White Spots on Tomato Plant Leaves: What do they mean?

If you're a tomato gardener, you may have noticed some white spots on the leaves of your plants. These spots can be alarming, but are usually nothing to worry too much about. Essentially, the white spots are a sign of a fungal or bacterial infection. The good news is that there are ways to cure these infections and get your tomato plants back to full health.

This article will discuss what these white spots are, their cause, and ways to cure them. We will also provide tips to help you better care for your tomato plants.

What are the Different Causes of these White Spots?

If you're noticing white spots on the leaves of your tomato plants, it's crucial to determine the cause. Doing so will help you understand how to best treat the issue. In this segment, we will discuss the three most common causes of white spots on tomato leaves.

Let's explore each of them in detail.

Powdery Mildew

One of the most familiar causes of white spots on tomato leaves is powdery mildew. This is a type of fungal infection that affects many different kinds of plants, not just tomatoes. It is more prevalent in humid or wet conditions for an extended period of time.

Powdery mildew usually appears as a white or gray powder on the leaves of infected plants. The leaves and stems may be covered in wild mildew, but since this fungus feeds on the plant's cells, it causes them to turn yellow. This disease gets difficult to avoid as it usually is carried by the wind or insects and can spread quickly to other plants.

If you think your plants have powdery mildew, it's essential to act quickly. It is less likely that this fungus will kill the plant, but it adversely impacts the yield and the taste of the tomatoes produced. And if left untreated, it can become more lethal for the plant.

Sun Scalding

Sun scalding is another common cause of white spots on tomato leaves. This happens when the leaves are exposed to too much sunlight, causing the cells to become damaged. This usually occurs during hot summer days when the sun is particularly strong. The damage appears as white or yellow patches on the leaves. This can eventually cause the leaves to turn white, wither, and fall.

It can happen due to heat damage with a sudden shift of your plant from indoor to outdoor. Not providing support to climbing plants can also cause sun scalding as the leaves then lay flat on the ground, exposing them to more sunlight. If your tomato plant has developed fruits, sun scalding can also impact them. The fruits will have sunken, leathery patches that are white or yellow in color.

If you think your plants have sun-scalded leaves, it's important to provide them with some shade. You can do this by placing your tomato under a tree or using a cloth to cover them. You should also make sure they are getting enough water.

Late Blight

Late blight is a severe fungal disease that can affect both tomato and potato plants. It's a deadly fungal disease caused by the fungus Phytophthora infestans. This highly contagious fungus spreads quickly and can kill the plant within a couple of days.

It is most common in cool, wet conditions and usually appears late in the season. The initial symptoms of this disease are small, water-soaked spots on the leaves. These spots then turn white or gray and become larger. The leaves will also develop a fuzzy mold, eventually turning brown and dying. The stem and fruits of the plant can also be affected.

If the plant has been infected, you will also see brown spots and white mildew appear on the fruits as well. Late blight is so dangerous that if you observe any of these symptoms on your plant, it's best to remove or destroy the plant immediately. This will help prevent the spread of the disease to other plants.

These are three common causes of white spots on tomato leaves. Now that we've explored each one let's discuss some ways to prevent and cure them.

Ways to Treat the White Spots on Tomato Leaves

Now that we have thoroughly discussed the three most common causes of white spots on tomato leaves, we'll explore some ways to treat them.


One way to treat and prevent powdery mildew is by pruning the tomato plant. Doing regular pruning will help improve air circulation and allow the plant to dry out more quickly after watering. It's important to prune infected, and non-infected leaves as the fungus can spread quickly.

You should also disinfect your pruning shears after each cut to prevent the spread of the disease. To do this, you can dip the shears in a mixture of one part bleach and nine parts water.


There are several fungicides that you can use to treat powdery mildew. Sulfur is a common fungicide that is effective in treating this disease. You can find sulfur at most garden stores.

Another option is to make your own fungicide by mixing one tablespoon of baking soda and two tablespoons of horticultural oil in a gallon of water. This mixture should be sprayed on the plant every seven to ten days.

