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Extension > Garden > Diagnose a problem > What's wrong with my plant? > Vegetable > Onion > Leaves flattened or distorted

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Onion > Leaves > Leaves flattened or distorted

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  • Image: Aster Yellows

Aster yellows
Aster Yellows Phytoplasma

  • Leaves become flattened and streaked yellow and green, and may become twisted
  • Youngest leaves yellow from the base upwards
  • Bulbs may be small
  • Infected plants are randomly scattered through field
  • More information on Aster Yellows ...
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  • Image: Onion Yellow Dwarf Virus 1
  • Image: Onion Yellow Dwarf Virus 2

Onion yellow dwarf virus

  • Leaves are crinkled, flattened and fall over
  • First see yellow streaks at the base of young leaves
  • Eventually all leaves show yellow streaking to complete yellowing
  • Bulbs fail to form if plants are infected when young or are firm but small when infected later in the season
  • Disease comes in on infected cloves or with the green peach aphid
  • More information on Onion Yellow Dwarf Virus ...
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  • Image: Onion Thrips 1
  • Image: Onion Thrips 2
  • Image: Onion Thrips 3

Onion thrips
Thrips tabaci

  • Leaves may become distorted
  • Whitish spots and streaks are present on leaves
  • Eventually results in a silvery-white stippled appearance sometimes referred to as white blast or silver top
  • Bulbs can become distorted or undersized
  • Thrips are very small (< 1/20 inch) and a pale yellow color
  • Thrips are found feeding on the interior of the onion neck and on developing leaves
  • More information on Onion Thrips (pdf) ...
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  • Image: Stem and Bulb Nematode 1
  • Image: Stem and Bulb Nematode 2

Stem and bulb nematode
Ditylenchus dipsaci

  • Leaves are twisted and stunted
  • In severe infestations, plant may wilt and die
  • Bulbs are often desiccated and light weight, secondary rot organisms like soft rot may invade and rot the bulb
  • Outer layer of bulb is split or has cracks
  • More information on Stem and Bulb Nematode ...

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