What’s Wrong with My Tomato?
Ah, summer. How we love your lazy, hazy days. But let’s be honest: we love summer most for those garden-fresh, scrumptious tomatoes that we’ve missed all winter. BLTs. Bruschetta. Kabobs. Caprese salad. Really, is there any homegrown goodie more beloved than tomatoes?
But what happens when our anxiously-awaited fruit disappoints with low yield, funky leaves, weird black splotches, or—gasp!—pre-nibbled orbs? Even the most vigilant gardener may suffer angst over tomato problems.
But no worries, friends. We’re here to help!
We’ve identified the top 10 tomato problems—and how to solve them—so you can savor the delicious flavor of your carefully-cultivated, eagerly-awaited, homegrown treats.
Common Disease Abbreviations Key
If you come across disease abbreviations, this key can help you decipher their meaning. It’s common for diseases and resistant varieties to be labeled with abbreviations only.
Problem #1: Blossom-End Rot (BER)
What Is Blossom End Rot?
A nasty-looking, black, bruise-like, water-soaked area, typically on the blossom end (the side opposite the stem) of the tomato. The area grows and becomes sunken and leathery. In some cases, the exterior of the fruit looks fine, but the inner fruit is discolored. It often appears on the first fruits of the season. BER also affects peppers, eggplant, and squash.
Causes of Blossom End Rot:
Lack of calcium in the fruit. Many gardeners think that it’s a lack of calcium in the soil that causes BER—which can be a factor. However, this physiological disorder results from a lack of calcium in the fruit.
Often, there’s adequate calcium in the soil, but the plant’s ability for calcium uptake and transport to the fruit is impaired. Drought stress and inconsistent watering cause root hair damage. Waterlogged soil, cold soil, high concentrations of ammonium, potassium, and magnesium in the soil…all of these factors can lead to blossom-end rot.
Solutions for Blossom End Rot:
- Always test your soil before amending it to determine if it needs more calcium. If a soil test shows low calcium levels, add garden lime, bonemeal, or finely-crushed eggshells (the smaller the particles, the better) to the soil. If it does not show low calcium levels, don’t add any!
- Check the soil pH. Most vegetables and fruit, including tomatoes, prefer a pH around 6.5.
- Avoid planting tomatoes too early, as cold, wet soil can damage roots and root hairs, leading to BER.
- Do not over-fertilize. Tomatoes are heavy feeders, but follow instructions on fertilizer labels, and avoid too much nitrogen.
- Irrigate plants evenly. Tomatoes like consistently moist—not soggy—soil.
- Select tomato varieties resistant to BER, like Mountain Rouge and Early Resilience.
Problem #2: Blossom Drop
What Is Blossom Drop?
Flower stems turn yellow, and flowers dry up and fall off—leaving a fruitless tomato plant. Blossom drop also affects peppers.
Causes of Blossom Drop:
Blossom drop typically occurs during extreme temperatures: when it’s either too hot or too cold.
Tomatoes prefer daytime temperatures between 70 to 85 degrees Fahrenheit. When summer temps soar over 90 degrees for several days in a row, and nighttime temps remain above 72 degrees, the pollen of self-fertile tomato plants can become non-viable. If pollination doesn’t occur within several days of bloom, the flowers dry up and fall off.
When nighttime temperatures fall below 55 degrees, the cold temperatures stress the plant, which can also lead to blossom drop.
Humidity that’s too high may make the pollen too sticky, or humidity that’s too low may make it too dry, with both extremes leading to a lack of pollination.
Too much nitrogen in the soil increases vegetative growth—but reduces flower formation.
Solutions for Blossom Drop:
- Wait to plant tomatoes until nighttime temperatures are consistently above 55 degrees Fahrenheit.
- Test the soil before adding amendments.
- In hot climates, plant tomatoes where they receive a bit of afternoon shade.
- During heatwaves, cover plants with a 30% shade cloth.
- Water consistently, using drip irrigation.
- Select a fertilizer ideal for tomatoes. Avoid excess nitrogen.
- Choose early-maturing varieties for extremely hot areas, like Red Torch and Sparky XSL.
Problem #3: Cracked Fruit
What Is Cracked Fruit?
Concentric cracks that appear in a circle around the stem-end of the tomato, as well as radial cracks that form perpendicular to the tomato stem. Primarily affecting the fruit cosmetically, diseases can also develop in areas with open cracks.
Causes of Cracked Fruit:
While uneven moisture is the prime culprit for causing cracks in tomatoes—especially during times of rapid fruit growth—many tomato varieties are simply genetically prone to cracking.
Solutions for Stopping Cracked Fruits:
- Water plants consistently.
- Mulch tomato plants to maintain even soil moisture.
- Reduce watering as tomatoes near ripeness.
- Pick nearly-ripe tomatoes early if heavy rain is forecasted, allowing the fruit to finish ripening indoors.
- Select varieties bred for crack resistance, like Buffalosun, Sunset Torch, and Chef’s Choice Orange.
