Can early blight be cured once it starts?

The infected leaves cannot be healed, but the plant can usually be kept productive for the rest of the season, which is the realistic goal. Early blight builds slowly from the bottom of the plant upward, so if you remove the affected lower leaves early, mulch to stop soil splashing spores up, and protect the remaining foliage with a copper or chlorothalonil product, you can hold the disease below the fruit and still get a good harvest. What you are managing is progression, not reversal. Left alone, it defoliates from the ground up and exposes fruit to sunscald.

What does early blight look like on tomato leaves?

The signature is a dark brown spot with concentric rings inside it, like a tiny archery target or a tree-ring pattern, usually ringed by a yellow halo. Spots appear first on the oldest, lowest leaves because those are closest to the soil where the fungus overwinters, and they enlarge and merge until the whole leaf yellows and drops. You may also see dark, sunken lesions on stems and a leathery, dark rot at the stem end of fruit. The concentric rings are the feature that separates early blight from septoria leaf spot and from late blight.

Is early blight the same as late blight?

No, and confusing them leads to the wrong response. Early blight is caused by the fungus Alternaria and progresses slowly from the lower leaves, showing target-like rings; it is a manageable, season-long nuisance. Late blight is caused by the water mold Phytophthora infestans, spreads explosively in cool wet weather with large greasy gray-green blotches, and can kill a plant in days — it is the pathogen behind the Irish potato famine. Both hit tomatoes and potatoes, but the urgency and the products differ, so identify which you have before acting.

What is the best fungicide for early blight?

For a home garden, copper-based products and chlorothalonil are the workhorses, with mancozeb another effective protectant and Bacillus-based biofungicides available for a lower-toxicity program. All of these are protectants, meaning they defend healthy tissue rather than cure infected leaves, so timing and thorough coverage matter more than which one you pick. Rotate between different active ingredients through the season to slow resistance. Most important, read and follow the label — it will state the crops, the rate, and the days-to-harvest interval, and in the United States that label is legally binding.

How do I stop early blight coming back every year?

Break the cycle the fungus depends on. It overwinters on infected debris and in the soil, so clean up and dispose of tomato and potato residue at season's end and rotate these crops out of the same bed for two to three years. Mulch heavily to keep soil-borne spores from splashing onto lower leaves, space plants for airflow, stake or cage them off the ground, and water at the base in the morning. Choose tolerant varieties such as Mountain Magic, Iron Lady or Defiant, and remove the lowest leaves early as a routine habit.

How to Treat Early Blight on Tomatoes and Potatoes

Written & researched by Elena Marsh Gardening & Landscaping Editor

Updated March 2026

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To treat early blight, strip the affected lower leaves, mulch to stop soil splash, and protect the healthy foliage with copper or chlorothalonil. Early blight is a fungal disease (Alternaria solani) of tomatoes and potatoes that shows as dark, concentric target-ring spots starting on the oldest, lowest leaves and climbing the plant. You cannot heal infected leaves, but by removing them early, improving airflow, and applying a protectant on a schedule, you can keep the plant productive all season. Always follow the product label.

We do not test or physically handle the plants and products we cover; our guidance draws on horticultural extension research and the aggregated experience in thousands of owner reviews, as explained in how we rank.

What early blight is and how to confirm it

Early blight is caused by the fungus Alternaria solani (and closely related species). It infects tomatoes and potatoes, and occasionally other members of the nightshade family. The name is a little misleading — it does not necessarily strike early in the season, but it does tend to hit older, stressed foliage first.

The diagnostic sign is the leaf spot: a dark brown to black lesion with a series of concentric rings inside it, giving the classic bullseye or tree-ring appearance, usually surrounded by a yellow halo. These start on the lowest, oldest leaves — nearest the overwintering fungus in the soil — and enlarge until leaves yellow and die, with defoliation working steadily upward. On stems you may see dark, slightly sunken lesions, and at the fruit's stem end a firm, dark, leathery rot with the same ring pattern. On potatoes it also causes similar leaf lesions and shallow, dark tuber spots.

It favors warm temperatures with alternating wet and dry periods — dew, light rain, or overhead watering to wet the leaves, then warmth to drive infection. Stressed plants, poor soil fertility, and heavy fruit loads all make it worse.

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Telling early blight from its look-alikes

Three tomato leaf diseases get mixed up. Sorting them out points you at the right response.

