More Information on Frost Damage in Cereals

Two short articles on frost damage to crops were published in last week�s Crop and Pest Report. Nevertheless, given the pervasiveness and severity of the sub-freezing temperatures we experienced last week in North Dakota, I believe some additional information on frost damage to cereals is in order. Numerous factors affect how sub-freezing temperatures impact a crop; temperature alone does not always accurately predict damage.

Factors affecting frost damage - Some of the main factors that influence frost damage in cereal crops are: crop tolerance, growth stage, moisture content of the soil, duration of the sub-freezing temperature, location in the field, and environmental conditions before the occurrence of the sub-freezing temperature.

Crop - Cereal crops are generally considered to be frost tolerant early in their growth cycle. There is considerable variation for tolerance between crops, however. In general terms for the cereals grown in ND (and provided they are at the same stage of development), tolerance to freezing temperatures can be ranked in the following order: winter rye (most tolerant to frost) > winter wheat > oats > barley > wheat > corn (least tolerant).

Growth stage - One reason that cereals tolerate frost early in the season relative to broadleaf crops, is that their growing points remain below the surface of the soil for several weeks after emergence and are therefore protected from the extremes in the temperature of the air above. In small grains the growing point extends above the soil�s surface at about the 6 leaf stage or just prior to jointing and in corn at about the 5 leaf stage. Fortunately, all of the spring sown cereals in the state were still relatively young and their growing points were below the soil�s surface during last week�s cold weather. Winter wheat, however, has started to joint in parts of the state and is potentially more susceptible to frost damage than its spring sown counterpart. I would recommend that you carefully inspect growing points in your winter wheat if you had temperatures below 25 degrees for any extended period of time. The growing point is more susceptible to damage than leaf tissue during jointing. A damaged growing point will appear brownish or water soaked. A dead leaf may appear in the whorl if the growing point has been damaged.

Prolonged (or very low) sub-freezing temperatures can kill growing points of cereal crops even if they are below the surface of the soil. Corn is the most sensitive and temperatures of less than 28 degrees can be lethal.

Environmental factors - Temperatures change more slowly in wetter soils than in dryer soils. Therefore, there is more risk of low temperatures killing plants if your soils are also dry. Plants are capable of hardening themselves against freezing and plants that had previously been exposed to near freezing temperatures are more likely to tolerate lower sub-freezing temperatures than those that have not. Most of the cereal crops were probably at least partially hardened before the arrival of the coldest weather last week and this may explain why there is less reported damage to cereals than was anticipated. Cold air is heaver than warm air, so cold air will flow towards the lowest parts of your field, making frost damage more severe in these areas. When assessing frost damage, I would suggest that you visit the lowest spots of your farm first.

Foliage that has been damaged by frost will initially appear yellow and within a few days turn black usually towards the tips of the leaf first. If the growing point was not damaged, after 3 to 5 days of reasonably warm weather, new growth should appear from the whorl. If this occurs, then you can be assured that the growing point was not killed. Loss of leaf tissue at this early stage will have little if any effect on yield. For corn that has not yet emerged, I would suggest that you dig up a few seeds to check for germination and to see if the emerging seedling is viable. Seeds that had not germinated will not be adversely affected, but emerging seedlings could be killed if soil temperatures were very cold. I am happy to report that my colleagues have informed me that emerging corn seedlings are rarely killed by cold soil temperatures, even in ND!  As mentioned above, if you have winter wheat that was beginning to joint, I would also advise you to check the health of its growing point, even if you did not have excessive damage to the foliage.

Joel Ransom

Extension Agronomist - Cereal Crops

NDSU Extension Service, North Dakota State University of Agriculture and Applied Science, and U.S. Department of Agriculture cooperating. Sharon D. Anderson, Director, Fargo, North Dakota. Distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914. We offer our programs and facilities to all persons regardless of race, color, national origin, religion, sex, disability, age, Vietnam era veterans status, or sexual orientation; and are an equal opportunity employer.
This publication will be made available in alternative formats for people with disabilities upon request, 701/231-7881.

Back to previous page