Of the many tomato problems that can occur, white leaves is among the most common. There are a few possible causes, depending on the appearance of the leaves.
In this article, I’ll discuss tomato leaves turning white, common causes, and how to solve the issue going forward.
To give a quick answer, tomato leaves often turn white when they are under sun stress, and the solution is to properly harden the plants before transplanting.
Sun Scald
The first, and most likely culprit for your tomato leaves turning white is sun scald. This is basically a sun burn on your tomato plants, and it is incredibly common.
It goes like this: you buy a tomato plant from a local nursery, bring it home and put it into the garden. A few sunny days pass, and BAM – your tomato leaves start to turn white, shrivel up, become crunchy, and often fall off.
Symptoms:
- Entire leaf turning white
- Dried up, hardened leaves
- Brittle and eventually crunchy
- Leaves fall off
This is due to improper hardening off for your tomato plants. The younger plants often have delicate, thin foliage that is very susceptible to the powerful mid-day sunshine.
To help resolve the issue, try to provide some shade during the middle of the day. You can use floating row cover, an umbrella, or simply move your potted tomato plants into the shade for a few hours around noon.
How To Harden Off Tomato Plants
I wrote an entire article about hardening off tomatoes here. This process is critical, especially if you are growing your own plants from seed. Indoor plants need time to acclimate to wind, rain, and especially sunshine.
The process is fairly simple. Your goal is to gradually increase the amount of direct sunlight that your plants receive. This is accomplished through increasing outdoors time daily, bringing the plants indoors at night.
You can begin hardening about 2 weeks before your tomatoes go outside permanently. Start on a cloudy day, or start with your plants in full shade. After 2-3 days of shade, they will be ready for a brief time in the sun, around 30 minutes.
Increase the daily sun exposure by about 15-30 minutes per day for another 10 days or or so until the plants can handle full sun. If your plants show signs of stress, like wilting leaves or white spots, then bring them back into the shade to cool down.
Tiny White Spots on Tomato Leaves
Tiny white spots can indicate a few possible issuse with your tomato leaves. If the spots appear to be fuzzy or powdery, skip ahead to powdery mildew. Otherwise, consider these possible causes for the white tomato leaves.
Pest Damage
There are countless insects that would love to make a feast out of your tomato plants. From mites to aphids to caterpillars and more – you’ll have to be on the lookout for these pesky garden enemies!
White spots on tomato leaves may indicate some sort of infestation. If you have ruled out sunscald as a possible cause, check for insects. You’ll have to look closely, as many of the more sneaky bugs are hard to see.
Tips to find pests:
- Look underneath leaves
- Look at newer foliage (younger leaves)
- Use a magnifier
- Look against the light and look for small shadows
Aphids can be a real nuisance for tomato growers. They are incredibly common and there are around 5,000 different species known! These sap-sucking pests generally feed underneath leaves.
The best way to deal with pests is to catch them before they turn into an infestation. Aphids and other pests multiply rapidly, so catching and getting rid of them early in the Spring is key.
Use a hose to spray off aphids early in the season and plant decoy plants nearby your tomatoes. These are plants that are more attractive to aphids, effectively giving them something else to snack on.
If the problem persists, I like to use a neem oil spray with a few drops of castile soap to soak the leaves, top and bottom. This is an all-natural insecticide that can take care of many types of bugs, but may also harm some beneficial insects.
Manganese or Other Nutrient Deficiency
If there are no insects, you may have a specific nutrient deficiency. If you have not been feeding an all-purpose fertilizer, this is very possibly your culprit. Tomatoes require a good balance of plant nutrients to remain healthy all year long.
A lack of manganese can cause spots on leaves, often gray or white in color. The solution is simple – begin feeding a general purpose fertilizer, and allow the plant to recover over the course of a week. If new growth improves, you know what the issue was!
Diseases
In addition to pests, disease and viruses are potential threats to a tomato plant. Aphids often act as a vector for bringing disease to your tomatoes, so dealing with pests should be a priority.
However, I always take several precautions every year to help reduce the chances of infection. Things like bottom pruning, proper plant spacing, and plant mulching all help reduce disease.
Powdery Mildew
One of the diseases that causes white spots on tomato leaves is powdery mildew. This is more common to have on squash (and other gourd-type plants), but it does infect tomatoes as well.
Powdery mildew is a fungal disease that is common and can be transmitted via woolly aphids. The disease presents in white, powdery patches on leaves, spreading throughout the plants quickly.
To stop powdery mildew, start by carefully removing and disposing of any affected areas of the plant. Then, you may need to resort to some type of chemical control. Learn more here.
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I hope this article helps you identify why your tomato leaves are turning white. There are several possibilities, but the most common are almost always to blame.
To summarize, sun scald is most likely, and is caused by sudden exposure to intense sunlight. Pest damage or nutrient deficiency can display as white or yellowing dots on leaves. Finally, some diseases can present themselves as white spots or patches on tomato leaves.
Let me know how your plants are doing after dealing with the white leaves – I always love to see a tomato plant recover from having issues!