Late Blight of Tomato- How to Treat the Disease - No Plant No Life

Sunday, January 22, 2023

Late Blight of Tomato- How to Treat the Disease

Tomato Late Blight is a serious fungal disease that can wreak havoc on tomato gardens. This disease is triggered by the fungus Phytophthora infestans, which causes unsightly brown or black spots to appear on the leaves, stem, and fruit of tomato plants. 

Without prompt intervention, the disease can spread rapidly, wiping out the entire tomato harvest. In this blog, we'll delve into the underlying causes and symptoms of Late Blight, as well as the preventive measures and treatments to keep your tomato plants strong and bountiful.

Time is of the essence in stopping the spread of this disease and safeguarding your tomato garden from devastating harm. Want to know how to battle Early Blight in tomato plants as well? Check out this resource!

Causes of Late Blight Disease

Tomato Late Blight is a fungal affliction caused by the water mold Phytophthora infestans. This mischievous fungus can infiltrate your tomato plants through their leaves, stem, and fruit. 

It can travel by wind, rain, and even by hitching a ride in irrigation water. This fungus flourishes in cool, humid conditions, so it's crucial to be mindful of the atmospheric conditions that play into its growth.


Environmental Conditions that Favor the Spread of the Disease.

Tomato Late Blight pathogen thrives in temperatures ranging from 60-77°F (15-25°C) and in moist environments. The disease spreads with astonishing speed in rainy weather and when the leaves of the plants remain wet. It's also prone to spreading in cramped quarters.

To defend against the spread of Late Blight, it's vital to be cognizant of the conditions that encourage the fungus to flourish.

In high-risk areas, the best course of action is to plant your tomatoes in a spot with ample airflow and steer clear of overcrowding.

You should also steer clear of overhead irrigation and clear away any debris or weeds that may serve as hiding spots for the fungus.

Being well-informed about the root causes of Late Blight is key in preventing and combating this disease. The fungus Phytophthora infestans is the mastermind behind this malady, and it loves to lounge in cool, humid conditions.

Understanding the causes of Late Blight disease is crucial in preventing and treating the disease. The fungus Phytophthora infestans is responsible for the disease and thrives in cool and damp conditions. 

By being vigilant about the conditions that give the fungus an advantage and taking preventative measures, you can safeguard your tomato garden from the devastation of Late Blight.

Description of the Visual Symptoms in Tomato Plants

  • The first signs of Late Blight disease are typically dark, water-soaked spots on the leaves of the tomato plant. These spots will often have a bull's-eye pattern, with a dark ring around the edge and a lighter center. 
  • As the disease progresses, the spots will grow larger and turn brown, and the leaves will begin to wilt and die. 
  • The fungus can also infect the fruit of the tomato plant, causing dark, sunken spots on the skin of the tomato. These spots will often have a concentric ring pattern and will be accompanied by a slimy, foul-smelling ooze. 

Identification of the Early Signs of the Disease

  • One of the key ways to identify Late Blight disease early on is to keep an eye out for the dark, water-soaked spots on the leaves of the tomato plant. These spots will often appear first on the lower leaves of the plant and will spread upward as the fungus is slowly creeping up on your tomatoes!
  • Another early sign of the disease is the wilting and dieback of the leaves of the tomato plant. If the leaves of your tomato plants are wilting and dying, despite adequate water and care, it could be a sign of Late Blight disease. 
  • Additionally, if you notice any dark, sunken spots on the skin of your tomatoes, or a slimy, foul-smelling ooze coming from the fruit, it is likely that your tomatoes are infected with Late Blight disease.

If you suspect that your tomato plants have Late Blight disease, it is important to take action as soon as possible to prevent the spread of the disease. 

This may include removing infected plants, applying fungicides, and practicing good crop rotation and sanitation practices. 

It is also important to always keep an eye out for the early signs of the disease so that you can take action before it spreads too far.

Prevention of Late Blight Disease

Tomato Late Blight disease is a serious problem for tomato growers, as it can cause significant damage to crops and lead to significant yield loss. 

Below are some of the steps you can follow to prevent Late Blight occurrence and outbreak in your tomato garden. 

1. Choosing Disease-resistant Tomato Varieties

One of the most potent ways to fend off tomato Late Blight is by selecting tomato strains that are naturally resistant to the disease.

These tomato varieties, specifically bred to withstand Late Blight, are less susceptible to the disease and can greatly reduce its impact on your crop.

