Check Growth Stage as You Make Cropping Decisions

Check Growth Stage as You Make Cropping Decisions

7-leaf corn comparison Figure 1: Two corn plants from the same field. The left plant received frost damage to the first few leaves which died; the plant on the right was unaffected by the frost. Both plants are at the 7-leaf stage which was determined by slitting open the stems. (Photo courtesy of Rachel Stevens)

Two corn ears, one damage by pesticide Figure 2: Photo of two corn ears where pesticides were applied based on height. The ear on the left was from a field where pesticide (in this case, a late post-emergence herbicide) was applied at the correct growth stage. The ear on the right is from an adjacent field. It was similar in height but two growth stages ahead of the corn on the left. Pesticide application at the later growth stage resulted in stunted ears to plants throughout the field. (Photo courtesy of Jenny Rees).

Corn damaged by the May 15-17 freeze grew back in many Nebraska fields; however, a noticeable size difference can be observed in areas where plants lost leaves from frost compared to those that didn't. 

Figure 1 shows two corn plants from the same field. The left one was affected by the frost while the right one was not. In this case, both plants are at the 7-leaf growth stage despite their height difference. Their growth stage was determined by splitting the stems and assessing the number of nodes visible within that stem.  This resource from Purdue University has good visuals to show how this can be done for early-season corn. 

Knowing correct growth stage is especially important in the case of pesticide applications where labels specify growth stage restrictions to ensure crop safety. Figure 2 shows ears from two adjacent fields whose plants were at the same height but different growth stages. One of the fields (Figure 2, right ear) was two growth stages ahead of the other field (Figure 2, left ear). 

Applying pesticide at the incorrect crop growth stage resulted in stunted ears on plants throughout the second field.

Thus, it's important to split open those stems, check your crop growth stage as you make your cropping decisions, and read and follow all pesticide label instructions.

Jenny Rees
Extension Educator, Clay Center