Leek
Symptom Cause  
Sunken spots on leaves; later, a purplish mold develops over spots
Downy Mildew
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Plant grows slowly; turn yellow; wilt, die
Onion Maggot
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White streaks, blotches on leaves; tips distorted, plants wilt, wither, brown, die
Onion Thrips
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Roots turn pinkish or red, eventually rot; plant is stunted with wilted tops
Pink Rot
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Block spots on leaves/between the sections of the bulbs; plants have twisted leaves
Smut (fungus)
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