| AFFECTING WHOLE PLANT: |
|
CONDITION |
CAUSE |
 |
Seedlings
develop weak, water-soaked stems and fall over |
Damping-off
|
|
Wilted,
yellow plants |
Wireworm
|
|
Yellow,
wilting plants |
Fusarium yellows (Fusarium
oxysporum)
|
|
Yellow,
dying plants |
Onion or seedcorn maggot
|
|
| AFFECTING LEAVES: |
|
CONDITION |
CAUSE |
|
Yellow
leaves, slow growth |
Nitrogen deficiency
|
|
Yellow
leaves, dwarfed plants |
Aphids
|
|
Brown
leaf tips; white blotches on leaves |
Onion thrips
|
|
Tips of
leaves die, pale green to brown leaf spots; later leaves are black with
a purple, furry mold |
Downy mildew (Peronospora
effusa)
|
|
Leaf
tips turn brown and die |
Hot, dry weather
and/or excessive heat
|
|
Pale,
green-silvery leaf spots |
Can be a reaction to
excessive rain or hail
|
|
Papery,
white leaf spots with a characteristic lengthwise split; brown leaf tips |
Botrytis leaf blight
|
|
| AFFECTING BULBS: |
|
CONDITION |
CAUSE |
|
Gray,
water-soaked appearance of outer bulb scales |
Caused by high (>
85° F.) temperatures
|
|
Bleached,
soft bulbs |
Sunscald
|
|
Water-soaked,
soft bulbs |
Freezing injury
|
|
Roots
turn pinkish, shrivel and die |
Pink root
|
|
Sunken,
dry, brown-black areas around neck, rotted neck; gray mold on bulb
surface |
Neck rot
|
|
Dark-green
or black spots with concentric rings on bulb and neck |
Onion smudge
|
|
Rotted
bulb |
Purple blotch or
white rot
|
|
Poor
bulb formation, small size |
Potassium or nitrogen
deficiency, late planting, or Onion thrips
|
