orn and soybean in parts of Indiana were damaged by frost in the wee hours of Mothers Day 2001. Air temperatures from most official weather reporting stations were in the 30s, but likely dropped into the 20s in lower lying areas, especially muck fields. As with any frost event, patience is a virtue when assessing the extent of damage to corn and soybean.
At young developmental stages, soybean is relatively more susceptible to above-ground frost damage than corn because of its exposed growing points whereas the growing point of corn remains below ground until the 5- to 6-leaf collar stage. Axillary buds exist at each leaf axil of a soybean plant, including the cotyledons. Recovery from frost damage can occur if any of these buds remain alive. Frost damage extending below the cotyledons translates to complete death of that seedling.
Little of the states corn crop is yet to the 5- to 6-leaf collar stage of development, so the consequences of the frost damage should be minor and limited to death of above-ground plant parts. Corn can easily recover from this type of damage early in its development and suffer no yield loss whatsoever. The fly in the ointment will be any low lying fields where temperatures actually dropped to lethal levels (28F or less). In this situation, even the below-ground growing point may have been exposed to damaging temperatures.
The key issue for assessing frost damage to either corn or soybean is the need to be patient and allow the plants to show you whether they are capable of recovering. The true extent of tissue damage may not be discernible a day or two after the frost event. The secret is to avoid looking at the damaged field(s) for three to five days. After that period of time, recovery of the surviving plants should be evident while those plants that are truly dead will not exhibit signs of recovery.
Signs of recovery in corn will be extension of fresh leaf material in the whorl. The dead tissue of the damaged part of the whorl may restrict this leaf extension for a while, but in most cases will not restrict it completely. Signs of recovery in soybean will be new leaves elongating from one or more of the axillary buds.