Gardening Basics

How to get rid of tomato blight

October 18, 2011

Tomato blight

Tomato blight is a disease caused by a type of fungus. It appears as brown or white lesions on the leaves and fruits. The spores either spread by water and/or by wind. The disease is contagious in nature and it can infect all the tomato plants along with other plants (e.g. potatoes). Once the disease starts, the infected plants are immediately removed and then all the remaining plants are treated. Potatoes usually show signs of blight first, and then it spreads to tomatoes. If tomato blight is not treated early, it can destroy the whole tomato crop. Gradually stems will also become infected and then it would lead to death of the whole plant.

Causes & Symptoms

Early and late blight, both are caused by a fungus-like mold which thrives in wet conditions like rainy weather, or morning due. It is the same disease that can affect potatoes.

Late blight occurs during late summers and need living tissue to survive. The spores survive in live host plant and attacks when the conditions are suitable. During rains, they can be blown from other infected places and plants. The pathogens act very fast in killing and destroying the plants. A leathery brown spot starts occurring on the fruits during late blight. The leaves will start having watery spots. These spots will start turning brown and a wilted border will occur on the edges. On the underside, spores would be present opposite to the spots in the affected leaves. The stems once affected will have dark brown lesions. White fungal lesions can also occur depending on the damp conditions.

Early blight can occur in any season. It generally occurs in older leaves. Leaves become yellow with occurrence of brown spots and concentric rings. These blights can survive in the plant debris for approx. a year and are soil borne.

How to cure?

1. Once the blight disease occurs, spray a protective fungicide. The usage should be done early. Once the signs start to appear then it gets difficult to control. Organic spray is also a good option for using as fungicide.

2. Clean up the garden area after end of every season. Remove any dead or dying foliage. This will provide over-wintering for the organisms.

3. Stake your tomatoes on planting.

4. Do a regular check up and remove any lower branch that touches the soil.

5. Prune the affected stems. Destroy the stems after pruning as the spores can be present if not destroyed, and can affect the healthy plants by spreading through wind or rain storms.

6. Layer your garden with a good and proper layer of mulch. This will help to prevent the water splashing. Avoid watering your plants directly from above because (makes splashing more likely).

7. While planting, try keeping plenty of space between plants. This will help in reducing infection, provide good air flow and would avoid moisture build up.

8. Avoid growing tomatoes at places there was potato blight last season. Spores rest in dead plant tissues and can affect the healthy ones once the season comes.

9. Watering should be done during early hours in the morning. This will allow the leaves to dry well during the day. Watering should be done only around the base of the plant

10. Once signs are observed in leaves, immediately remove and destroy the leaves at the first sign of blight. Ideal is if the leaves are burned as it will destroy the spores and prevent spreading.

11. Do not add the infected leaves, fruits and stems to your garden compost. This in turn can affect all the other plants.

12. Wash your hands properly after handling the diseased plants. In this way you can avoid infecting the healthier plants.

13. While removing fruits or leaves, put on protective gloves. Check thoroughly all the plants, the leaves and fruits. If only leaves are infected then remove them and destroy, if the entire plant is infected then it’s better to dig up the plant as it will not recover. Use a shovel to dig up the plant. Dig the plants from the roots. One removed, put the plants in a trash bag and dispose off.

14. Use a shear to remove infected fruits. Dispose the infected fruits in a trash bag.

15. Get blight-resistant varieties.


A. Can we save the seeds saved from infected tomatoes?

Normally, the pathogens are not carried in the seeds. If the infected fruits start to rot before seeds are matured, then it’s better not to harvest.

B. Can we eat tomatoes if the plants get late blight?

We can eat but the fruits should not be stored.

C. How does the disease spread?

The disease spreads by spores. The mode of transmission for short distance is by rain and for very long distances, it’s by wind.

Things to avoid

1. Eradicate host plants

2. Plant your tomatoes every year at different locations.

3. Plant the tomatoes away from potatoes.

4. Don’t save seeds from infected fruit.

5. Check the tomato plants before buying (for any sign of disease).

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