Identifying frost in wheat

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In the event of severe frost, monitoring needs to occur for up to two weeks after the event to detect all the damage.

Accurate assessment of frost damage can help with decisions about whether and when to cut for hay or leave for grain harvest. An inspection five to 10 days after the frost event will reveal whether grain development has been affected.

If affected, the heads will feel soft and spongy when squeezed between thumb and forefinger. It is important to note that frosted paddocks can contain all of the symptoms detailed below because earlier cold damage may go undetected until a serious frost prompts a paddock inspection.

Photo of frost-damaged heads

Frost-damaged heads

Cold conditions and frost can damage florets during booting and render them sterile.

Photo of frost-affected plant stemsPhoto of frost-affected wheat stems

Frost-affected stems

A pale green to white ring on the stems of plants indicates they have been frost-affected. With good soil moisture crops can develop grain even with frost-damaged stems – but it is important to monitor for two weeks after the frost event.

Photo of healthy and frosted grain

Healthy and frosted grain

Sound grain (first left). Frosted grain is pinched and creased along the axis (as if long-nosed pliers have crimped the grain). Creases are regular not random. Grain may have a blue/grey appearance.

Photo of wheat anther

Photo of wheat anther

Healthy endosperm (top) and frosted endosperm (bottom).

Photo of healthy wheat anthers

Healthy (non-frosted) bright yellow anthers

Peel back the husk to inspect the condition of the floral organs in the head.

Photo of a frosted wheat anther

Frosted banana-shaped anther

Pollen sacs (anthers) are normally bright yellow, but become dry, banana-shaped and turn pale yellow or white following frost.

Photo of frost-damaged heads

Frost-damaged heads

Peel open the floret and inspect the developing grain. Frosted wheat heads appear bleached and grain fails to develop.

Photo of healthy developing grain

Healthy developing grain

Peel open the floret and inspect the developing grain. Healthy developing grain is light to dark green, plump and exudes a white milky dough when squeezed. Frosted developing grain is white, turns brown and has a dimpled and crimped appearance.

Photo of wheat

Emerging wheat head

A frost-damaged floret on an emerging head. Exposed florets cannot tolerate low temperatures and will usually be sterile.

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Region National, North, South, West