Corn Diagnostic Guide - 8-10 Leaves to Tasseling



Possible Cause(s)

Severe wilting and/or death of plants Sudden death of plants
  • Lightning - plants in an approximately circular area suddenly killed
Plants discolored Yellowing of plants, beginning with lower leaves
  • Nitrogen deficiency
  • Drought conditions
  • Ponded conditions - standing water
  Yellowing or leaf margins, beginning at tips; affected tissue later turns brown and dies
  • Potassium Deficiency
  Purpling or reddening of leaves from tip backward; affects lower leaves initially; leaf tips may later turn dark brown and die.
  • Phosphorus deficiency
  Yellow to white interveinal striping on leaves
  • Genetic stripe
  • Magnesium deficiency
  • Boron deficiency
  Pale green to white stripes between leaf veins, usually on upper leaves
  • Iron deficiency
  Upper leaves show pale green to yellow interveinal discoloration; lower leaves appear olive green and somewhat streaked.
  • Manganese deficiency
Plants discolored and malformed Plants show stunting and/or a mottle or fine chlorotic stripes in leaves
  • Maize dwarf mosaic or Maize dwarf chlorotic
  Stunting, tillering; twisting and rolling of leaves. Yellow and striped leaves; narrow leaves; upright habit
  • Crazy top
  • Sorghum downy mildew
  Plants darker green; stalks twisted at mid to upper half.
  • Herbicide injury
Plants malformed and/or lodged Plants show 'buggy-whip' effect - upper plant portion tightly rolled, enclosing upper leaves and tassel; plant elbowing or lodging
  • Herbicide injury - also may result in upcurling of brace roots and brittleness or lower nodes
  • mechanical injury
  Twisting and bending at corn stalks above the ear shoot; ear may be malformed
  • Herbicide injury
  • Mechanical injury
  • Hybrid characteristic
  Plants lodge or grow up in a 'goosneck' shape.
  • Corn rootworm larvae feeding damage - damaged root systems result in entire plant becoming lodged
  • Nematode feeding damage
  • Herbicide injury
  • Mechanical injury
  • Hot, dry weather and winds - preventing normal brace root development
  Brown, soft rot of a lower internode; stalks twist and fall.
  • Pythium stalk rot or bacterial stalk rot
  • European Corn Borer - stalks weakened by borer feeding damage
  • Stalk Borer Damage
  • Herbicide injury
  Soft, glistening white galls soon become black and dusty; on stalks, leaves, ear or tassel
  • Common smut
Plant tissue removed Ragged holes in the leaves and shredding of plants.
  • Hail Damage
  Shredding, tearing of leaves
  • Wind damage
  Longitudinal slits chewed out from between leaf veins.
  • Cereal leaf beetles - adult feeding damage
  Green, upper layer of tissue stripped from leaves.
  • Western Corn Rootworm Beetle Damage
  Leaf tissue skeletonized or lacy in appearance.
  • Japanese beetles
  "Window effect" of leaves - interior of leaves eaten out.
  • Corn blotch leafminers
  Leaves entirely eaten off or large areas of leaf tissue removed
  • Armyworm Damage
  • Grasshopper Damage
  • Fall Armyworm
  • Livestock
  Holes bored into stalks and area within stalk hollowed out by feeding damage
  • European Corn Borer - late instar
  • Stalk Borer Damage
  • Billbug larvae feeding damage
Lesions on plants Tan, oval to circular lesions
  • Holcus Spot
  • Fungal leaf spots
  • Paraquat herbicide injury
  Irregular to elliptical brown, water-soaked leaf spots
  • Bacterial leaf spot and stripe
  Small, circular tan spots with brown to purple margin.
  • Eyespot
  Brown, oval leasions with yellow to reddish brown borders
  • Corn Anthracnose
  Circular to oval, brown to black pustules on leaves
  • Common Rust


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.

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