| AFFECTING LEAVES AND HEADS: |
|
CONDITION
|
CAUSE
|
 |
Bleached
center leaves are dwarfed, curled or twisted |
Aster yellows (Phytoplasma)
|
|
Yellow
or pale leaves, stunted plants |
Leaf hoppers
|
|
Yellow,
distorted new growth |
Tarnished plant bug
(Lygus pratensis)
|
|
Yellow
leaves, slow growth, bitter taste |
Nitrogen deficiency
|
|
Yellow,
curled leaves |
Aphids
|
|
Light
green or yellow crinkled leaves with enlarged veins |
Big vein: caused by a
virus-like organism
|
|
Dull
gray-green to brown leaves |
Thrips
|
|
Mottled,
ruffled leaves; stunted plants |
Mosaic viruses
|
|
Leaf
margins turn brown and die |
Tipburn, prevalent in
hot weather
|
|
Browning
and dwarfing of plant; Velvety, white growth on leaves |
Downy Mildew
|
|
Powdery
dust on upper leaf surfaces |
Powdery mildew
|
|
Outer
leaf margins tan, blistering of leaves |
Freezing injury
|
|
Wilting,
sudden collapse of outer leaves on mature plants |
Sclerotinia drop
|
|
Lower
leaves and midribs rot near the base of the plant first |
Bottom rot or Rhizoctonia (Rhizoctonia
spp.)
|
|
Slimy,
rotted heads |
Gray Mold (Botrytis
cinerea)
|
|
Midrib
discolored |
High temperatures
(> 80° F.)
|
|
Lettuce
malformed |
Boron or phosphorus
deficiency
|
|
Brown
center and rosetting |
Calcium deficiency
|
|
Small
holes in leaves, shot-hole injury |
Flea beetles (Phyllotreta
spp.)
|
|
Large
hole in leaves; excrement found at base of head |
Cabbage looper, Imported cabbage worm
(Pieris rapae) , Beet
armyworm, and Corn
earworms (Heliothis zea)
|
|
Large
holes in leaves with slimy trails |
Slugs and snails
|
|
White or
translucent, irregular tunnels in leaves |
Leafminers
|
|
| AFFECTING WHOLE PLANT: |
|
CONDITION
|
CAUSE
|
|
Seed
doesn’t germinate |
High soil and/or air
temperatures
|
|
Seedlings
clipped off at soil line |
Cutworms (Noctuidae
spp.)
|
