Cereal: Other Crop Problems
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811: Agronomy Guide > Cereals
> Other Crop Problems
Recommended treatments to control insects, pests and diseases can
be found in OMAFRA
Publication 812, Field Crop Protection Guide.
Winter cereals can be destroyed during the winter and early spring
period by frost heaving, ice, low temperatures and snow mould. Varieties
differ in their ability to withstand these different winter stresses.
This explains the regional adaptation of some varieties that may
not perform well across the province.
The freeze/thaw cycles of early spring are one of the main reasons for winterkill in Ontario. As frost goes into the ground, it works under the crown and "lifts" the plant up Plate 28. If these freeze/thaw cycles are repeated enough times, the plant is ejected or "jacked" out of the soil. Roots are broken and left exposed above the soil, causing death of the plant due to desiccation. This process is referred to as frost heaving.
Deep-seeded wheat is not more resistant to frost-heaving injury.
The primary root system does not anchor the plant in the soil. The
secondary root system anchors the wheat plant in the soil, protecting
against frost-heaving injury. The secondary root system of the wheat
plant cannot develop deeper in the soil than the depth of the seed
Days to Emergence at Various Seeding Depths. When wheat is seeded
deep, the plant develops the crown and secondary root system at
about 2 cm (3/4 in.) deep, as the crown develops in response to
light. Regardless of planting depth, the secondary roots will not
develop below 2 cm (3/4 in.). To maximize resistance to frost heaving,
wheat plants need an extensive secondary root system developed as
deep as possible.
When a rapid snow melt or winter rain is followed by below-freezing
temperatures, ice can form as a thick sheet across ponded areas.
Even when the water is able to drain away below the ice sheet, the
ice itself may prevent oxygen from getting to the plants and the
wheat will suffocate and die below the ice.
Surface and subsurface drainage can help reduce the ponding, which
leads to this problem. Should an ice sheet form (for example, during
January and February), dormant wheat will only survive for approximately
2 weeks. Break the ice surface to allow gas exchange and to keep
the wheat alive.
Wheat will survive extremely cold temperatures before plant death
occurs. Plants that have "hardened off" (gone dormant)
can survive temperatures down to -24°C. Snow cover acts to insulate
the crop from extremely cold temperatures, and even 7.5 cm (3 in.)
of snow is sufficient to protect the crop from colder temperatures.
Leaf tissue on plants that have not hardened off will withstand
-9°C, making late spring frosts of little consequence. There
was only 1 year in the last century when cold temperatures in Ontario
destroyed the wheat crop.
While the wheat crop survives cold temperatures well, cold injury
can reduce vigour and final yield.
For more information:
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