Early Blight
Risk near you, next 48h
See whether your local forecast favours this disease right now.
When it strikes
Treat, then re-check in 5–7 days
Pick off the worst material, apply the organic option below, and look again after five to seven days. If the spread continued, escalate rather than repeating the same treatment.
Rain and irrigation splash
Water splashing off soil and infected leaves carries it upward and along the row. Watering at the base and mulching the soil surface break the route.
It carries over to next season in soil, debris or seed — which is why rotation matters here, not just treatment.
Keep out of the compost
This survives a garden heap. Bag it for municipal green waste, which is composted industrially at temperatures a garden heap cannot reach, or burn it where that is permitted.
When and where to look
Scout the planting while temperatures hold between 20°C and 32°C, with humidity above 75%, after rain or heavy dew, while the leaves are still wet. Risk builds after roughly 8 unbroken hours of those conditions, so the morning after such a night is the moment to look.
Rule these out first
Same category, and at least one host crop in common — so they are genuinely confusable in the same part of the garden.
The signs that lead here
Full problem lists for these crops
About
Early blight (Alternaria solani) is a common warm-season disease of tomato and potato that builds through summer, starting on the oldest leaves and working upward, reducing yield and exposing fruit to sunscald.
Symptoms
Brown spots with concentric rings forming a target or bullseye pattern, surrounded by yellow halos, on older lower leaves first. Severe defoliation and dark leathery lesions near the stem end of fruit.
Organic Treatment
Remove affected lower leaves, mulch to stop soil splash, and spray copper or a Bacillus subtilis biofungicide. Maintain even watering and adequate nitrogen to slow progression.
Chemical Treatment
Chlorothalonil or mancozeb every 7–10 days, alternating with strobilurin (azoxystrobin) or difenoconazole during heavy pressure.
Prevention
Rotate crops on a 2–3 year cycle, mulch beneath plants, stake for airflow, and avoid overhead irrigation. Choose tolerant cultivars where available.
Crops at risk
Related problems
Early Blight risk by location
Each location has a month-by-month profile computed from the weather archive: how many hours a year actually meet this disease’s thresholds.