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Extension > Garden > Diagnose a problem > What's wrong with my plant? > Annuals and Perennials > Zinnia > Spots or blotches on leaves

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Zinnia > Leaves > Spots or blotches on leaves

1 of 5
  • Powdery mildew 1
  • Powdery mildew 2
  • Powdery mildew 3

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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  • Bacterial leaf spot 1
  • Bacterial leaf spot 2
  • Bacterial leaf spot 3

Bacterial Leaf Spot
Xanthomonas campestris pv. zinniae

  • Small brown to black angular spots surrounded by yellow halos on leaves
  • Spots on petals are reddish and circular
  • Spots may merge together creating larger dead black areas that dry and crack
  • Disease starts on lower leaves and progresses up the plant
  • More information on Bacterial Leaf Spot (3.46 MB PDF)
3 of 5
  • Four-lined plant bug damage 1
  • Four-lined plant bug 2
  • Four-lined plant bug 3

Four-Lined Plant Bug

  • Present May to early July
  • Feeding causes brownish, round sunken spots on leaves
  • Nymphs are red or red and black; adults are greenish yellow with 4 black stripes, ¼ to 1/3 inch long
  • More information on Four-Lined Plant Bugs
4 of 5
  • Alternaria blight 1
  • Alternaria blight 2
  • Alternaria blight 3

Alternaria Blight
Alternaria zinniae

  • Reddish brown circular spots up to ½ inch in diameter appear on leaves and petals
  • Centers of spots turn grayish white
  • Center of an older spot may fall out giving the leaf a shot-hole appearance
  • Severely infected leaves, stems, and flowers turn brown and die
  • Dark brown sunken lesions (cankers) are common on the stem near the soil line
  • Warm, wet or humid weather favors disease
  • More information on Alternaria Blight (3.46 MB PDF)
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  • Gray mold 1
  • Gray mold 2
  • Gray mold 3

Gray mold
Botrytis cinerea

  • Large brown spots or blotches on leaves
  • Leaves or entire plant may be completely blighted, brown and wilted
  • Blossoms or petals may turn brown and drop off prematurely
  • Gray fuzzy mold develops on rotted tissue under humid conditions
  • Disease develops during cool, wet weather
  • Commonly on seedlings and young transplants
  • More information on gray mold

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