Different Kinds of Tomato Blight and How to Tell Them Apart

• Early blight
• Late blight
• Septoria leaf spot

They’re each caused by a different fungus. You can tell these three problems apart by what they look like, what parts of the tomato they affect, and when their symptoms appear. But the good news is this: all three can be treated and controlled similarly with biofungicides or fungicides and by practicing good preventative care.

	Early Blight	Late Blight	Septoria
Photo	Photo: University of Minnesota Extension	Photo: Iowa State University	Photo: Cornell University
Cause	fungus: Alternaria solani	fungus: Phytophthora infestans	fungus: Septoria lycopersici
Characteristics	Dark, concentric spots ¼ - ½” on lower leaves and stems Spots on fruit near stems Lower leaves yellow and drop	Blue-gray spots on leaves which turn brown Dropped leaves Irregular brown, greasy spots on fruit White mold rings on spots	Small black or brown spots on the lower leaves Lower leaves yellow and drop
Parts affected	leaves stem fruit	leaves stem fruit	leaves stem
Timing	early- to mid-season in wet weather	mid- to late-season in wet weather	early- to mid-season in wet weather

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