If you’ve ever grown tomatoes, you might agree that they aren’t too difficult to grow. Still, plants can generally be finicky, and tomatoes are no exception. Everything can be going right, your tomato plants are healthy, dark green, and producing tons of fruit – then next thing you know, there are weird, white spots showing up on your tomato leaves.
So, what are these white spots, and what do they mean for your tomato plants? Many gardening issues are solved through a process of elimination, which will probably be no different here. Let’s discuss three possible reasons for white specks or spots on tomato leaves and what to do about each situation.
1. Late blight
What is late blight?
Late blight is a fungal disease that affects both potato and tomato plants. The disease is caused by the pathogen Phytophthora infestans, which thrives in wet, humid conditions. Late blight can cause extensive damage to crops and, in some cases, can lead to plant death.
How can I prevent late blight?
You can do a few things to prevent late blight on your tomato plants. Make sure to water your plants at the base of the plant rather than from overhead. This will help reduce the amount of moisture on the leaves, making it harder for the fungus to spread.
Avoid working with your plants when they’re wet. This includes watering them and picking fruits or vegetables from the plant. If you must work with wet plants, be sure to disinfect your tools before using them on healthy plants.
Remove any affected leaves or fruits from the plant as soon as you see them. This will help prevent the fungus from spreading further.
What does late blight look like?
Late blight typically appears as dark brown, white, and black spots on the plant’s leaves. The spots may also appear on the stems and fruits of the plant. The entire plant may turn brown or black and die in severe cases.
When does late blight happen?
Late blight typically occurs during wet, humid weather conditions in late summer or early fall. However, it can also occur during warm, dry weather periods if there is enough moisture on the plant leaves.
2. Powdery mildew
What is powdery mildew?
Powdery mildew is a type of fungus that affects a wide range of plants, including tomatoes. The fungus grows on the plant’s surface and produces a white or light gray powdery substance. Powdery mildew can weaken the plant and reduce its ability to produce fruit. In severe cases, the plant may die.
How can you prevent powdery mildew?
- Make sure to water your plants at the base rather than from above. Watering from above can cause the leaves to stay wet for extended periods, creating an ideal environment for the fungus to grow.
- Avoid overcrowding your plants. Overcrowded plants are more susceptible to powdery mildew because the leaves don’t have enough space to dry off quickly after watering.
- Prune your tomato plants regularly to remove any dense, unnecessary foliage. This will improve the airflow around your plants and further protect them from disease. Only use sanitized trimmers, knives, and garden tools to prune your plants to avoid spreading diseases among them.
- Remove any affected leaves from your plant as soon as you notice them. This will help prevent the fungus from spreading.
- Dispose of diseased tomato leaves and stems – don’t compost them. Burning them is also an option if you have a safe place to do so.
What should you do if your plants get afflicted with powdery mildew?
If you notice powdery mildew on your tomato plants, there are a few things you can do to treat it:
- Try using a fungicide specifically designed for powdery mildew. These can be found at most garden stores or online.
- Use a popular homemade remedy for powdery mildew. Mix one part of the milk with nine parts of water and spray it on the affected leaves. The milk will help kill the fungus and prevent it from spreading further. You’ll need to reapply this treatment every few days until the fungus is gone.
- Practice good hygiene in your garden. This means keeping your tools clean and disinfected and washing your hands after working in the garden.
What is sunscald?
Sunscald occurs when the fruit of a plant is exposed to too much direct sunlight. The hot sun can cause the fruit to ripen too quickly, resulting in patches of white or yellow discoloration. Sunscald is most common in late summer or early fall when the weather is hot and sunny.
How to prevent sunscald?
The best way to prevent sunscald is to provide some type of shade for your plants that are in direct sun for much of the day. This can be done by planting them in an area with partial sun, using a shading cloth, or building a simple frame around the plants.
What to do if your tomato plants have sunscald?
If you notice sunscald on your plants, you can do a few things to help mitigate the damage:
- Try to provide some type of shade as soon as possible. Shade cloth is a popular and effective method for shading tomato plants and other garden fruits and vegetables.
- Remove any affected fruit from the plant.
- Water your plants regularly and consistently; stressed plants are more susceptible to sunscald.
4. Misc. reasons for white spots on tomato leaves
Weather issues during transplanting
Growing young tomato seedlings indoors is common for extra care and protection from unpredictable climate conditions. You can also enjoy an extended gardening season by planting tomatoes indoors.
When temperatures average 55 to 60° F overnight, you can start planting them outdoors. A common mistake gardeners make when caring for young tomato seedlings is that they immediately transplant them outside without any acclimation.
You need to properly harden off your tomato seedlings before planting them outdoors. Tomato seedlings must be transplanted slowly and gradually from indoors to outdoors to learn how to survive in harsher conditions.
