Extension > Garden > Diagnose a problem > What's wrong with my plant? > Annuals and Perennials > Phlox > Discolored leaves
Phlox > Discolored leaves
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Powdery Mildew
Erysiphe cichoracearum
- Powdery, fluffy white spots and blothces on leaves, stems, and flower parts
- Tiny black round spheres may be visible within white spots late in the season
- Spots typically start on lower leaves but can spread to cover the entire plant
- Severely infected leaves may be completely covered in white or grayish white fungi
- In some cases, leaves become curled or twisted or turn yellow due to the infection
- More information on Powdery Mildew
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Aster Yellows
The Aster Yellows Phytoplasma
- Leaves and stems may be yellow, stunted and spindly
- Flowers are small and distorted, petals may remain all or mostly green
- A brush-like mass of weak shoots may arise from the stem
- Occurs most often in mid to late summer
- More information on Aster Yellows
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Leaf Drop
- Problem with water movement in some cultivars - not a disease
- Yellow or brown patches on leaves on old stems, often leaf veins remain green
- Older leaves on the lower part of the stem turn brown and dry up
- In severe cases leaves may fall off
- Occurs only on some cultivars
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Virus
Tomato spotted wilt, Tobacco rattle virus and others
- Yellow or light green rings, wavy lines or spots on leaves
- Leaves may be smaller than normal, plant may be short and grow poorly
- Lab test required to distinguish between viruses and verify infection
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Southern Blight
Sclerotium rolfsii
- Leaves turn yellow then brown from the edges inward and wilt
- The base of the stem may be brown or discolored
- Tiny tan to reddish brown hard spheres and white cottony growth can be seen at the base of infected leaves or in the soil around infected plants
- Often seen after warm wet weather
