May 14, 2009
Frost Damage What to Look For?
Small Grains: Are very tolerant to temperatures as low as 22 F and keep in
mind that the growing point is below the soil surface until the 5 leaf stage
to jointing. The only significant damage that could occur would be that if the
frost was hard enough to collapse the stem, which would cause the plant/stem to
wilt and most likely die. In most instances, wilted, dark green and discolored
leaves will be the normal appearance. Recovery usually is quick with a new leaf
emerging from the stem within 2 to 3 days with a normal green color.
Winter wheat/jointed (5/12 leaf): The extent of time that the plants were
subjected to the cold temperatures will be the issue. The worst case scenario
would be that the developing spikelets were injured to where no kernels will
develop in those spikes. This usually will be the top of the head and that area
will be white in color along with the awns.
Canola, Flax, Mustard: These crops can handle a frost of 24 degrees for a short
time with Canoga the most tolerant to the cold temperatures. Frosted
leaves/plants will have a dark green or black in color. If discolored or injured
we need to wait at least 2 - 3 days before any decisions are made to see if the
growing point is alive. Within 3 days, there should be a new leaf emerging from
the growing point located in the center of the plant. The best indication that
the plant has been killed by a frost is the stem. If the stem below the
cotyledons is wilted and doesn't straighten out within 48 hours of the frost,
the plant is most likely dead.
Pulse crops (field peas, lentils and chickpeas): Similar to small grains, the
growing point is below the soil surface to the fifth node stage or about the 4
inch height stage. If the stem is collapsed, wilted on the soil surface for 48
hours and regrowth has not occurred, that plant has most likely been killed.
Recovery is usually quick with the newest leaf emerging from the stem within 3
days.
Corn: Corn plants less than 6 inches tall (V-5) or less will recover from frost
because the growing point is still below the soil surface and usually not
damaged. Lethal cold temperature is a concern since a corn plants growing point
region is relatively protected from the effects of simple frost while it remains
below the soil surface. Lethal cold temperatures for corn is 28 F or less.
