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Diagnose Guide for Corn Problems (Emergence to V7 (Yellow, white areas in…
Diagnose Guide for Corn Problems
Before Emergence
No plant emerged
No seed planted
Planter Problems
Seed not sprouted
Ammonia Injury
Seed not viable
Fertilizer in contact with seed
Insect or disease
Lack of oxygen
Seed normal, not swelled
Soil too dry
Seed swelled, not sprouted
Soil dried out
Soil too wet
Seed not viable
Rotted Seed or seedlings
Seed rot
Pythium
Diplodia
Gibberella
Fusarium
Colletotrichum
Sprout twisted or leaves expanded underground
Mechanical Injury
Seed too deep
Chloroacetemide herbide injury
Cloddy Soil
Insecticide injurt
Fertilizer burn
Biuret damage
Seed eaten, dug up, or sprout cut off
Seeds hollowed out
Insect damage
Seed Corn Maggot
Wireworm
Seed corn beetle
Thief ant
Flea beetle larvae
Plants pulled up or eaten
Bird Damage: Crows, pheasants, blackbirds
Rodent damage: Mice, voles, ground squirrels
Knee High (V7) to Tassel
Plants have abnormal shape or position
Plants lean or fall over
Rootworm
Strong winds before the brace roots formed
Nematodes
2,4-D herbicide injury
Mechanical Injury
Stalks collapse from rot
European Corn Borer
2,4-D herbicide injury
Cutworm
Brace roots malformed or missing
Herbicide Injury
2,4-D , dicamba
Slugs
Stalks collapse from stalk rot
Pythium stalk rot
Bacterial stalk rot
Plants malformed and discolored
Stunting, tillering, twisting
Crazy tops disease
Galls, red leaves, excessive silvering
Smut
Narrow leaves striping
Sorghum downy mildew
Stunning, red leaves, excessive silvering
Maize dwarf mosaic
Corn stunt
Maize chlorotic mottle
Plants discollored: white, yellow or purple on leaves
Leaves completely white
Extreme Heat
White stripes and some white leaves on scattered plants
Genetic stripe
Yellowing of plants, beginning with lower leaves at leaf tip among midrib
Nitrogen deficiency
Standing water
Interveinal chlorosis or purpling
Amino Acid Synthesis Inhibitor
Purpling or reddening of leaves, from tipping backwards; effects lower leaves initially; leaf tips may turn dark brown and die
Phosphorus deficiency
Yellowing of leaf margins, beginning at tips; tissue turns brown and dies
Potassium deficiency
Yellowing and necrosis of lower leaves at beginning of leaf tip
Herbicide injury
Purple or reddening of leaves from tip backwards; leaf tips can turn dark and die
Phosphorus deficiency
Yellow to white interveinal stripping on leaves or reddening of leaves
Magnesium deficiency
Pale green to white striping on leaves
Iron deficiency
Upper leaves show pale green to yellow interveinal discoloration
Magnese Deficiency
Lesion spots on leaves
Photosynthetic inhibitor herbicided
Foliar Deseases
Yellow Leaf Blight
Anthracnose
Stewart's Leaf Blight
Helminthosporium Leaf Blight
Leaves have a window effect, but neither surface is broken
Corn blotch leafminer
Leafhopper eggs
Upper leaves brown and sticky
Corn leaf aphids
Yellow or dead leaves or plants
Ammonia burn
Glyphosate herbicide injury
Holes in leaves
Leaves eaten
Armyworm
Variegrated cutworm
Stalk Borer
European corn borer
Southwestern Corn Borer
Grasshopper
Cutworm
Livestock or wildlife
Western corn rootworm (adult)
Leaves shredded
Hail Injury
Wind damage
Silking to Maturity
No silks apparent
Delayed silking or failure to silk
Population too high for hybrid
Drought stress
Low phosphorus supply
Nitrogen deficiancy
Severe corn leaf aphid
Silks eaten off
Grasshopper
Corn rootworm adult
Japanese beetle
Woollybear caterpillar
No pollen tassels sterile
Improper kernel set
Leaves torn or pieces missing
Large, irregular eaten in leaves
Grasshopper
Damage to ear
Shucks eaten or open, kernels eaten or damaged
Kernels tunneled and eaten
Ends of ears eaten off
Grasshopper and corn aphid Insects::
Discolored or dead plants