As you select a disease-resistant tomato variety, make sure to look for strains that have been rigorously tested and proven to be resistant to Late Blight.

A few of the most popular disease-resistant tomato varieties include:

2. Proper Planting and Care of Tomato Plants

In addition to selecting disease-resistant tomato varieties, proper planting and care of tomato plants are also crucial in preventing Late Blight disease. 

This includes planting tomatoes in well-draining soil, in a location that receives plenty of sunlight, and providing them with proper irrigation and fertilization. 

It's also important to space the plants appropriately to allow for good air circulation, which will help to prevent moisture build-up on the leaves. 

3. Crop Rotation 

Another important step in preventing Late Blight disease is crop rotation. This involves rotating the location where you grow your tomatoes each year so that the disease-causing spores do not build up in the soil. 

This can greatly reduce the chances of infection and should be an important part of any tomato grower's disease management strategy. 

4. Using Clean Seeds and Seedlings

Lastly, using clean seeds and seedlings is another important step in preventing Late Blight disease.

This means using seeds and seedlings that have been certified to be free of disease-causing spores, as well as taking care to ensure that your seedlings are not contaminated by spores from infected plants. 

By taking the steps discussed above and choosing disease-resistant tomato varieties, you can greatly reduce the chances and possibilities of your tomato crop being affected by Late Blight disease. 

Remember that it's always better to prevent than to treat, so take the necessary precautions to protect your tomato plants. 

Treatment of Late Blight Disease 

Tomato Late Blight disease is a grave concern for those who cultivate tomatoes, as it can cause severe harm to the crops and result in a significant reduction of yields. Below are some ways to handle tomato Late Blight disease, focusing on various treatment options.

1. Utilizing Fungicides

One of the go-to solutions for treating tomato Late Blight is through the use of fungicides. These chemical compounds serve to destroy or suppress the growth of fungal pathogens, like the one causing Late Blight.

With numerous types of fungicides on the market, it's imperative to pick one that's specially designated for use on tomatoes and to control Late Blight.

Additionally, it's vital to strictly adhere to the label instructions and to properly apply the fungicides at the appropriate time and in the right amount for maximum effectiveness

2. Eliminating Infected Leaves and Plants

Another crucial step in handling tomato Late Blight disease is to eliminate infected leaves and plants as soon as they are identified. 

This is because the spores of the fungus that causes the disease can spread rapidly, and by eliminating infected leaves and plants, you can aid in preventing the disease from spreading to other parts of your tomato plants or to nearby plants. 

3. Using Copper-based Fungicides 

Copper-based fungicides are another option for treating tomato Late Blight disease. Copper-based fungicides work by creating a barrier that prevents the fungus from penetrating the tomato plant's leaves and stem. Copper-based fungicides are also effective in controlling many other fungal and bacterial diseases. 

4. Natural Alternatives 

Lastly, there are also natural alternatives to treating tomato Late Blight disease. These include using neem oil, which is derived from the neem tree and has been found to be effective in controlling fungal pathogens.

Garlic spray and baking soda solution are also known to be effective in controlling fungal diseases. 

It's important to note that the most efficient way to control Late Blight is to prevent it from happening in the first place. 

This includes utilizing disease-resistant tomato varieties, practicing proper planting and care of tomato plants, crop rotation, and using clean seeds and seedlings. 


In conclusion, tomato Late Blight disease is a major concern for tomato growers and can cause severe harm to crops and substantial crop losses.

To tackle this disease, it is important to take preventive measures such as choosing disease-resistant tomato varieties, providing proper care and maintenance, implementing crop rotation (because variety is the spice of life, even for plants), and using clean seeds and seedlings.

In case of an outbreak, treatment options include using fungicides, removing infected leaves and plants, using copper-based fungicides, and natural alternatives.

Early detection and treatment are crucial in preventing the spread of the disease and minimizing the impact on your crop.

Regular monitoring and inspecting of the plants for symptoms of Late Blight disease can help to catch the infection early and take appropriate action.

For Further Information 

For further information on Late Blight disease and tomato plant care, it is recommended to consult with local agricultural extension offices, agricultural universities, research institutions, or online resources such as the National Gardening Association or the American Phytopathological Society. 

Also, you can refer back to this blog post whenever you feel stranded. Go treat your plants and restore natural beauty to your garden!

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