Black Spots On Tomatoes

If you’ve ever grown tomatoes, you’ve probably seen those frustrating dark marks. Understanding and preventing black spots on tomatoes is key to a healthy harvest. These spots can come from several issues, but the good news is that most are preventable. This guide will help you identify the common culprits and give you clear steps to protect your plants.

Those black spots aren’t just one problem. They are a symptom. The cause could be a disease, a pest, or an environmental issue. Correct identification is your first and most important step. Treating a fungal disease when the problem is actually sunscald won’t help your plants. Let’s look at the most common causes.

Common Causes of Black Spots

Here are the usual suspects for black or dark spots on your tomato fruits and leaves.

Blossom End Rot: This causes a leathery, sunken black or brown spot on the bottom (blossom end) of the fruit. It’s not a disease but a calcium issue often linked to uneven watering.
Early Blight & Septoria Leaf Spot: These fungal diseases start as small dark spots on lower leaves, often with yellow halos. They can spread to stems and, in severe cases, affect the fruit.
Bacterial Spot & Speck: These cause small, raised black spots or specks on green fruit, leaves, and stems. They are spread by splashing water and thrive in warm, wet weather.
Sunscald: This appears as a white or pale yellow patch that turns papery and may develop black mold. It happens when fruit is overexposed to direct, hot sun, often after leaf loss.
Catfacing: This is a misshapen fruit with scars and blackened crevices. It’s caused by cool temperatures during flowering and is more common in heirloom varieties.

How to Diagnose Your Tomato Problem

Look closely at where the spot is and what it looks like. Ask yourself these questions:

Is the spot on the bottom of the fruit? It’s likely Blossom End Rot.
Are there small spots on the leaves first? Think fungal or bacterial disease.
Is the spot on the top or side of the fruit, facing the sun? Consider sunscald.
Is the fruit also twisted or scarred? It could be catfacing.

Once you know the cause, you can take action. Prevention is always easier than cure, so lets focus on that.

Preventing Blossom End Rot

Blossom end rot is heartbreaking but fixable. Since it’s a calcium uptake problem, not a soil deficiency, consistent care is the solution.

Water Evenly: This is the number one rule. Tomatoes need 1-2 inches of water per week. Use a soaker hose or drip irrigation to water deeply at the soil level, not the leaves. Mulch heavily to retain moisture.
Test Your Soil: A soil test can confirm pH is between 6.5 and 6.8, which is ideal for calcium uptake. If pH is too low, add garden lime.
Avoid Excessive Nitrogen: High-nitrogen fertilizers promote leafy growth at the expense of fruit and can hinder calcium absorption. Use a balanced fertilizer or one formulated for tomatoes.

If you see affected fruit, remove it so the plant can put energy into healthy new fruit.

Stopping Fungal and Bacterial Diseases

Fungi and bacteria love moisture. Your goal is to keep leaves as dry as possible and improve air flow.

Smart Gardening Practices

Rotate Crops: Never plant tomatoes in the same spot two years in a row. A 3-4 year rotation is best to break disease cycles.
Choose Resistant Varieties: Look for labels with “VFN” or “EB” resistance. This means the plant has bred-in resistance to common wilts and blights.
Space Plants Properly: Give plants plenty of room. Crowded plants stay wet and spread disease quickly. Follow spacing on the plant tag.
Water at the Base: Always water the soil, not the plant. Soaker hoses are perfect for this.
Mulch: A layer of straw or wood chips prevents soil-borne spores from splashing up onto leaves during rain or watering.
Prune for Airflow: Remove the lower 12 inches of leaves to prevent contact with soil. Prune suckers to keep the plant open.
Clean Up: In fall, remove all tomato debris from the garden. Do not compost diseased plants; throw them away.

Using Preventative Sprays

For added protection, especially in humid climates, consider organic sprays.

Copper Fungicide: Effective against both fungal and bacterial diseases. Apply preventatively when conditions are favorable for disease.
Baking Soda Spray: Mix 1 tablespoon baking soda, 1 teaspoon horticultural oil, and 1 gallon of water. Spray weekly to create a surface unfriendly to fungi.
Chamomile or Compost Tea: These can have mild antifungal properties and boost plant health overall.

Avoiding Sunscald and Catfacing

These problems are related to environment and weather.

For sunscald, the key is to maintain healthy leaf cover to shade the fruit. Avoid over-pruning. If a plant has lost many leaves to disease, you can provide temporary shade with a lightweight cloth. Choosing varieties with good foliage cover helps too.

Catfacing is trickier to prevent because it’s caused by cool nights (below 58°F) during flowering. You can protect early plants with row covers or cloches to keep them warmer. Planting a bit later, when nights are consistently warmer, can also help. Some varieties are just more prone to it than others.

Your Seasonal Prevention Plan

Before Planting (Spring)

Test your soil and amend for proper pH.
Choose disease-resistant tomato varieties suited to your area.
Plan your garden layout with proper crop rotation.

At Planting Time

Space plants correctly.
Install stakes or cages right away to avoid damaging roots later.
Set up your soaker hose or drip irrigation system.

During the Growing Season

Water deeply and consistently, aiming for the soil.
Apply a thick layer of mulch after the soil has warmed.
Prune lower leaves and some suckers for airflow.
Apply organic preventative sprays if needed, especially after rainy periods.
Fertilize with a balanced, tomato-appropriate fertilizer according to package directions.

At Season’s End (Fall)

Remove all tomato plant debris from the garden.
Clean your stakes and cages with a bleach solution.
Add compost to the bed to improve soil structure for next year.

What to Do If You See Black Spots

Don’t panic. Act quickly to save the rest of your crop.

Identify: Use the guide above to figure out the most likely cause.
Remove Damage: Pick off and discard badly affected leaves or fruit. For diseases, put them in the trash, not your compost.
Adjust Care: Improve your watering, apply mulch, or prune for better air flow immediately.
Treat: Apply an appropriate organic treatment, like copper fungicide for spreading diseases.
Monitor: Keep a close eye on the plant to see if the problem stops spreading.

Remember, a few spots don’t mean the whole plant is lost. Often, you can still harvest plenty of healthy tomatoes from a plant with some issues.

FAQ: Black Spots on Tomatoes

Can you eat tomatoes with black spots?

It depends on the cause. You can cut away small areas affected by sunscald or blossom end rot and eat the rest of the fruit. Do not eat fruit with obvious fungal growth or rot. If in doubt, throw it out.

What is the best fungicide for tomato black spots?

For organic gardens, copper fungicide is a broad-spectrum option for both fungal and bacterial issues. Chlorothalonil is a common synthetic option. Always read the label and apply preventatively for best results.

Does overwatering cause black spots?

Indirectly, yes. Overwatering or uneven watering leads to blossom end rot. It also creates the wet conditions that fungal and bacterial diseases need to thrive. Consistent, deep watering is much better than frequent light sprinklings.

Why are there black spots on my tomato leaves?

Black spots on leaves are almost always a sign of fungal disease like early blight or Septoria leaf spot. Bacterial diseases can also cause them. Remove affected leaves, improve air circulation, and avoid wetting the foliage when you water.

Growing tomatoes is incredibly rewarding, and a few challenges shouldn’t deter you. By focusing on soil health, consistent watering, and good garden hygiene, you can prevent most causes of black spots. Start with strong, resistant varieties and give them the care they need. Your efforts will be rewarded with a bountiful and beautiful harvest of healthy, homegrown tomatoes all season long.