Key Considerations for Corn

  1. The growing point is below ground until the plant has 5 visible collars – this is 7 leaf corn.  Most Ontario corn would have not progressed this far by the morning of May 23, 2015.
  2. Tissue damage may be significant across many parts of the province but growing points should be undamaged.
  3. Growing points, when unaffected, should be firm, and yellow or light green in colour.
  4. New growth will emerge from the whorl and recovery should be complete.  In some cases the new growth gets obstructed by a dead tissue “knot” but this is mostly cosmetic and rarely causes a lasting problem.
  5. In some fields where frost damage was severe and soils were dry and loose, damage may have moved down the stem and killed the growing point.  Careful evaluation of these situations should be made over the next day or two to determine if replanting is necessary.

(See pictures to the right)

Key Considerations for Soybeans

  1. The growing point is above ground from the time of emergence. The growing point at the top of the plant is a group of rapidly dividing cells where new leaves are forming. This growing point is part of the "shoot apex". Other similar groups of cells are located in each leaf axil and may be sites for re-growth when the uppermost growing point is damaged by frost.
  2. Tissue damage in soybeans is now observed in many areas.  No-till, high residue fields tend to be more affected as the residue insulates the plant from the heat of the soil.  Sandy soils, muck soils and low topography areas are also impacted more severely.
  3. When the apex growing point and upper leaves are frozen, there is still capacity in the soybean plant to send out new leaves from buds that exist in the axils (points where the leaf attaches to the main stem) of the leaves or the cotyledons.  Regrowth in these plants is likely, but may depend on the energy reserves that still exist in the cotyledons.  Replanting is most likely not required, but fields should be monitored for regrowth.
  4. If frost damage extends down the stem below the cotyledons, it is likely that all buds have been damaged and no regrowth is possible.  Replanting will be required.

(See pictures to the right)

For further information, contact your Maizex representative.

Greg Stewart, Maizex Agronomy Lead