Jenny Rees
Extension Educator, Clay Center
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.
Source : unl.edu