is important to keep the debris away from the soil. As soon as you see some fallen leaves, you have to eliminate all of the litter.

Those leaves can be a good shelter for the spores to keep them alive during winter. Before cleaning the garden bed, you need to wash the hands and tools you use for the job.

  • Check the Weeds Regularly

Keeps them in check. The solanaceous weeds can carry fungal spores. If they are infected, it has a great chance to infect other plants nearby.

  • Mulch Around The Plants

Doing this would prevent the soil from splashing up and spreading the spores to the plant. Besides, this method would also reduce the development of weed.

Additionally, the mulch is very helpful to be an aid in water retention for the soil.

More Prevention Methods

Septoria leaf spot begins as tiny black dots on the leaves, enlarging to small circular spots with a dark margin and gray center.
Controlling Septoria Leaf Spot
  • Rotate the Crops

The diseased weeds, plant debris, or perennials would be a good place for Septoria fungi to live for up to 3 years. The crop rotation might help to deminish the reinfection chance.

  • Apply Water to the Soil, Not the Plants

This way will reduce the likelihood of spore spread. As an alternative, you can use a soaker hose right at the plant base to keep the leaves dry. Water it in the morning only.

  • Get Rid of Pests

If you keep the pasts at bay, you will also reduce the spore transmission. It is because they may carry spores accidentally from one plant to other plants.

  • Trim Excess Foliage

This way helps provide better airflow for the plant. Ensure that it gets proper airflow. If you have it tightly packed, the risk of diseases can be high.

  • Choose Other Plants

While tomatoes have a high chance to get septoria leaf spots, you should opt for other plants that are resistant to these diseases.

Frequently Asked Questions

Septoria leaf spot usually appears on the lower leaves after the first fruit sets.
Septoria Leaf Spot Tomato

Q: Are tomatoes from infected plants edible?

A: Yes, they are edible. Generally, the septoria leaf spot only affects the leaves and sometimes the stem. Usually, the fruit is intact.

Well, you might find tomatoes with spotting. Do not worry, it is likely not septoria fungi because it does not affect the fruit.

Q: Can you cure the Septoria leaf spot?

A: Most spotting diseases caused by fungal can be treated. If you have good management, you can reduce the potential of fungal spread.

You can apply some treatments above but it would not heal the existing damage. They would prevent the spreading of the spores.

Some leaf spots caused by bacterias are not treatable. The best thing to deal with it is to remove the infected materials and apply the treatments.

Therefore, you can control and eliminate any leaf spots your plants have.


Dealing with Septoria leaf spot on tomatoes or other plants can be done by applying simple methods. You cannot cure the infected leaves but you can prevent the spreading.

So, your plants can grow healthy and produce great quality fruits.

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