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R5 Corn Growth Stage and Scouting Tips
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R5 Stage*
(Begins 35 - 42 days after silking.)
At R5, all or nearly all kernels are dented or denting. The shelled cob is dark red. The kernels are drying down from the top, where a small hard layer of starch is forming. This starch layer appears shortly after denting as a line across the back of the kernel (the non-embryo side). With maturity, the hard starch layer and line will advance toward the cob. Accumulated starch is hard above the line but still soft below the line.
Tips*
- Stress at this stage will reduce yields by reducing kernel weight.
- At the beginning of R5, kernels have about 55% moisture content.
GDUs Required** to reach R1 growth stage depends on maturity and is approximately:
| CRM | GDUs |
|---|---|
| 80 | 1,735 |
| 90 | 1,960 |
| 100 | 2,185 |
| 110 | 2,410 |
| 120 | 2,640 |
| Scout for these Common Pests and Diseases | Timing* |
|---|---|
| Anthracnose Top Dieback | R3 through R5. |
| Anthracnose Stalk Rot | R5 through R6. |
| Diplodia Ear Rot | R5 through R6. |
| Diplodia Stalk Rot | R5 through R6. |
| European Corn Borer | Second-generation egg masses are laid in late-July through August. |
| 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. |
| Western Bean Cutworm | Scout ear tips for feeding. |
* 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.