White Spots on Tomato Leaves | Causes, Treatment & Prevention

Tomatoes are very susceptible to pests and diseases. Many of these issues show symptoms like white spots on leaves, wilting, and diminished overall plant growth, which often leads to the downfall of the entire crop. 

Quickly determining the cause of the foliage discolouration is pivotal in the health of the plant and its yield capabilities. The following article describes the scenarios that cause white spots on tomato leaves, along with treatment and prevention techniques. 

Causes of Whites Spots On Tomato Plant Leaves

There are many fungi, bacteria, and pests that cause stress to tomato plants, but only a few cause white spots on their leaves. While white spots might not be their only symptom, the following four infections are the most frequently diagnosed when dealing with this problem.  

Powdery Mildew

Powdery mildew is the most common cause of white spots on tomato leaves. It is caused by several different genera of fungi that are commonly found in nature. They need a live host to survive and reproduce. The fungi favour high temperatures, high night-time humidity, and low daytime humidity, which often develop during the spring and fall. 

How Does Powdery Mildew Get on Tomato Plants

Tomato plants need at least 6 hours of daily sunlight, consistent temperatures above 60 degrees Fahrenheit, adequate water, nutrient availability, and lots of air circulation. If these conditions are not met, then the tomato plants might experience stress that leaves them susceptible to powdery mildew. 

Powdery mildew will not usually kill the tomato plants but will stress them enough to diminish their yield capabilities. Some believe the tomatoes from the vines infected with powdery mildew taste differently. 

Tomato Plants with Late Blight

Tomato plants with late blight will experience severe leaf damage, infected fruit, and plant death if left untreated. Leaves will show small whitish bleached spots that grow into larger black blotches that resemble frost damage. It’s often accompanied by a fluffy white growth on the underside of the leaves. If left untreated, the fruit will rapidly become blotchy, foul-smelling, and inedible. 

Causes of Late Blight

Late Blight in tomato plants is caused by the fungus Phytophthora infestans, which usually occurs during extended periods of cold and rainy weather or heavy dew. Most often occurring during the late summer or early fall. 

Preventing Late Blight

Prevent Late Blight by giving ample room to each tomato plant, allowing sunlight and air to reach the lower stems. Use ground watering techniques to limit the amount of water left on the leaves. Wait until your plants are dry before working with them to limit the chances of spreading the microorganisms that carry the fungus. 

Septoria Leaf Spot Disease 

Septoria leaf spot caused by the fungus Septoria lycopersici is a common tomato disease that starts off by causing small white spots with dark edges. Most often occurring during extended periods of warm and rainy weather during the mid to late summer.

Preventing Fungal Infections

There will be instances when fungal infections are inevitable because there are countless spores that naturally occur in the environment; and, when the conditions become ideal, it can be difficult to keep them from germinating. Keeping your tomato plants healthy with daily water checks and weekly fertilization treatments will boost the tomato plants’ defence capabilities. Proper care, along with the following few tips, will help prevent fungal infections in tomato plants.

• Leave enough space around the tomato plants to allow adequate air circulation.
• Use ground watering techniques like soaker hoses, and don’t work in your plants while they are wet. 
• Prune the lower branches near the soil that naturally carry fungal spores.  
• Preventatively treat the leaves with an all-natural essential oil spray at least twice per season. 

Sun Scalding

Sun scalding symptoms include the presence of blotchy white and yellowish spots all over the plant’s leaves and fruits. Damage from sun scalding will occur on the top, most exposed, parts of the plant. If conditions continue, then the leaf’s colour will begin to bleach, appearing papery and white, especially along the leaf edges.  

Causes of Sun Scalding

Sun scalding is a physical condition that is caused by overexposure to the sun’s ultraviolet rays. The plant gets sunburnt! Sun scalding can occur on the tomato plant’s leaves but is most damaging when on its fruit. 

How to Prevent Sun Scalding

Tomato seedlings are particularly vulnerable to sun scald damage. Be eyeful for symptoms of sun scald and move the plants into the shade if they begin to show any signs. Making sure the tomatoes are planted in the ideal location is the best prevention of sun-scald. They need at least 6 hours of direct sunlight and prefer temperatures near 75 degrees Fahrenheit. If they receive too much sun but cannot be transplanted, then install a sunshade that would give the plants relief during the hottest part of the day. 

How to Get Rid of White Spots on Tomato Plants

Fungal infections such as Late Blight and Septoria Leaf Spot can easily be managed by a simple fungicide. Always read the label and use it as directed. Using Integrated Pest Management (IPM) is the best way to manage your tomato plants. IPM techniques would consist of providing fertilizer to help the plant’s immune system, removing infected stems or plants, using a natural fungicide, followed by a chemical fungicide if the infestation is severe enough. 

Best Treatment for White Spots

The best treatments are those that are implemented early. There are several all-natural products and remedies that do a great job of preventing or treating small infestations of fungi, mildews, and pests that feed on tomato plants.

