Tomato & Potato Blight: Early vs. Late Blight

GardenDraft Team · June 17, 2026 · 6 min read

Part of: Plant Problems & Pest Guides

"Blight" gets blamed for almost any tomato leaf that turns brown, but two very different diseases hide behind the word — and they call for very different responses. One is a slow, manageable nuisance you'll see most years; the other is a fast-moving killer that can wipe out a tomato or potato patch in a week. Telling them apart is the first job.

Early blight: common and manageable

Early blight is the one most gardens see every season. It starts on the oldest, lowest leaves as small brown spots with concentric rings (a "bullseye" or target pattern) often ringed by a yellow halo. It creeps upward slowly as the season wears on, and while it can defoliate a plant and reduce yield, it rarely kills outright and it works from the bottom up. Because it overwinters in soil and crop debris and reaches the plant by rain-splash, the defenses are about keeping leaves off the dirt:

• Mulch to stop soil from splashing spores onto leaves (see mulching).
• Stake and prune for airflow, and strip the lowest leaves, exactly what pruning your tomatoes accomplishes.
• Water at the base, in the morning, never over the foliage.
• Rotate nightshades and clean up debris in fall (crop rotation).

Catch it early, remove affected lower leaves, and most plants carry a good crop despite it.

Late blight: the fast killer

Late blight is a different animal — the same disease behind the Irish potato famine, and it moves fast. It shows as large, greasy, gray-green to brown blotches on leaves and stems, often with a faint white fuzz on the leaf underside in humid weather, and it can blacken an entire plant in days. It doesn't reliably start at the bottom; it strikes anywhere. It spreads on the wind across whole regions during cool, wet spells, so it's not just your garden at stake.

Late blight is a community problem. If you suspect it, confirm with your local extension office, and if it's confirmed, remove and destroy affected plants immediately — bag them for the trash or bury them deep; do not compost. Leaving infected plants standing seeds the disease for every garden and farm downwind. Volunteer potatoes and tomatoes from last year are a common reservoir, so pull those too.

Prevention that covers both

The same habits blunt both diseases: resistant varieties where available, generous spacing and support for airflow, base watering, mulch, rotation, and fall cleanup. For early blight, copper or other approved fungicides can slow spread if applied early, but cultural practices do most of the work. For late blight, prevention and fast removal are the whole game — no home spray reliably saves an infected plant. If your leaves are curling or yellowing in some other pattern, work through the tomato leaf diagnosis guide first to be sure it's blight you're dealing with.