Assessing freeze, frost damage: What to look for, when to look for it

MACOMB, Ill. — Weather can be unpredictable, so there’s always a risk for freeze or frost injury to corn and soybean plants.

The two plants handle freezing temperatures differently. Corn plants die immediately when growing point tissue freezes.

Soybean plant tissue is more tolerant of freezing temperatures. However, temperatures below 32 degrees can damage leaves, and extended temperatures below 30 degrees can damage stems, pods and seeds.

The severity of damage depends on the growth stage of the soybeans, the temperature and the duration of exposure, said Brad Mason, Pioneer field agronomist.

In soybeans, a freeze that damages stems, pods and seeds can reduce the yield and crop quality. Frost-damaged corn is susceptible to leaf loss, which reduces the photosynthetic area available to produce carbohydrates for new plant growth.

“If a frost occurs, wait five days before getting into the field and checking how the frost impacted the plants,” Mason said.

“While you may find dead tissue on the plants, the growing point on the plant will be a good indication of survival. If the growing point is below the soil, it should be better protected from the frost.”

Mason checks on coarse soils first, after a frost.

“Those (coarse) soils typically have low organic matter, they typically don’t warm up, and if they do they cool off quick,” he said. “Go check those fields. They don’t radiate nearly as much heat.”

No-till fields may also be at a disadvantage when it comes to heat absorption, Mason said. No-till fields are a good starting point for analyzing potential damage.

Recovery from early-season death of above-ground tissue depends on:

• Stage of growth — Potential for recovery is higher at VE-V2 than for V3-V4 stages because energy reserves still exist in the seed to support growth.

• Amount of green tissue remaining — The more green tissue there is for the plant to live on until there is enough re-growth for photosynthesis, the higher the potential for recovery, especially at V3-V4 stages when seed reserves are nearly depleted.

• Weather conditions during re-growth — Dry, warm conditions are more favorable than cold and wet weather.

• Number of frost events — Plants at this stage will often recover from one episode, but reserves can be depleted with multiple frosts while damaged seedlings are recovering.

The probability that plants will not recover or that the stand will contain non-competitive “runts” is increased with repeated frost damage/recovery cycles.

When frost damage occurs, several management options are available. If damage is light, growers may choose to do nothing and allow plants to recover.

More severely damaged fields may need to be replanted. Replanting decisions should only be considered after carefully examining frost-damaged plants and assessing plant stands.