Problem #4: Sunscald
What Is Sunscald?
White or yellow blisters develop on the side of the tomato facing the sun. Sunscald occurs most often on green fruit. The area may become papery, grayish-white, and flattened. Black mold can grow on the damaged area, causing fruit to rot.
Causes of Sunscald:
Much like gardeners exposed to too much sun, tomatoes can also suffer sunburns. Sunscald occurs when the fruit is exposed directly to the sun, especially in hot weather. Over-pruned plants or lost foliage due to disease exposes fruit to the strong sun rays, blistering the fruit’s skin and wall of the tomato.
Solutions for Sunscald:
- Maintain healthy plants and foliage.
- Water plants regularly and consistently with drip irrigation. Avoid splashing water on leaves, which can lead to foliar disease.
- Mulch plants to maintain soil moisture and to avoid soil splashing on leaves when watering, which can lead to disease.
- Practice crop rotation and good sanitation to avoid foliar diseases.
- Apply fungicides, if needed.
- Cover exposed fruit with a shade cloth.
Prevention is always the best remedy.
Make sure to clean up fallen fruit, remove diseased tomato leaves, and practice good garden hygiene to avoid soil-borne diseases. Disinfect tools and supports to prevent the spread of diseases between plants.
Problem #5: Poor Fruit Set
What Is Poor Fruit Set?
Plants produce few to no tomatoes, breaking the gardener’s heart. Poor fruit set most often occurs on large-fruited heirloom varieties.
Causes of Poor Fruit Set:
Lack of fruit can result from blossom drop. Daytime temperatures above 90 degrees Fahrenheit and nighttime temps above 70 degrees hinder pollination, resulting in poor fruit set. Very high or very low humidity levels can also cause poor fruit set. Too much nitrogen in the soil can lead to excessive foliage and low flower production.
Solutions for Poor Fruit Set:
- Follow the recommendations to resolve blossom drop (above.)
- Stagger the planting of tomatoes to increase the odds of successful fruit sets throughout the season.
- Test the soil to rule out excessive nitrogen.
- Apply tomato-specific fertilizer, according to the directions on the label.
- Select varieties bred for high fruit production, like Juliet and Celano.
Problem #6: Cat-Facing
What Is Catfacing?
Brown creases and folds that form on the blossom end of the tomato create an unattractive—but still edible–fruit. The blossom scar becomes enlarged or perforated, and the fruit may become misshapen. Typically affects larger fruit, like beefsteak tomatoes. This is not the tomato you want to show off on your Instagram feed.
Causes of Catfacing:
Environmental conditions like long periods of cool daytime temperatures (60 to 65 degrees) and nighttime temperatures (50 to 60 degrees) can cause abnormal development of plant tissue between the style and ovary. Damage from thrips to the side of the pistil may also result in cat-facing. Soil that’s overly rich in nitrogen can also lead to cat-facing, as well as overly aggressive pruning of the plant.
Solutions for catfacing:
- Plant when the temperatures warm to avoid damage to flowers.
- Avoid excessive pruning.
- Test soil for excessive nitrogen and amend the soil as recommended.
- Plant smaller tomato varieties, or select newer varieties bred for “smooth” appearance, like Mountain Merit and Galahad
For the healthiest tomato plants, practice crop rotation.
Don’t plant tomatoes in the same bed each year, because diseases can linger in the soil.
Problem #7: Yellow, Spotty, Wilted Foliage
What Is Yellow, Spotty, Wilted Foliage on Tomatoes?
Lower leaves turn yellow, or the plant experiences an overall yellowing/wilting of foliage, which can lead to foliage drop.
Causes of Yellow, Spotty, Wilted Foliage on Tomatoes:
Sometimes, despite your best care, you’ll notice tomato leaves turning yellow, ugly brown spots popping up, or foliage wilting. It’s frustrating because you can’t see the culprits behind these attacks: they may be fungal, bacterial, or viral infections.
Early blight (Alternaria fungus), leaf spot (septoria fungus), bacterial canker, bacterial pith necrosis, or verticillium or fusarium wilt are some of the nasty nemeses that may be wreaking havoc in your garden.
Solutions for Yellow, Spotty, Wilted Foliage on Tomatoes:
- Remove and destroy yellow foliage if it’s just primarily on the lower leaves.
- If the yellowing spreads upwards quickly and is accompanied by wilting, remove the entire plant to prevent the disease from spreading.
- Do not compost affected foliage or plant.
- Mulch around the plant to prevent soil from splashing onto the leaves.
- Rotate crops to avoid planting tomatoes in affected soil.
- Disinfect/wash containers and tomato supports to prevent the spread of diseases.
- Select disease-resistant tomato varieties. Look for varieties with multiple disease resistances, such as “Resistant to fusarium wilt (F), verticillium wilt (V), tobacco mosaic virus (TMV), nematodes (N), late blight (LB), and anthracnose (A).” Try Big Beef, Celebrity, Pink Delicious, and Early Resilience F1.