Neem Oil

Neem oil is another effective fungicide that can be used to treat powdery mildew. It's a completely natural product made from the seeds of the neem tree. Neem oil works by preventing the fungus from growing and spreading. It's much safer and more effective than commercial fungicides.

Neem oil is non-toxic, so it would be safe for your kids, pets, and also the environment. Using neem oil also prevents the outbreak of mildew and can heal your tomato plant in about 6 to 7 days.


Vinegar is also an effective fungicide that can be used to treat powdery mildew. Vinegar works by killing the fungus and preventing it from spreading. It's the easiest remedy against mildew as it's available in your house. However, vinegar is acidic in nature, so it's advised not to use it repeatedly.

To make a fungicide from vinegar, mix four tablespoons of vinegar with one gallon of water and spray the mixture on the affected parts.


It may seem like a surprise, but mouthwash can also be used as a treatment against white spots on tomato leaves. Listerine contains alcohol and other ingredients that are effective in killing the fungus. To make this cure, mix one part mouthwash with three parts water and spray it on the plant.

Potassium Bicarbonate

Potassium bicarbonate is widely used in several food-related products and can also be used as a fungicide. It actively prevents the fungus from growing and spreading. You can make a fungicide from this by mixing one tablespoon of potassium bicarbonate with two cups of water and spraying the mixture on the plant.

These are some of the ways you can treat and prevent white spots on tomato leaves. Be sure to try one of these methods the next time you see these spots on your plant. Trying these treatments with a little care and effort, you can keep your tomato plants healthy and free from disease.

Preventive Measures to Avoid White Spots on Tomato Leaves

The best way to avoid white spots on tomato leaves is to take preventive measures. These are some practical measures you can take to keep these spots from appearing are:

Adequate Spacing Between Plants

It's important to space your plants adequately so that they have enough room to grow. Plant your tomatoes about 35 to 60 cm (18" to 24"), keeping in mind the size of your lawn and the type of tomato you're growing. This will help improve air circulation and prevent the spread of diseases.

Proper Watering

You should water your plants early so that they have time to dry out before nightfall. Avoid overhead watering, as this can actually promote the growth of fungi. Water the soil around the base of the plant, taking care not to wet the leaves.


As we discussed above, powdery mildew thrives in humid and shady conditions. One way to prevent this is to provide your plants with adequate lighting. Make sure they get at least six hours of direct sunlight every day.


Pruning your tomato plants regularly is important in preventing the spread of diseases. Remove the dead or dying leaves and stems from the plant. You should also cut off any leaves that are touching the ground.


Mulching your plants helps to retain moisture and prevents diseases from spreading. Use organic mulch, such as straw, pine needles, or shredded bark, around your plants. Be sure to change the mulch every year to avoid the build-up of diseases.


Tomatoes are heavy feeders and need to be fertilized regularly. As fertilizers can be harsh, it's best to use a balanced one and apply it according to the manufacturer's instructions. Be sure to fertilize your plants at the beginning of the season and throughout the growing season.

Plant Resistant Tomato Varieties

Some tomato varieties are more resistant to diseases and fungal infections than others. When choosing a variety, look for ones that are labeled as "disease resistant." Some of the most popular disease-resistant varieties include 'Mountain Pride,' 'Rutgers,' and 'Celebrity.' Planting these varieties will help reduce the likelihood of white spots on your tomato leaves.

Choose Healthy Plants

When buying tomato plants from a nursery, be sure to choose healthy ones. Pick healthy seedlings that have green leaves and are free of pests and diseases. Avoid any plants that show signs of distress, such as yellowing leaves or stunted growth.

By following these tips, you can prevent white spots from appearing on your tomato plants. With a little care and attention, you can keep your plants healthy and free from disease.

Posted by Pavneet Lobana

Pavneet is a home and lifestyle blogger with a passion for creating beautiful and functional spaces. A self-taught chef, she also loves to cook and share her recipes with others. Whether you're looking to create a cozy reading nook or upgrade your kitchen, she has advice that will help you get the most out of your space.