Corn Diagnostic Guide - Emergence to 8-10 Leaves

 

Appearance

Symptoms

Possible Cause(s)

Scattered dead or poorly growing plants Uneven growth (see Uneven Corn)
  • Soil compaction
  • Variation in planting depth, soil moisture, etc.
  • Drainage problems
  • Poor growing conditions
    • cold
    • wet
    • dry
  • Cloddy seedbed
  • Anhydrous or aqua ammonia injury
  Slow growth
  • Low fertility
  • Cold (mainly below 55 degrees F)
  • Dry
  Plants stunted, wilted and/or discolored
  • Fertilizer injury
  • Corn Nematodes
  • Herbicide injury
  • Anhydrous or aqua ammonia injury
  • Damping off and seedling blights
  • Stewart's Bacterial Wilt
  Plants cut off above or below ground level or rapid wilting
  • Black Cutworm
  • Wireworm
  Sudden death of plants
  • Frost in low areas of field
  • Lightning
Wilting Upper leaves roll and appear dull or sometimes purple; stunting of plants; plants may die
  • Drought conditions
  • Insect damages
    • Black Cutworm
    • Chinch bugs
    • Garden symphylans
    • White grubs
    • Grape Colaspis grubs
    • Wireworms
    • Corn root aphid
  • Mechanical damage due to root pruning by cultivator
  Whorl dead
  • Wireworm
  • Hop vine borer
  • Black Cutworm
  • Common Stalk Borer
  Crown roots not developing
  • Dry surface soil
  • Shallow planting depth
  • Wind
Discolored Plants Pale green color
  • Nitrogen deficiency
  • Sulfur deficiency
  • Water logged soil
  Yellow or dying leaf edges
  • Potassium deficiency
  Yellowing of upper leaves
  • Magnesium deficiency
  Yellowing of lower leaves
  • Excessive moisture
  Purpling or reddening of leaves from tip backward
  • Phosphorus deficiency
  • Soil compaction
  • Cold weather
  • Hybrid characteristics
  • Injured, broken leaves
  • Insects
    • Grape Colaspis grub
    • White grub
    • Garden symphylans
  • Herbicide injury
  Whitish or yellow striping between leaf veins
  • Nutrient deficiency
    • Magnesium
    • Iron
    • Manganese
    • Boron
  • Low pH or acid soil condition
  Whitish striping along leaf veins
  • Sulfur deficiency
  White areas in the center and towards base of leaves
  • Zinc deficiency
  Lower leaves dead, tips dying on upper leaves
  • Fertilizer injury or burn (nitrogen and potash too close)
  Leaves appear sandblasted; pale green or whitish in color
  • Wind damage
  • Thrips
  • Spider mites
  Yellowing or browing beginning from leaf tips
  • Excessive herbicide rates
  Leaves turn white to tan and die
  • Herbicide Injury
  Light and dark mottling or mosaic on leaves
  • Maize dwarf mosaic virus (MDMV) or maize chlorotic dwarf virus (MCDV)
  Yellow to white strips with smooth margins running length of leaves
  • Genetic stripe
  Bleached bands across leaf blades; leaf tips may die back; leaf collapse and fold downward
  • Herbicide injury
  • Air pollution
Discolored and stunted plants Yellow leaves; spindly, stunted plants
  • Nitrogen deficiency
  • Sulfur deficiency (more pronounced on younger leaves)
  Purple or red discoloration of leaves, especially leaf margins; stunting; stubby, malformed roots; drouthy appearance
  • Herbicide injury
  • Phosphorus deficiency
Discolored, stunted and/or malformed Tillering, stunting
  • Crazy top
  Yellow-green tint; severely stunted; inability of leaves to emerge or unfold
  • Herbicide injury
  Leaves yellow and not expanded; roots sheared off or dried up
  • Shallow application of ahydrous ammonia
  Yellow strips in leaves, stunting
  • Sorghum downy mildew
  Leaves fail to unfurl properly, often underground; plants may be lodged, lying flat on ground
  • Herbicide injury
  Leaves stunted and twisted and may appear knotted
  • Herbicide injury
  Shoots and roots malformed; onion-leafing (leaves remain wrapped)
  • Herbicide injury
  Plants bent or twisted; stunted; irregular row of holes in unfolded leaves
  • Stalk Borer Damage
  • Corn Billbug
Lesions on leaves Spots of dead tissue on leaves
  • Herbicide injury
  Oval, circular or rectangular lesions on leaves
  • Helminthosporium leaf spot
  Long, irregular yellow to brown streaks in leaves
  • Stewart's bacterial leaf blight
  Tan, spindle-shape lesions with parallel sides and buff to brown borders
  • Southern corn leaf blight
  Oblong, oval, tan colored spots with yellowing of leaves
  • Yellow leaf blight
  Brown, oval lesions; yellow to reddish-brown
  • Anthracnose leaf blight
  Small transluscent, circular to oval lesions
  • Eyespot
  Circular to oval cinnamon-brown pustules
  • Common Rust
Plant tissue missing or removed Plant cut off at ground level
  • Black Cutworm
  • Sod webworm
  Leaves eaten off or large areas of leaf tissue removed
  • Armyworm Damage
  • Grasshopper Damage
  Ragged leaves shredded or torn
  • Wind or Hail Damage
  Rows of circular to elliptical holes across leaves (shothole affect)
  • European Corn Borer
  • Stalk Borer Damage
  • Corn Billbug
  Ragged holes in leaves
  • Black Cutworm, Cutworms
  Longitudinal slits chewed out from between leaf veins
  • Cereal leaf beetles
  Irregular brown lines or tracks scratched from the top layer of leaf tissue
  • Corn flea beetles
  "Window effect" of leaves - interior leaves eaten out
  • Corn blotch leaf miners
  Yellow, weakened area on leaf mid-rib from tunneling feeding damage
  • European Corn Borer

 

Planting to Emergence || Emergence to 8-10 Leaves || 8-10 Leaves to Tasseling || Tasseling to Maturity || Corn Diagnostic Guide


Adapted by James H. Hill, Iowa State University - Hancock County Extension Education Director, from information prepared by Dale M. Studt, retired ISU Extension Crop Production Specialist.

Share |