The early start to planting season has heightened concern in some areas about the possiblity of frost damage. University of Illinois crop sciences professor Emerson Nafziger says most of the corn planted before April 1 was up and growing by the time it frosted the second week of April in central and northern Illinois. Two days after the freeze event, "severe damage was visible on the early-planted corn, with most or all of the above-ground leaf area dead," according to a press release from the university.
Nafziger pointed out, "when corn suffers frost injury at this stage, we normally assure ourselves that, with the growing point protected beneath the soil surface, the potential for regrowth back into normal plants is high." But he continued, "we are finding that most damaged plants are very slow to send out new leaf tissue, and some are making no regrowth at all. These are essentially dead, and even those that make some slow regrowth are not likely to turn into productive plants."
Nafziger points to a similar event in early May 2005, when about one-third of the plants died while the rest slowly regrew following a frost event. The yields from the earliest planted corn in 2005 were less than half that of the later planted corn grown at the same population.
While there's no telling whether the recovery of the frost-bitten 2012 crop in areas of Illinois will be better, Nafziger points out, "we do have the advantage that it's still early enough to allow us to watch the crop for another week or so before we need to make the decision to replant."
The big question is whether damaged plants will be healthy enough to produce as much as they normally would, according to Nafziger. He explains, "physiological damage, coupled with the slow growth of roots and tops due to loss of leaf area, may irreparably decrease the productive potential of plants. Damaged plants are already showing slow growth, and they will be overtaken in size by later-planted corn."
If evaluation of plant stands and cost benefits do show replanting is necessary, the next concern will be securing replant seed. Nafziger says this year, finding replant seed of good hybrids may not be easy and could be costly.