Extension > Garden > Diagnose a problem > What's wrong with my plant? > Annuals and Perennials > Zinnia > Leaves discolored white, yellow or pale green
Zinnia > Leaves > Leaves discolored white, yellow or pale green
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Powdery Mildew
Golovinomyces (syn. Erysiphe) cichoracearum
- Powdery, fluffy white spots and blotches 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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Spider Mites
Tetranychus urticae
- Active during summer, particularly abundant during hot, dry weather
- Pale stippling appears on the upper leaf surface
- Leaves are discolored off-green to whitish, yellowish, or bronze
- Premature leaf drop can occur
- Visible webbing occurs on infected leaves when populations are high
- Adults are tiny (1/50th inch long) and oval, greenish or yellowish with a dark spot on either side of the body
- More information on Spider Mites
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Aster Yellows
Phytoplasma
- Part or all of the leaves may turn yellow
- Flowers fail to develop, remain small green and may be distorted
- Clumps of weak shoots known as witches broom develop throughout the plant or on flower stalks
- More information on Aster Yellows
