Extension > Garden > Diagnose a problem > What's wrong with my plant? > Annuals and Perennials > Marigold > Leaves discolored brown to black
Marigold > Leaves > Leaves discolored brown to black
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White Mold
Sclerotinia sclerotiorum
- Entire plant or single branch wilts, leaves turn brown and die
- Wilted stems are discolored, tan to off-white
- Fluffy, white cotton-like fungal growth may been seen on infected plants when humidity is high
- Black hard spheres ranging in size from 1/16 to ½ inch can be found clinging to the outside an infected stem or embedded inside the dead stem
- Entire plant or single branch wilts, leaves turn brown and die
- More information on white mold
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Root rot
Rhizoctonia solani and Pythium spp.
- Leaves turn yellow and wilt
- Plants are stunted
- The base of the stem may turn brown and crack
- Roots have brown sunken areas and lack root hairs
- The outer root tissue may be easily removed leaving behind thin, stringy root cores
- Disease favors cool, wet soil with poor drainage
- Lab test necessary to distinguish between Rhizoctonia and Pythium Root Rot
- More information about Rhizoctonia root rot
- More information about Pythium root rot
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Gray Mold
Botrytis cinerea
- Irregular brown spots on leaves
- Brown blossoms or petals; flowers drop off prematurely
- Gray fuzzy mold develops on rotted tissue under humid conditions
- Disease develops during cool, wet weather
- More information on gray mold
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Cold Damage
- Leaves look water-soaked and soft, then turn black
- Injury appears immediately
- Occurs at temperatures below 50° F
- More information on cold damage
