Best to be patient when dealing with corn plants hit by frost
With temperatures hovering in the low 90s, it's hard to believe that less than two weeks ago, farmers and gardeners listened nervously as frost warnings were issued around the state.
Following reports of widespread frost over the Memorial Day weekend, UW Madison Agronomist Joe Lauer's phone began blowing up with texts from crop consultants whose clients wondered about the effect of the May 28 frost on corn yield.
The question was, "Should they replant?" Lauer says the short answer is "No."
"This frost event was a relatively early, correctable event that has caused a lot of anxiety, especially with above average corn prices. However, it is best to be patient," he said. "The growing point for corn is below ground and is often well insulated from freezing temperatures."
Lauer says that most plant leaf damage caused by the recent frost is observed in fields with lighter soils, that were no-till, that had cover crops, and/or were along edges of waterways.
"Most plants are recovering with new leaves emerging, although the recovery process has been slower than I anticipated," Lauer said.
With hot, humid temperatures up in the 90s, Lauer says that new leaves should emerge.
"If new leaves do not appear, then the plant has died," he said.
However, this does not mean that the field must be replanted. Lauer directs producers to follow guidelines from the UW publication, "Corn replant/late-plant decisions in Wisconsin."
Although late May's frost killed emerged corn leaves, the effect on yield will be negligible.
"By now, nearly a (two weeks) after the frost, corn plants should be showing newly emerging leaves," Lauer said. "There may be some tie-up of the leaves with the killed leaves, but eventually these newly emerged leaves will unfurl, and development will continue normally."
Through the years, Lauer says the University of Wisconsin has done numerous leaf clipping studies removing 100% of the leaves and measuring its effect against an untreated check.
In most years, corn grain yield was not affected when 100% of plants were defoliated between V1 and V4 stages.
"On average there was a 7% yield decrease, however, the effect was significant in only 2 of 7 years that the experiment was conducted," Lauer said.
Additionally, hail adjuster tables do not even begin adjusting for yield until the V7 stage of crop development.