Identifying And Controlling Septoria Leaf Spot


Classified as a serious fungal disease, Septoria leaf spot is one of the most common destructive diseases which normally attack tomato plants

If you notice your tomato plants’ lower leaves are losing their color, your plants turning yellow, or falling, there is a possibility your plant has been attacked by this fungal disease caused by the fungus Septoria lycopersici

septoria leaf spotseptoria leaf spot

This plant disease is very destructive. It is extremely severe in areas with high humidity and where wet weather lasts for prolonged periods. 

Like early blight, the disease occurs first on the lowest plant leaves and overwinters. 

If left untreated, the fungus may cause the total defoliation of lower leaves or, in extreme cases, death of the plant.

What is Septoria Leaf Spot?

Septoria leaf blotch or sport may attack the plant at any phase of the plant’s life cycle. 

The tomato crop is the most vulnerable to the disease. 

The good news is the disease is easily identifiable. 

A diseased plant will begin exhibiting brown spots with light tan to gray centers. 

The brown spots or dark brown margins on the plant are one of the most common symptoms of septoria leaf spot. 

As the spots mature, they start developing small black fruiting bodies in the center. 

Once the bodies ripen, they explode and spread more spores.

What Damage Does Septoria Leaf Spot Cause?

This fungus doesn’t live in soil but on the plant. On the tomato crop, the disease makes the leaves of the plant fall off. 

With reduced foliage, the health of the tomato will suffer as it will be able to gather energy from the sun. 

Once the disease progresses, it infects all the leaves and makes them wither and die.

How to Control Septoria Leaf Spot

Controlling the septoria leaf spot requires some time, but it is indeed manageable. 

There are some pest management strategies that home gardeners may follow to get rid of the plant disease.

Remove Diseased Leaves

Remove diseased leaves: The first step which you must do is to remove, and later destroy or burn, all the infected leaves during the growing season to curb the growth of the fungus. 

At the end of the season, dispose of or bury the foliage from the diseased plants.

Mulch Around the Base of the Plants

Mulch around the base of the plants: Mulch is an important matter which prevents soil splashing up onto the leaves. 

This is likely to prevent the spread of spores to your plant. 

A 3″ to 4″ inch layer of mulch will also help in increased water retention which will be an added benefit for the plant in preventing disease development.

Water the Soil

Water the soil: Many home gardeners make this mistake when watering the plants. Instead of watering the soil, they end up spraying the plants. 

The likelihood of spore spread is more in wet leaves. 

Instead of using overhead watering, use drip irrigation or soaker hoses to reduce the extent of leaf wetness.

Fight Against Pests

Fight against pests: Different pests carry spores and transport them from one plant to the plant. 

To reduce spore transmission, it is important for you to reduce the pest population.

Keep Weeds In Check

Keep weeds in check: Some solanaceous weeds are notorious for harboring fungal spores. 

The fungus is found in jimsonweed and horsenettle and other plants in the Solanaceae or nightshade families. 

The infected weeds will spread the disease to nearby plants. 

This is why it is important to reduce the weed growth to save your plant from the fungal attack.

Rotate Crops

Rotate Crops: Since the fungus survives in infected plant debris, perennials, or weeds for a period of 3 years, only crop rotation can reduce the possibility of reinfection every year.

Improve Air Circulation

Improve air circulation: If you can handle the plant without breaking them, raise them off the ground and allow the faster drying of foliage.

Space plants for good air circulation.

Use of Fungicides

Use of fungicides: You may adopt non-organic treatment to get rid of the septoria leaf spot. 

Even though commercial fungicides are not effective in curing the disease, they can prevent it from spreading. 

The application of Maneb, mancozeb, chlorothalonil, or a copper-based fungicide such as copper sulfate is essential in treating the disease. 

NOTE: Do Not Use copper on eggplant.

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The fungicides do not only fight against tomato diseases but are also effective against other diseases such as late blight, gray leaf spot, and early blight

Before you carry out fungicide sprays, do read the label directions and be mindful of all the precautionary measures mentioned in the product.

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