Early Blight on Tomatoes: Best Treatment for Alternaria Leaf Spot

Short answer: Early blight is a fungus that makes brown spots with target rings on lower tomato leaves. Remove infected lower leaves, spray Southern Ag Liquid Copper Fungicide every 7-10 days, and don’t wet leaves when watering. It won’t cure leaves that are already spotted, but it stops it from spreading.

If you do nothing, all lower leaves will turn yellow and fall, and your plant will stop producing.

Quick Table – What To Do

Situation	What To Do
Few spots on lower leaves	Remove infected leaves, spray copper, every 7-10 days
Many leaves spotted, plant still alive	Remove worst leaves, spray copper + chlorothalonil, every 7 days
All leaves yellow, plant dying	Pull it out, don’t compost, disinfect tools

Concentric spots of Alternaria on a tomato leaf

How to Identify Early Blight – 3 Signs

1. Brown spots with target rings
Spots are brown, 1-2 cm, with concentric rings inside, like a target. That’s the sign that it’s Early Blight, not Septoria.

2. Starts on lower, older leaves
Early blight always starts at the bottom. Lower leaves get spots first, then it moves up. Upper leaves stay clean at first.

3. Leaves turn yellow, wither, fall
Heavily infected leaves turn yellow around the spots, wither, and fall off. Plant looks bare at the bottom.

Don’t confuse with:

Septoria – Small spots, 2-4 mm, no rings, many spots. Early Blight spots are bigger, with rings.
Late Blight – Large black wet spots, fast spreading in cool, wet weather, kills plant in days. Early Blight is slower, dry spots, with rings.
Bacterial Spot – Spots are raised, scabby, on fruit too. Early Blight is only on leaves, flat spots with rings.

Early blight attacks tomato, potato, eggplant, pepper.

Why It Happens

Alternaria solani is a fungus. It overwinters in plant debris and soil. Spores splash up from soil to lower leaves when you water or when it rains.

It likes:

Warm, wet weather – 25-30°C, wet leaves
Overhead watering – water splashes spores up
Crowded plants – no air flow, leaves stay wet
Lower leaves touching soil

_{Tomato fruit infested with Alternaria}

Treatment – What Works

Step 1 – Remove Infected Leaves

Pick off lower leaves with many spots. Put in plastic bag, throw in garbage. Don’t compost.

Wash hands and tools after.

Mulch around plants – 2-3 inches of straw or mulch – so soil doesn’t splash up to leaves.

_{Multiple concentric spots of Alternaria}

Step 2 – Spray Southern Ag Liquid Copper Fungicide – Best Treatment

Copper is the best treatment for early blight. It prevents spores from germinating. It doesn’t cure leaves that are already spotted, but it protects new leaves.

How to use: Mix 3-6 tsp per gallon. Spray all leaves, top and bottom, until runoff. Spray every 7-10 days. Re-spray after rain.

When to spray: Early morning or evening, not in heat above 30°C, not when bees are active.

Step 3 – For Heavy Infection – Chemical Fungicide

If more than half your leaves are spotted, copper alone is not enough. Add a chemical fungicide.

Active ingredients that work on early blight:

How to use: Mix as per label, spray every 7 days, 3 times. Rotate between copper and chemical – don’t use the same fungicide every time.

Prevention for Next Season

Water at base, not on leaves – Use drip irrigation or water at soil level
Mulch – 2-3 inches of mulch stops soil splash
Space plants – 2 feet between plants, good air flow
Remove debris – At end of season, remove all tomato plants, don’t leave them in soil
Rotate crops – Don’t plant tomatoes, potatoes, eggplant in same spot 2 years in a row
Spray early – Start copper spray when plants are young, before you see spots

What I Recommend

If few spots: Remove infected lower leaves, mulch, spray Southern Ag Liquid Copper every 7-10 days.

If many leaves spotted: Remove worst leaves, spray Copper + chemical fungicide, every 7 days, 3 times.

For next season: Mulch + drip irrigation + resistant varieties + early copper spray.

FAQ

Can I eat tomatoes from a plant with early blight?
Yes, if fruit is not infected. Early blight is only on leaves, not on fruit. Wash fruit well.

Will early blight kill my plant?
If you do nothing, yes – leaves fall, plant stops photosynthesizing, dies. If you spray early, plant recovers and produces.

Is early blight the same as late blight?
No. Early blight is slower, brown spots with rings, in warm weather. Late blight is faster, black wet spots, in cool wet weather, kills in days.

Should I pull out a plant with early blight?
No, unless all leaves are yellow and plant is dying. Early blight is manageable – remove lower leaves, spray copper, plant will keep producing.

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