R1 to R6
Katelin and April
No Silk apparent
Delayed silking or failure to silk
Silks eaten off
Insect damage
Grasshopper 
Japanese beetle
Corn rootworm adult
Wollybear caterpillar
Low phosphorus supply
Nitrogen deficiency
Drought stress
Severe corn leaf aphid
Population too high for hybrid
No pollen; tassels sterile
Improper kernel set
2,4-D or Dicamba applied at improper time
Genetic male sterility
Leaves torn or pieces missing
Large, irregular areas eaten in leaves
Insect damage
Fall armyworm
Grasshopper
Damage to Ear
Kernels tunneled and eaten
End of ears eaten off
Shucks eaten or open, kernels eaten or damaged
Birds
Rodents or other animals
Grasshoppers
Insect damage
Picnic beetle
Corn sap beetle
Corn borer
Fall armyworm
Corn Earworm
Deer, Livestock
Discolored or dead plants
Dead, frosted appearance of leaves
Barren stalk, no ears, only stunted nubbins or scattered kernels
Plants die prematurely
Reddish or purple leaves and stalk
Population too high for hybrid or season
Low fertility, especially nitrogen
Drought
Corn leaf aphid
Ear Smut
Maize dwarf mosaic, other viruses
Extreme heat prior to or during pollination
Nematodes
Foliar disease
Helminthosporium leaf blights
Frost
Stewart's leaf blight
Anthracnose
Severe corn borer damage or other stalk injury
Drought
Stalk Rot
Corn stunt
Maize dwarf mosaic or other virus
Injury to leaf or stalk
Stress by corn leaf aphids
Drought or other stress-see barren stalks
Nematodes
Genetic Character