Q: 

Will dead leaf tissue wrapped around green, healthy leaves cause problems for future corn growth.

A:

Figure 1. Frost-damaged corn with dying outer leaf tissue. (Photo by Jenny Rees)

The recent widespread frost throughout Nebraska on May 15 and 17 followed by windy days resulted in corn plants looking like the one in Figure 1.  Leaf tissue exposed to temperatures below 30°F and in cases down to 28°F resulted in burst plant cells. Eventually injured leaf tissue turned brown and died.  Even though the growing point of corn is below ground until the six-leaf (V6) stage, 28°F is cold enough to potentially kill growing points. A common question this week has been if the dead leaf tissue that is wrapped around green, healthy leaves will cause problems for future growth.

A study conducted by Roger Elmore and Ben Doupnik, Jr. in south central Nebraska in 1992 looked at three experimental treatments to frost-injured corn at the 3-leaf growth stage:

1. Allowing plants to naturally recover (control treatment)
2. Clipping the corn plants
3. Replanting

The experiment was conducted in three fields with natural frost-induced leaf defoliation levels of 55%, 70%, and 100%.  All treatments yielded similarly in the 70% defoliated site.  Replanting yielded 22%-92% more at the 100% defoliated site but reduced yield 37% at the 55% defoliated site.  Clipping corn plants after frost was an unreliable method of recovery.  It allowed for the spread of a bacterium (Pseudomonas fluorescens), which is not usually pathogenic to corn, but caused soft rot in this case.  In the 1992 study, unfavorable weather conditions for plant recovery prevailed for several days following the frost. Plants continued to die for several weeks at two of the sites. The decision of whether to replant was best based on extent of initial damage and plant recovery after the frost event.

Often frost-damaged necrotic tissue will break off in the wind, allowing growth to resume normally.  Where several leaves are wrapped together around the stem, new growth may struggle to grow through the dead tissue for a period of four days to two weeks.  In many cases, plants will recover from buggy whipping.  We encourage you to slit open stems and examine the growing point.  Healthy growing points are yellow-white in color and firm; they should not be soft and mushy.  We also encourage you to consider your replant options carefully.  An earlier CropWatch article provides a table to estimate yield potential based on date planted and percent stand.

Fortunately, weather conditions following this year's frost probably were more conducive for regrowth than those following the 1992 frost event.  In any case, scout fields now after the plants have had an opportunity to recover.

Jenny Rees, UNL Extension Educator
Roger Elmore, UNL Cropping Systems Specialist