Reddish or purple leaves and stalk
Genetic character
Drought or other stress
Corn stunt
Maize corn mosaic
Corn leaf aphids
Nematodes
Plant dies prematurely
Stalk rot
Corn borer
Drought
Dead frosted appearance of plants
Frost
Foliar diseases: Leaf blights, Anthracnose
Barren stalk, no ears
Population too high for hybrid or season
Low fertility, especially nitrogen
Drought
Corn leaf aphids
Ear smut
Extreme heat in pollination
Nematodes
Emergence to V7
Scatters spots of dead or poorly growing plants
Uneven growth
Uneven drainage
Poor growing conditions
Ammonia injury
Dead or Stunned
Insect Damage
Garden sympylan
White Grub
Wireworm
Stewarts leaf blight
Ammonia Injury
Cultivator Injury
Nematodes
Glyphosate
Small area of dead plants
Plants missing
Problem at or near planting
Dead plants present
Lightening
Cultivator Injury
Plant tissue removed
Window pane effect, leaf skeletonizing
Insect damage
cereal leaf beetle
Grape Collaspis
Red-headed flea beetle
Palestriped flea beetle
Southern Corn Rootworm Adult
Large holes in leaves
Variegated cutworm
Sod webworm
Common stalk borer
Slug
Leaf Margins Damaged
Yellow striped armyworm
Armyworm
Fall armyworm
Row of holes across leaves
Wireworm
Cutworm
Armyworm
Billbug
Shredding or tearing of leaves
Wind, hail damage
Yellow, white areas in leaf
Plant mostly white
Genetic Mutation
Drift or carrier
Isoxafutole, mesotrione, clomazne
Whitish or yellowing striping between leaf veins
Nutrient deficiency
Iron
Magnese
Magnesium
Boron
Low pH
Only on occasional plants
Physiological Injury
Necrotic stripes between veins
Stewart's Leaf Blight
Whitish stripping along veins
Sulfur Deficiency
Leaves appear sand blasted or speckles, tips shredded
Thrips
Wind damage
Broad white areas in center toward base of leaves, stunning, failure on internodes to elongate
Narrow whitish scratches in leaf surface
Corn flea beetle
Plants discolored and stunted
Lower leaves dead, tips dying on upper leaves
Fertilizer Injury
Chinch bug
Pale green color
Waterlogged soils
Glyohisate drift injury
Nitrogen deficiency
Leaf edges yellow or dead
Potassium deficiency
Leaves Purplish or reddish, especially at tips
Wind damage
Cold soils
Grape colaspis
White Grub
Wireworm
Nematode
Dull gray areas on upper leaves, often where leaf bends
Frost or intense sunlight
Plants twisted or broken off
Thiocarbamate herbicide injury
Cultivator damage
Insecticide injury
Yellow leaves, plants weak
Nitrogen deficiency
Sulfur deciciency
Plants irregularly shaped, broken or wilted
Plants twisted or broken off
Thiocarbamate herbicide injury
High acetamide herbicide rates
Cultivator damage
Insecticide injury
Leaves appear water soaked to grayish becoming necrotic
Ammonia Injury
Frost
Paraquat Injury
Leaves rolled, plants wilted
Drought stress
Root Feeding Insects
Corn root aphid
White Grub
Garden Symphylan
Grape colaspis
Corn rootworm
Mechanical Injury to Root
Nematodes
Leaves tightly rolled, not wilted
Herbicide Injury
2,4-D, dicamba
Chloroacetamide herbicide
Plants suddenly wilt and die or cut off at a ground level
Insect Damage
Wireworm
Black cutworm
Mature to Harvest
Stalks broken
Below the ear
Stalk rot
Diplodia
Pythium
Gibberella
Charcoal
Anthracnose
Weak stalks; potassium deficiency
Southwestern Corn Borer
Broken mainly above the ear
European Corn Borer
Anthracnose top dieback
Ears on ground
Shank broken, whole ear dropped
Racoon or squirrel
European Corn Borer Damage
Ears fallen from husks
Hybrid character
Stalk Rot
Rot or damage on ears or kernels
Whole ear or large section
Ear Rots
Diplodia
Gibberella
Nigrospora
Physalospora
Gray Ear Rot
Deer
Birds
Small areas on the ear or individual kernels
Ear Rots
Fusarium
Penicillium
Aspergillus
Insect Damage
Fall Armyworm
Corn Borer
Corn Earworm
Red stripes on kernels
Kernel Red Streak
Hybrid Character
