Dissection of a V9 plant shows many ear shoots (potential ears). These develop from every above-ground node except the last 6 to 8 nodes below the tassel. Lower ear shoots grow fast at first, but only the upper 1 or 2 develop a harvestable ear. The number of kernel rows is determined by V9. The tassel begins to develop rapidly. Stalks lengthen as the internodes grow. By V10, the time between new leaf stages shortens to about every 2 to 3 days. Total number of leaves will vary from 12 to over 20 depending on hybrid maturity and genetics. Hybrids of 120-125 CRM have the most total leaves.
The potential of kernels per row is determined by V12 to V15. The top ear shoot is still smaller than the lower ear shoots, but many of the upper ears are close to the same size. This is the start of the most crucial period for determining grain yield. Upper ear shoot development overshadows lower ear shoot development. Every 1 to 2 days, a new leaf stage occurs. Silks begin to grow from the upper ears. By V17 (110 CRM), the tips of upper ear shoots may be visible atop the leaf sheaths. The tip of the tassel also may be visible. Just before tasseling silks from the basal ear ovules elongate first. Silks from the ear tip ovules follow. Brace roots (aerial nodal roots) grow from the nodes above the soil surface to help support the plant and take in water and nutrients during the reproductive stages.
GDUs Required** to reach V9 growth stage depends on maturity and is approximately:
** Hybrid growth is influenced by the growing environment. Individual results may vary.
|Scout for these Common Pests and Diseases||Timing*|
|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.|
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.