The early morning of June 25th brought unusually cold temperatures to many areas of North Central South Dakota. The low temperatures resulted in damage to corn fields across the region. In many cases the damage was restricted to low areas in the field and areas with heavy residue. Corn in affected areas ranged from 8 to 14 inches tall and damage to leaves was significant in many fields.
Growing points of young corn plants remain below ground until the corn is at the V5 growth stage. Most of the corn affected would have been past this growth stage. Frosts of this nature are associated with dry conditions when low humidity allows temperatures to cool more than normal during the night. Heavy residue cover contributes to this because it prevents soil moisture and soil warmth from moving to the atmosphere. One method used by many producers in the past was to wait 3-5 days before assessing the damage to corn. This allows plants time to recover if they are going to do so, especially if the weather is warm. It is possible to do a preliminary assessment of damage severity by splitting stalks and examining the growing point in different locations in the field. A white and firm growing point is a good indication that the growing point is alive. However, damage to leaves can restrict new growth on the corn giving the corn a twisted look and causing it to “buggy whip”. There has been some success in preventing this by mowing the corn off above the growing point. This is only effective if the areas are small. Check with the insurance agent first.
Even if a producer chooses to take the wait-and-see approach there are several things that need to be done as soon as possible. These include contacting the crop insurance agent to make them aware that a potential loss occurred. It is also important to check spray records for affected fields to see how the herbicide program will affect any potential planting decisions. There will definitely be increased potential for late-season weed issues. A good reference is the SDSU Extension 2017 Pest Management Guide for Corn.
It is probable that the damage occurred to areas in fields which had the best yield potential. Therefore, fertilizer application rates in damaged areas may need to be considered.
If damaged plant material recovers to some degree it may be more susceptible to bacterial diseases. Bacterial diseases can enter the plant through tissue wounds that result from frosts, hail or heavy winds. Nothing can be applied to the crops to prevent or limit bacterial diseases if they occur. Fungicides are only effective on fungal diseases.
It might be valuable to delineate the damaged areas using a mapping program and an ATV or even a drone where available. Having an accurate handle on the extent of the damage makes the decision process easier. A plan contingent on whether the plants recover or not can be developed. This should include checking for potential sources of seed. It is probably not prudent to leave large areas of fields with dead corn unseeded until next year. Widespread lack of forage for livestock may provide an opportunity to salvage some value from damaged areas. Information on annual forage options can be found in Annual Forages for Feed.
Source: Ruth Beck, iGrow