R6 Corn Growth Stage and Scouting Tips
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R6 Stage: Physiological Maturity*
(Begins 55 - 65 days after silking.)
By the R6 stage, kernels have attained their maximum dry weight or dry matter accumulation. The hard starch layer has advanced completely to the cob. A black or brown abscission layer forms, moving progressively from the tip ear kernels to the basal kernels of the ear. It's a good indication of physiological maturity and signals the end of kernel growth. The husks and many leaves are no longer green, although the stalk may be.
Tips*
- A hard early frost before the R6 stage may halt dry matter accumulation and cause premature black layer formation. This could reduce yields by causing delays in harvest (frost-damaged corn is slower to dry.)
- To reduce potential frost problems, choose a hybrid that matures about 3 weeks before the average date of the first killing frost.
- Kernel moisture averages 30 to 35%, but this can vary considerably between hybrids and environmental conditions. Safe storage requires 13 to 15% moisture.
GDUs Required** to reach R1 growth stage depends on maturity and is approximately:
| CRM | GDUs |
|---|---|
| 80 | 1,895 |
| 90 | 2,145 |
| 100 | 2,390 |
| 110 | 2,640 |
| 120 | 2,890 |
| Scout for these Common Pests and Diseases | Timing* |
|---|---|
| Anthracnose Stalk Rot | R5 through R6. |
| Diplodia Ear Rot | R5 through R6. |
| Diplodia Stalk Rot | R5 through R6. |
| Fusarium Ear Rot | R5 through R6. |
| Fusarium Stalk Rot | R5 through R6. |
| Gibberella Ear Rot | R5 through R6. |
| Gibberella Stalk Rot | R5 through R6. |
| Stewart's Wilt | Disease is initiated with corn flea beetle feeding from VE to V5. Leaf symptoms appear after R1. |
Click on the insect or disease for more information.
* Information from Pioneer and Iowa State University Extension.
Use this information as a guide and it should not be the only factor in making decisions.