If the young tomato seedlings aren’t gradually transitioned, they can enter into a state of shock due to their heightened vulnerability to light, heat, and wind.
All that stress can cause the plant to experience sun scalding. A white border will appear around the leaves of the tomato plant if it’s affected by sun scalding. Scalding quickly damages all the foliage on young tomato plants.
High humidity levels
Tomato plants need the perfect amount of humidity to grow and prosper. If there’s too little or too much of it, the plant will not develop into a healthy, mature one.
Infection is more likely to occur with insufficient sunlight and conditions that maintain high humidity levels (above 70%). Common fungal infections like powdery mildew often happen due to high humidity levels. Powdery mildew damages the plant’s fruit and creates white spots on the tomato leaves.
A plant can have too much water, just like it could have too little. Watering your tomato plant should be done at a controlled and sufficient amount; otherwise, the high concentration of water in the soil could create an environment where fungal spores prosper.
Many fungal infections are caused by too much water. Not just powdery mildew but also root rot, Alternaria, and Septoria leaf spots.
Become familiar with how much water your tomato plants need, which will vary depending on your local climate conditions. In some places, watering tomato plants deeply one time per week is enough. In drier areas, tomatoes need water every day or every other day.
Familiarity with how much water each of your plants’ needs comes with time and experience. As you gain experience as a gardener, you’ll start to sync up with your plants’ water needs, so don’t feel bad if it all seems like a struggle initially. Just keep at it, stay observant, and treat your garden as a teacher – you’ll soon feel much more confident about knowing how much water your plants need.
Extreme wind conditions
Though high winds do not turn tomato plant leaves white, they can quicken the infection rate spread from one part of the plant to another.
If you spot a section of your tomato plant with white spots from infection, you’ll need to address it with the methods discussed in this article. Wind can intensify disease symptoms when these conditions are present, so these areas should be handled with first priority.
All living things need essential nutrients to grow and develop properly. Nutrient deficiency should be paid close attention to when caring for young seedlings as they mature into plants. The lack of specific nutrients can cause tomato plants to turn white.
For example, a lack of nutrients such as nitrogen and phosphorus may cause white or yellow spots on tomato plants. Also, low levels of calcium and magnesium might white the leaves while still keeping the veins green.
FAQs about white spots on tomato leaves
How do you fix tomato leaf spots?
There are a few possible causes of white spots on tomato leaves, including powdery mildew, sun scald, and late blight. Try to identify the cause so you can take appropriate action to treat it.
How do you get rid of white spots on plants?
If the white spots are caused by powdery mildew, you can try treating it with a homemade fungicide made from milk and water. For other causes, such as sun scald or late blight, you’ll need to take different actions to treat the problem.
How do you stop white spots on tomatoes?
The best way to stop white spots on tomatoes is to prevent them from happening in the first place. This can be done by planting disease-resistant varieties, using soaker hoses for irrigation, and keeping the area around your plants clear of debris.
How do you treat white leaves on tomato plants?
The best way to treat white leaves on tomato plants is to figure out the cause of the problem and take appropriate action. Possible causes include powdery mildew, sun scald, and late blight. Once you know the cause, you can take steps to treat it accordingly.
Powdery mildew can be treated with a homemade fungicide made from milk and water. Sun scald can be prevented by using mulch or row covers. And late blight can be treated with a fungicide specifically designed for that purpose.
How do you fight tomato fungus?
There are a few different types of tomato fungus, including powdery mildew, Alternaria, and Septoria leaf spot. Airflow is important for preventing all kinds of fungal infections in tomato plants. Plant your tomatoes with 12-18 inches of space between them and keep them well-pruned to increase airflow.
Powdery mildew can be treated with a homemade fungicide made from milk and water. Alternaria can be prevented by using row covers. And Septoria leaf spot can be treated with a fungicide specifically designed for that purpose.
How can I prevent powdery mildew from occurring in my garden?
You can prevent powdery mildew by watering your plants at the base rather than from above. Watering from above can cause the leaves to stay wet for extended periods, creating an ideal environment for the fungus to grow. Avoid overcrowding your plants and remove any affected leaves from your plant as soon as you notice them.
Can sun scald be prevented?
The best way to prevent sun scald is to provide some type of shade for your plants that are in direct sun for much of the day. This can be done by planting them in an area with partial sun, using a shading cloth, or building a simple frame around the plants.
What are some common tomato plant diseases?
Some common tomato plant diseases include powdery mildew, late blight, mosaic virus, and Verticillium wilt. Tomato plants can also be susceptible to sun scald, blossom end rot, and catfacing.
White spots on tomato leaves can be caused by a lack of specific nutrients, sun scald, or late blight. The best way to prevent them is to identify the cause and take appropriate action. One of the best ways to avoid white spots on tomato leaves is to increase your experience with gardening because you’ll be able to diagnose tomato issues quickly.