Extension > Garden > Diagnose a problem > What's wrong with my plant? > Vegetable > Onion > Undersized or no bulb developed
Onion > Bulb > Undersized or no bulb developed
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Aster yellows
Aster Yellows Phytoplasma
- Plants may produce small bulbs
- Youngest leaves yellow from the base upwards
- Leaves become flattened and streaked yellow and green, and may become twisted
- Infected plants are randomly scattered through field
- More information on Aster Yellows
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Botrytis leaf blight
Botrytis squamosa
- Bulbs are not directly infected but may be smaller on plants with severe leaf damage
- Leaves develop small white circular to elliptical spots surrounded by a light green to silvery white halo
- Centers of the spots usually become sunken, straw colored, and may break apart in a lengthwise slit
- In cool (54-75F) wet weather, disease develops rapidly, entire plants dieback starting with the oldest leaves first
- More information on Botrytis Leaf Blight
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Nitrogen deficiency
- Plants may produce small bulbs
- Tips of leaves are yellow
- Entire plant appears pale green to yellow
- Stems are thin
- More information on Nitrogen Deficiency
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Onion yellow dwarf virus
Trichoplusia ni
- Bulbs fail to form if plants are infected when young or are firm but small when infected later in the season
- First see yellow streaks at the base of young leaves
- Eventually all leaves show yellow streaking to complete yellowing
- Leaves are crinkled, flattened and fall over
- Disease comes in on infected cloves or with the green peach aphid
- More information on Onion Yellow Dwarf Virus
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Pink root
Phoma terrestris
- Plants are stunted and may produce no to very small bulbs
- Sunken dark pink to maroon areas on roots
- Infected roots break off easily
- Leaves turn yellow with a reddish tinge from the tip down due to root damage
- Commonly occurs mid to late season, in areas with poor soil
- More information on Pink Root
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Downy mildew
Peronospora destructor
- Plants may produce small bulbs
- Leaves develop elongated pale green to tan spots
- Purplish gray fuzzy growth develops on leaves
- Severely infected leaves collapse and die
- Disease is most severe in cool wet weather
- More information on Downy Mildew
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Onion thrips
Thrips tabaci
- Bulbs can become distorted or undersized
- Whitish spots and streaks are present on leaves
- Leaves may become distorted
- 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
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Northern root knot nematode
Meloidogyne hapla
- Onion bulbs are unaffected but small when roots are severely infected
- Roots have small round galls
- Onion plant is stunted, leaves yellow and die early in the season
- More information on Northern Root Knot Nematode