Disease	Spot appearance	Speed	Pathogen
Early blight	Dark spots with concentric rings, yellow halo	Slow, bottom-up	Fungus (Alternaria)
Septoria leaf spot	Many small spots, tan centers, tiny black specks	Moderate, bottom-up	Fungus (Septoria)
Late blight	Large greasy gray-green blotches, white fuzz below	Explosive	Water mold (Phytophthora)

The concentric rings are early blight's signature. Lots of tiny spots peppered with black dots point to septoria — see how to treat septoria leaf spot. Large, fast, greasy blotches mean late blight, covered in how to treat tomato blight.

The treatment path, least-toxic first

Sanitation — Remove and dispose of infected lower leaves and any fruit with stem-end rot. Bag them; do not compost diseased tomato debris into your beds.
Cultural correction — Mulch heavily to block soil splash, since the fungus rides splashing water onto lower leaves. Stake or cage plants off the ground, thin for airflow, water at the base in the morning, and keep plants well fed so they are not stressed.
Organic protectants — Apply copper (copper hydroxide or copper octanoate) or a Bacillus-based biofungicide to healthy foliage, covering both leaf surfaces, and reapply per label after rain.
Broad protectant fungicides — For stronger protection, chlorothalonil or mancozeb are the standard home-garden choices, applied preventively and on schedule.
Rotate actives — Alternate between different active ingredients through the season to reduce the chance the fungus develops resistance.

Every one of these products works by protecting healthy tissue, not by curing infected leaves, so start early and keep coverage up through the wet stretches. And read the label: in the United States the pesticide label is legally binding under FIFRA, and it tells you the approved crops, the mixing rate, and the days-to-harvest interval you must respect before picking.

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Why mulch and lower-leaf removal do so much

Early blight overwinters in the soil and on last year's debris, and it gets onto the plant mainly by splashing — rain or irrigation hitting bare soil and throwing spore-laden droplets up onto the lowest leaves. Two cheap habits break that path. A thick mulch layer covers the soil so splashing is dramatically reduced. Removing the bottom several inches of foliage, so no leaves touch or sit near the ground, takes away the landing pads the spores need. Together they often do more than any spray, and they cost nothing but a few minutes.

Why plant vigor changes the outcome

Early blight is often described as a disease of stress, and that is more than a figure of speech. The fungus hits older and weaker tissue hardest, so a plant carrying a heavy fruit load, running short on nutrients, or struggling in poor soil loses its lower leaves far faster than a well-fed, vigorous one growing in the same garden. This is why two neighboring plants can show very different levels of disease from an identical spore source.

The takeaway is that feeding and watering a tomato properly is part of blight management, not separate from it. Keep the plant steadily supplied with moisture and appropriate nutrition so it holds its lower canopy longer and can outpace the disease climbing from below. Avoid the extremes — drought stress and waterlogged roots both weaken a plant and open the door — and mulch to even out soil moisture. A protectant program layered on top of a healthy plant works; the same program on a starved, stressed plant is fighting uphill. Vigor buys you time, and with early blight, time is what lets the plant ripen its crop before it defoliates.

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Early blight on potatoes

On potatoes, early blight produces the same ringed leaf lesions and, in a bad year, defoliation that cuts yield. It also causes dark, dry, sunken spots on tubers. Manage it the same way: rotate potatoes out of infected ground for two to three years, keep plants vigorous with adequate fertility since weak plants are hit hardest, hill and mulch to protect tubers, and use protectant fungicides where pressure is high. Harvest into dry conditions and cure tubers well, and discard any showing surface lesions rather than storing them.

Preventing it next season

Resistant and tolerant varieties — Mountain Magic, Iron Lady, Defiant and similar tomatoes tolerate early blight far better than heirlooms.
Crop rotation — keep tomatoes and potatoes out of the same bed for two to three years so soil inoculum declines.
Sanitation — clear and dispose of all nightshade debris at the end of the season.
Mulch — a permanent barrier against soil splash.
Spacing and support — cage or stake for airflow and to lift foliage off the soil.
Base watering in the morning — keep leaves dry and give any wetness time to evaporate.
Routine lower-leaf removal — take off the bottom leaves early as standard practice.

For the other diseases that hit the same plants, compare how to treat blossom end rot (a calcium and watering issue, not a disease) and the two blight pages linked above.

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How to Treat Early Blight