Recent frost has damaged many acres of corn in the state. The extent of frost damage to corn will depend on the low temperature, duration of the low temperature and the maturity stage of the corn.

Frost-damaged corn can still be chopped for silage, says James Rogers, North Dakota State University Extension forage crops production specialist. However, the moisture content of the chopped corn must be at the right level for proper ensiling to occur. 

“Proper moisture content at the time of ensiling is key to achieving adequate fermentation of the silage and preservation,” says Rogers.

While frost-damaged corn will appear to dry quickly due to the rapid change in color from green to light green or gray, the moisture content of the corn may still be too high to ensile. If frost-damaged corn at the milk stage is harvested immediately after frost for silage, whole-plant moisture content could be too high. This will result in a wet and sour silage and a loss of nutrients due to excessive seepage, Rogers warns.

Optimal moisture concentration is needed for silage fermentation and preservation to occur. Targeting a whole-plant moisture content of 62%-68% at the time of silage chopping will result in optimal silage fermentation for most types of silage storage structures. While this is an ideal moisture content, corn will ensile at 75% moisture when placed in a bunker or trench silo. For a bag silo, a moisture range of 60%-70% will work.

Moisture content of the corn plant will vary by the stage of plant maturity when frost occurs. At the milk stage, whole-plant moisture content is around 80% and should be allowed to dry down to the optimal level for ensiling. By allowing corn at the milk stage to dry down to a lower moisture content, there will be some loss in dry matter yield but an improvement in silage quality.

“A caution with frost-damaged corn at the milk stage is the potential for mold development in the ears,” says Rogers. “Not all corn molds are harmful to livestock, but some can produce mycotoxins that can be.”

Corn at this stage could also have elevated nitrate levels, but if the corn is harvested for silage, nitrate levels are reduced.

Samples can be screened for mycotoxin levels at the NDSU Veterinary Diagnostic Laboratory (vdl.ndsu.edu).

Corn at the dough stage when frost occurs will have a moisture content of around 75% and may require a few days of drying to get down to the proper moisture content, depending upon the type of silo being used. At dent stage — when the milk line is halfway down the kernel — corn may be down to a whole-plant moisture content of 70%, but if frost occurs at mid- to late-dent, it should be harvested as soon as possible.

For more information about frost damage to a variety of crops, visit NDSU’s online resource: ndsu.ag/cropfrost25.

NDSU Agriculture Communication – Sept. 12, 2025

Source: James Rogers, 701-857-7682, james.rogers.1@ndsu.edu

Editor: Dominic Erickson, 701-231-5546, dominic.erickson@ndsu.edu