Onion > Leaves > Leaves flattened or distorted
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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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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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- 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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Stem and bulb nematode
- 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 ...