R3 Corn Growth Stage and Scouting Tips

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R3 Corn Growth Stage - Milk

R3 Stage: Milk* 
(Begins 18 - 22 days after silking.)

The R3 kernel is yellow outside, while the inner fluid is now milky white due to accumulating starch. The embryo is growing rapidly. Most of the R3 kernel has grown out from the surrounding cob. Silks are brown and dry or becoming dry.


  • The kernels, well into their rapid rate of dry matter accumulation, are about 80% moisture. Cell division within the endosperm is essentially complete, so growth is mostly due to cell expansion and starch-fill.
  • Final yield depends on the number of kernels that develop and the final size or weight of the kernels.
  • Stress can still impact yield by reducing both factors.

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

80 1,405
90 1,580
100 1,760
110 1,940
120 2,120
** Hybrid growth is influenced by the growing environment. Individual results may vary.

Scout for these Common Pests and Diseases Timing*
Anthracnose Top Dieback R3 through R5.
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.