Extension > Garden > Diagnose a problem > What's wrong with my plant? > Vegetable > Tomato > Dark spots on stems
Tomato > Stem > Dark spots on stems
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Early Blight
Alternaria solani
- Infects leaves, stems and fruit
- Black leathery spots on fruit start on stem end
- Dark irregular leaf spots, often surrounded by yellow tissue
- Sunken dark round stem lesion with concentric circles inside
- Occurs in warm wet weather, common at the end of summer
- More information on managing plant diseases in the home garden
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White Mold
Sclerotinia sclerotiorum
- Dark, firm water-soaked lesion on stem
- Girdled stems die and turn bone white
- Inside dead stems are black mouse poop shaped sclerotia
- Fruit are soft and rotted
- Cottony white mycelia inside and outside infected stems when humidity is high
- Favored by cool humid conditions
- More information on managing plant diseases in the home garden
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Late Blight
Phytophthora infestans
- Irregular watersoaked lesions on leaves, turn olive then brown
- Leaves, stems and petioles turn brown and shrivel
- Fruit spot is round olive colored, can cover whole fruit
- Infected tissue is covered with white mycelia is wet weather
- Disease spreads very rapidly in cool wet weather
- More information on managing plant diseases in the home garden
