As the heat of summer approaches, many vegetable gardeners face a familiar problem – tomato sunscald. This phenomenon, caused by too much sunlight and made worse by improper pruning practices, can pose a significant threat to your tomato yields.
Tomato plants love sunlight, but sometimes it can be a case of “too much of a good thing.” They like 6-8 hours of sunlight a day and can withstand a few days of higher than normal temperatures without too much problem.
However, if this continues for days on end, sunscald can rear its ugly head.
Let’s find out how to recognize sunscald and learn how to prevent it so that your tomato plants are healthier, and you end up with a better harvest.
What is sunscald?
Sunscald is not a disease, but a disorder that impacts plants. It is caused by exposure to excessive sunlight. Think of it as a plant’s version of sunburn.
Tomatoes often experience this problem, but other vegetables can suffer, as well, particularly those with delicate skins or exposed fruits. Vegetables affected most often are:
- the nightshade family – tomatoes, peppers and eggplant
- the cucurbit family – cucumbers, melons, summer squash and winter squash
Sunscald in tomatoes can happen all over the country, but it is more often a problem in the South where the days are longer and hotter. It will often happen during the ripening stage.
Symptoms of tomato sunscald include light blotchy patches, yellowing, and eventual decay. Left untreated, the tomatoes may crack or end up with paper-like skin and sunken areas on the flesh.
If the fruit continues to deteriorate, it can be a breeding ground for other problems. Common diseases such as bacterial spot, bacterial wilt, early blight, and powdery mildew can take hold when a plant’s natural defenses are compromised.
Can you eat sunscald tomatoes?
Yes, you can still eat tomatoes affected by sunscald, but it’s essential to inspect them carefully. Sunscald typically affects the skin of the tomato.
While these areas may not look appealing, the rest of the tomato is usually unaffected and safe to eat. Simply cut away the damaged portions, and the remaining flesh should be perfectly fine for consumption.
However, if the sunscald has progressed to the point of significant decay or mold, it’s best to discard the tomato to avoid any risk of illness.
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Causes of sunscald in tomatoes
Sunscald stems primarily from too much sunlight. However, several factors can make the disorder worse.
Let’s explore the various causes of sunscald and look at some practical ways to lessen its effects on your tomato plants.
Overexposure to strong sunlight
Intense sunlight can directly damage plant tissues, leading to sunscald. While we can’t stop Mother Nature from doing her thing when it comes to sunlight, there are a few things we can do to make the strength of it less harsh.
Provide adequate shading, especially during peak sunlight hours. This can help to protect plants from excessive sun exposure.
Use lightweight shade cloth or provide natural shading from taller plants to create a protective environment.+
High temperatures can cause sunscald
High temperatures make sunscald worse by intensifying the effects of sunlight and increasing water loss from the plant. It is also a common reason why tomatoes won’t turn red on the vine.
Ensure that your plants receive sufficient water to help regulate their temperature and reduce heat stress. Mulching around plants can also help retain soil moisture and moderate soil temperature.
Consider using drip irrigation or soaker hoses to deliver water directly to the roots rather than from above.
Too thin a plant cover
Sparse foliage exposes plants to direct sunlight, increasing the risk of sunscald.
If you have been pruning your tomato plants and have removed too much foliage, you may have unwittingly caused sunscald.
Insufficient foliage means less shade and less protection for fruits and other exposed plant parts, leaving them vulnerable to direct sunlight.
Encourage dense foliage growth by avoiding over-pruning and providing appropriate spacing between plants. Planting companion plants or using trellises can also help create natural shading for vulnerable plants.
If you need to prune your tomato plants, focus on removing only dead or diseased branches. Take care to leave the healthy foliage to provide natural shade for fruits and other plant parts.
Reflective surfaces can worsen tomato sunscald
Surfaces such as white walls, rocks, or even reflective mulch can intensify sunlight and increase the risk of sunscald by redirecting and focusing sunlight onto plants.
Minimize the use of reflective surfaces near plants by using light-colored mulches or positioning reflective objects away from plantings. Installing shade structures or using barriers to diffuse sunlight can also help reduce its intensity.
Choose tomato varieties resistant to sunscald
Some tomato varieties may be more susceptible to sunscald due to factors such as thin skin or light-colored fruits. Large indeterminate types with sprawling fruit surface may be more challenging to manage in terms of sunscald prevention.
Older heirloom varieties may lack the disease resistance and sunscald tolerance found in newer hybrid varieties. Long-ripening types may spend more time exposed to sunlight, increasing their susceptibility to sunscald.
When shopping for seeds, choose those known for their tolerance to sunscald or those with thicker skin and darker-colored fruits.
Some tomato varieties known for their relatively higher resistance to sunscald:
- Sun Gold – This cherry tomato variety is prized for its exceptional sweetness and resistance to cracking and sunscald. Its small size and rapid ripening make it less susceptible to sun damage.
- Jet Star – Jet Star tomatoes are known for their smooth, crack-resistant skin and excellent flavor. They tend to have denser foliage, which can provide some protection against sunscald.
- Heatwave II – Bred specifically for hot climates, Heatwave II tomatoes exhibit tolerance to heat stress and sunscald. They produce medium-sized, flavorful fruits.
- Prairie Fire – Suited to Florida temperatures. This determinate variety produces early and its small size offers some protection compared to larger varieties.
- Mountain Fresh Plus – Well-suited for hot, humid climates, Mountain Fresh Plus tomatoes exhibit resistance to sunscald, cracking, and various diseases. They produce large, flavorful fruits.
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Printable - Tomato Varieties Resistant to Sunscald
Have you noticed that your tomato plants are developing yellow areas instead of ripening to a red color? You may be experiencing tomato sunscald.
While no varieties are completely resistant to this tomato plant problem, some are more unlikely to encounter it.
Print out this shopping list and add it to your garden journal for reference when you go shopping for tomato seeds.
Materials
- Heavy card stock or printer paper
Tools
- Computer printer
Instructions
- Load your printer with heavy card stock or printer paper.
- Choose portrait layout and if possible "fit to page" in your settings.
- Take the shopping list with you the next time you go plant shopping for tomato seeds.
Notes