Do you know that today’s innovative breeders are creating products that are healthier and less disease prone?
You’ll find the latest, greatest tomato varieties in the AAS Winner line-up.
Problem #8: Dark Spots on Fruit
What Are Dark Spots on Tomatoes?
Ripe fruit develops ugly, sunken, black, or brown spots.
Causes of Dark Spots on Tomatoes:
A nasty pathogen, anthracnose lurks in soil, with its spores splashing onto the plants. Infection is more likely when it’s warm, with temperatures over 80 degrees. Initially, small, circular, depressed areas form on the fruit, which grows larger over time and become darker as the fungus produces spore-containing structures. While more evident on ripe fruit, it can also infect green fruit, with the symptoms developing as the fruit begins to ripen.
Solutions of Dark Spots on Tomatoes:
- Trellis tomatoes to reduce the likelihood of soil splashing on plants when watering.
- Use drip irrigation, and make sure the soil drains well.
- Mulch around plants to reduce soil splashing on leaves.
- Remove infected fruit immediately—don’t let it fall on the ground.
- Rotate areas where tomatoes are grown to prevent spread from previous crop.
- Do not grow any solanaceous (tomatoes, peppers, eggplants) plants in the affected area for 3 years.
- Don’t save seeds from affected plant, as the pathogen is also seed-borne.
- Apply fungicides to prevent the spread to other plants.
- Select tomato varieties that resist disease, such as Chef’s Choice Orange and Purple Zebra.
Problem #9: Leaf Roll
What Is Leaf Roll on Tomatoes?
Tomato leaves curl either up or down, instead of presenting normally.
3 Causes of Leaf Roll on Tomatoes:
Tomato leaf roll is tricky to diagnose because many factors can cause it.
1. Physiological leaf roll occurs due to cultural or environmental factors, such as excess moisture, too much nitrogen in the soil, insufficient phosphorus, heat, drought, severe pruning, root damage, early planting, and transplant shock. Initial symptoms present on lower leaves, with upward cupping of leaflets, followed by an inward lengthwise rolling toward the mid-vein. Leaves tend to thicken into a leathery texture, but they retain a healthy green color. Over time, all leaves may be affected, but generally, physiological leaf roll has little impact on fruit production.
2. Viral infections are not so kind to your tomato plants.
- Tomato yellow leaf virus, which is transmitted by whiteflies, causes new leaves to become cupped and pale green. The entire plant may exhibit stunted growth, yellowing leaf edges, purplish veins on the undersides of leaves, and a decline in fruit production.
- Tomato mosaic virus also causes leaf rolling, along with the mottled coloring of leaves, small leaflets, and internal browning of infected fruit.
3. Herbicide damage can also cause leaf rolling, but with the leaves rolling downward. It may also cause twisted growth, stems may turn white and split, the fruit may be deformed, and the plant may perish. However, new growth may be normal.
Solutions for Leaf Roll on Tomatoes:
Determine the cause of the leaf roll: physiological, viral, or herbicide.
- Physiological leaf roll: test soil for excessive nitrogen, and amend the soil as recommended based on the test; make sure soil drains well; water consistently with drip irrigation; avoid severe pruning; plant when temperatures are consistently warm; avoid damaging roots; harden off seedlings before planting in the garden.
- Viral leaf roll: remove surrounding weeds, which may host insects that transmit viral diseases; remove and dispose of infected plants, as there’s no cure for tomato yellow leaf curl or tomato mosaic viruses; do not compost infected plants; disinfect tools and plant supports; practice crop rotation; select disease-resistant tomato varieties like Crokini and Fire Fly
- Herbicide damage cannot be reversed, and the plant may ultimately die. However, if minimal exposure, the tomato plant’s new growth may be normal. Remove dead portions of the plant. Protect future plants when spraying herbicides.
Problem #10: Nibbled Fruit
What Is Nibbled Fruit?
Someone—not you—sampled the tomatoes in the garden.
Causes of Nibbled Tomatoes:
Deer, birds, tomato hornworms, tomato fruit worms, slugs, snails, raccoons, opossums…so many culprits.
Solutions to Nibbled Tomatoes:
- Check plants daily for eggs and pests, then remove them.
- Attract beneficial insects to the garden with companion plants.
- Employ Integrated Pest Management methods to encourage predatory insects, like parasitic wasps, to visit the garden. Parasitic wasps use tomato hornworms as hosts for their eggs, effectively killing them as the larva hatches.
- Erect tall fencing (7 feet or more) around the garden to discourage deer.
- Use motion-activated sprinklers to discourage mammals and birds.
- Apply repellent sprays to discourage mammals.
Armed with a cheat sheet to identify tomato problems—and how to solve them—you’ll soon enjoy delicious days filled with scrumptious summer tomatoes.
Bon Appetit!
AAS Winners
Leave a Comment