Agronomic Bulletin
Assessing Frost Damage to Corn
Understanding Frost Damage
The first step in determining frost and freeze damage is
to understand the temperatures at which damage
occurs and how the extremes of temperature and
duration can affect crops.
The minimum daily temperature during a 24-hour
period will usually occur just after sunrise. This cold air
normally settles into the low-lying areas of waterways
and depressions in the field where it affects crops first.
Water normally freezes at 32 degrees Fahrenheit. Leaf
tissue can freeze at temperatures two to three degrees
above that level, through a process called radiative
cooling, if the nighttime sky is clear and winds are calm.
Symptoms of Frost Damage
The effects of freezing temperatures will not show up
immediately. Leaf tissue that has been exposed to
freezing temperatures will begin to take on a silver color
approximately 4 to 6 hours after the temperature
returns to normal.
The frozen tissue may become white or light green in
color approximately 30 hours after exposure. In the
days following the freeze the tissue will progress
through several color changes and will eventually
become dark brown or black. Damaged tissue will
eventually become dry and break off the remaining
plant.
Frost damage to leaf tissue of young corn plants may
not be yield limiting. Young corn plants can lose all or
nearly all of their leaf tissue and fully recover with little
or no yield loss. This of course is assuming normal
maturity due to a normal frost date. If the frost damage
occurs prior to the fifth leaf (V5) stage the growing
point is usually below ground and protected from the
freezing temperatures.
Recovery of corn plants after a freeze will depend on
the temperature and moisture content of the soil.
When regrowth begins it will be evident in the whorl
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area. With adequate moisture and warmer soils plants
will recover more rapidly than in cold soils. Lack of
moisture will diminish recovery in warm soils and even
more in cold soils.
One of the concerns growers may have is that if there
are dead leaves at the top of the plant or in the whorl.
New leaves may not unfurl properly due to the dead
leaf material remaining tight and unwound. After 3
major late frost events in the mid 80’s, late 90’s and
again 2008, the question of mowing off the dead
material has arisen. In each case there was no
difference in yield between mowing the dead material
and plants that the leaves were left to grow through the
dead material. Keep in mind that the cut on the plant
will need to “heal” before development will begin again.
The concern of tassels not being able to emerge and
shed pollen may come up. Lack pollen shed is hardly a
factor as a tassel will produce 2-5 million pollen grains
contained in 2-6000 anthers. This equates to 2-5,000
pollen grains per kernel where only one pollen grain is
required per kernel.
Source: American Psychopathological Society
Determining Damage to the Growing Point
The growing point of the corn seedling is located below
ground until the plant is about ten inches tall. The
location of the growing point can be determined by
digging up the plant and carefully splitting the stalk
DYNA-GRO AGRONOMY SERVICES
©Copyright 2012. This information may have been accumulated from publicly available sources outside of Dyna-Gro Seeds, or its affiliates. Individual results may vary, and performance may
vary from location to location and from year to year. This result may not be an indicator of results you may obtain as local growing, soil and weather conditions may vary. Dyna-Gro® is a
registered trademark of Loveland Products, Inc. Featured logos are service/trademarks of their respective owners.
Agronomic Bulletin
lengthwise from the upper leaves through the root
crown. The growing point is the whitish area showing
layers of tissue arranged into a cone-like shape. The
growing point is normally unaffected if it was below the
soil surface at the time of the freeze. However, very
cold temperatures of 32 degrees Fahrenheit or colder
for several hours can penetrate the upper soil surface
and damage or kill the growing point of a young plant
even when it is below the soil surface.
To get an accurate estimate of the extent of damage,
observe and sample plants from at least three parts of
the field. Determine original plant stand by counting
healthy plants
Table 1: Row Length
in 1/1000th of
Required for 1/1000th Acre
an acre (see
15”
=
34’ 10”
Table 1) in at
20”
=
26’ 1”
least three
locations.
30”
=
17’ 5”
36”
=
14’ 5”
Determine the
38”
=
13’
8”
average
population of
the healthy plants. Repeat the same procedure in the
areas affected by the freeze. Determine the percent
yield loss due to stand reduction from Table 2.
If the growing point was at or above the soil surface at
the time of the frost the growing point will begin to turn
brown and become soft within about three to four days
after exposure.
Determining if Replanting is needed
It is always best to wait three to four days after a frost
to determine the extent of the damage, especially if the
growing point was at or near the soil surface at the time
of the frost. If a hard freeze occurs to older plants, it is
best to replant quickly to take advantage of the
remainder of the growing season.
Compare the cost of replanting the affected areas,
including seed, chemical, machinery and labor costs to
the potential yield of the replanted areas. The cost
benefit of replanting should be clearly positive to justify
replanting. If the potential return is marginal or
negative the areas should be left undisturbed.
Table 2: Percent Yield Loss of Corn Due to Uniform Stand Reduction.
Original
Stand
Remaining Corn Stand After Freeze Damage (1,000 plants/acre)
32,000
32
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
31,000
0
1
2
3
4
5
6
7
8
9
11
13
16
18
21
23
26
29
32
0
1
2
3
4
5
6
7
8
10
12
14
16
19
21
24
27
30
0
1
2
3
4
5
6
7
9
11
12
14
17
20
23
25
28
0
1
2
3
4
5
7
9
10
12
14
16
19
21
24
27
0
1
2
3
4
6
7
9
10
12
14
16
18
21
24
0
1
2
3
5
6
7
8
10
12
14
16
19
22
0
1
2
3
4
6
6
8
10
12
14
17
20
0
1
2
3
4
5
6
9
10
12
15
18
0
1
2
3
4
5
8
9
11
14
17
30,000
29,000
28,000
27,000
26,000
25,000
24,000
23,000
AGRONOMY BULLETIN
Page 2 of 2
DYNA-GRO AGRONOMY SERVICES
©Copyright 2012. This information may have been accumulated from publicly available sources outside of Dyna-Gro Seeds, or its affiliates. Individual results may vary, and performance may
vary from location to location and from year to year. This result may not be an indicator of results you may obtain as local growing, soil and weather conditions may vary. Dyna-Gro® is a
registered trademark of Loveland Products, Inc. Featured logos are service/trademarks of their respective owners.