R2 Corn Growth Stage and Scouting Tips

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R2 Corn Growth Stage - Blister

R2 Stage: Blister*
(Begins 10 - 14 days after silking.)

R2 kernels are white on the outside and resemble a blister. The endosperm and its now-abundant inner fluid are clear. The embryo is still developing, but it now contains a developing miniature corn plant. Much of the kernel has grown out from the surrounding cob materials. The cob is close to full size. Silks are darkening and beginning to dry out. Starch has just begun to accumulate in the watery endosperm. Kernels are beginning to accumulate dry matter. Seed-fill is beginning.


  • Nitrogen and phosphorus are accumulating rapidly and relocating from vegetative to reproductive parts of the plant
  • The kernels are about 85% moisture and will dry down from this point.

GDUs Required** to reach R1 growth stage depends on maturity and is approximately:

80 1,305
90 1,470
100 1,635
110 1,800
120 1,965
** Hybrid growth is influenced by the growing environment. Individual results may vary.

Scout for these Common Pests and Diseases Timing*
Common Rust V12 through R4.***
Corn Rootworm Larval feeding is most extensive in early through mid-July in most regions of the Corn Belt.
European Corn Borer As the true stalk develops and European corn borer larvae increase in size, larvae can be found tunneling into the stalk.
Eyespot V6 through R4. Disease primarily found in northern environments.
Goss's Wilt VE through R6. Disease primarily found in Nebraska and portions of other western states.
Gray Leaf Spot VT through R4.***
Northern Leaf Blight VT through R4.***
Southern Leaf Blight VT through R4.***
Stewart's Wilt Disease is initiated with corn flea beetle feeding from VE to V5. Leaf symptoms appear after R1.
Western Bean Cutworm Initiate scouting based on local pheromone trap captures of adults. If trap data are unavailable, begin scouting at VT.
Click on the insect or disease for more information.

* Information from Pioneer and Iowa State University Extension.

*** Scout for these diseases earlier in seed production fields.

Use this information as a guide and it should not be the only factor in making decisions.