Natural remedies for powdery mildew

Neem oil is a popular natural product that is documented to prevent and treat a wide array of infections including powdery mildew, early and late blights, and leaf spot diseases. Neem is also great as a natural insecticide for pests like spider mites, weevils, and tomato beetles. Neem oil can be used as a preventative or treatment. 

Neem oil is often found in pre-mixed bottles that contain other essential oils like lemongrass, eucalyptus, and lavender. These natural remedy products work great against fungal infections and can be found at your local grow store!

Be Aware

Neem oil makes leaves very photosensitive and should only be applied when direct sunlight is no longer on the plant for at least 12 hours or else leaf damage is likely to occur. Neem oil is commonly found in a concentrated form and must be properly diluted otherwise it will do tremendous damage to your plant. 

Homemade Baking Soda Spray for Tomatoes

Baking soda natural remedies work by coating the leaves with sodium bicarbonate, which alters the pH on the surface of the leaves enough to inhibit the growth of fungal spores. Add 2 teaspoons of baking soda to 1 gallon of water and mix with oil. The oil acts as a surfactant that adheres the baking soda mixture to the leaves. Horticultural oil is often suggested but is labelled as a pesticide due to its chemical additives, so use cottonseed oil and soap if you want to make an effective natural alternative. 

Removing Tomato Leaves with White Spots

Removing the tomato plant’s leaves that have white spots is usually recommended as long as you never remove more than a third of the leaves at one time, which could stress the plant enough to kill it. 

Powdery mildew 

It is recommended to remove the leaves infected by powdery mildew if the infestation is caught early. If the powdery mildew infestation has covered the entire plant, then treatment through essential oil sprays would be more effective. 

Late Blight

It is recommended to remove tomato leaves infected with late blight fungus only if it is identified early. Once it progresses to over half the plant, then it would be best to remove the entire plant so that it doesn’t spread to the rest of the garden. Remove infected leaves to limit spread and increase air circulation while preventatively treating them with an essential oil spray. 

Septoria Leaf Spot 

It is recommended to remove the leaves that contain leaf spots caused by Septoria leaf spot disease. Be sure to bag them and throw them away. Don’t compost the infected plant material because it could respread to your plants if you use the compost later. Since the spores attach to the plant when water is splashed from the soil onto the leaves, many master gardeners will remove the lower third of their tomato plants during the vegetative stage to prevent the common fungus from colonizing. 

Sunscald

It is recommended to remove leaves damaged by sunscald only if the damage is minimal. If the damage is severe, then the plant will probably not survive. Seedlings can be saved by removing the burnt leaves only if there is at least 50% of the leaves left undamaged. Note that removing leaves will allow more sunlight to enter the inside of the plant which can lead to further sun scalding of leaves and fruit. 

Stopping the Spread of White Spots on Tomato Plants

The removal of entire tomato plants is sometimes necessary to stop the spread of white spots to other uninfected tomato plants. To stop the spread of white spots on a single plant, you must remove the infected foliage, treat it with a fungicide or essential oil spray every 10 days, apply a soil fertilizer, and monitor the plants closely. 

Keeping the growing conditions as close to ideal as possible will increase the likelihood of the tomatoes surviving the infestation causing the foliage’s white spots. 

Eating Tomatoes from Affected Plants

In most cases, if only the tomato plant’s leaves contain white spots, then the harvested tomato fruit is likely safe to eat. If the tomato fruit contains white spots, then some other infection or infestation is occurring, and the tomato might not be safe to eat. 

Powdery mildew

Tomatoes from plants infected with powdery mildew will still be safe to eat but are commonly said to have a changed flavour. 

Late Blight

Tomatoes from the plants infected with late blight can still be edible but only if the infestation wasn’t severe. Many cases of late blight cause the plant to die before the fruit has ripened, leaving it to rot and become unusable for consumption.  

Septoria Leaf Spot

Tomatoes from plants infected with Septoria leaf spot disease are usually still safe to eat because the fungus rarely infects the fruiting part of the plant. If the infestation is severe, then the development of the fruit might stop, causing under-ripened, unappealing tomatoes. 

Sun Scald 

Tomatoes from plants damaged by sun scalding will still be safe to eat, but if the fruit itself is sun scalded, then it will not recover. It should be removed and thrown away to prevent attracting other pests to the garden. 

FAQ White Spots On Tomato Plants

Verdict: Tomato Leaves with White Spots

Powdery mildew, Late Blight, Septoria Leaf Spot, and sun scalding are the most frequently diagnosed issues that cause white spots on tomato plants. Powdery mildew is the most common cause of white spots on tomato leaves, and sun scalding is the most permanently damaging. The best treatments are those that are implemented early and include fertilization and applications of all-natural oils. Keeping your tomato plants healthy with daily water checks and weekly fertilization treatments will boost the tomato plants’ defence capabilities. In most cases, if only the tomato plant’s leaves contain white spots, then the tomato is likely safe to eat, but if the tomato contains white spots, then some other infection is occurring, and it might not be safe.