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Frost Update

Vintage: 16 June 1998

This update depicts the recovery of corn plants after various levels of frost damage (see Figures 1 to 4 in "Frost damage in Corn") and the impact on the recovery of mowing the upper part of the whorl of frost-damaged corn.

Frost-damaged corn is recovering after 6 days of day-time temperatures in the mid twenties and some much needed rain. Where frost damage has been extensive, the greatest problem will most likely be "onion leafing", when expansion of the leaves is restricted by dead tissue in the whorl. In a survey of affected fields around Guelph on Sunday 14 June, incidence of dead growing points were found to be rare.

Corn growth 10 days after frost

  1. Leaf stage was 5 or less (leaf-tip method) when frost occurred (Fig. 1): new leaves emerge and "onion leafing" should not be a problem.
  2. Leaf stage was greater than 5 when frost occurred and
    1. Only leaf-tip damage, whorl was not frozen (Fig. 2): effects of frost will disappear quickly.
    2. Only top part of the whorl was frozen (Fig. 3): some "onion leafing" will occur but plants will survive. Mowing the dead whorl tissue may alleviate effects of frost damage (see below).
    3. If the lower part of the pseudostem (whorl) was still green, but the rest of the plant was frozen, deformations have occurred due to attempts by the growing point to push through dead tissue of the whorl (Fig. 4); it is not clear yet whether plants will be able to recover from the frost damage and mowing appears to have been benificial to its recovery.

Mowing frost-damaged corn
Corn grown by weed scientists at the Elora Research Station was at the 8- to 9-leaf stage when frost occurred. This corn was greatly damaged by the frost, although the growing point was not killed (Fig. 5). Most of the corn was mowed at about 5 cm (2") above soil level on Tuesday 9 June. On Sunday 14 June (5 days after mowing), the corn that had been mowed appeared to be in good condition (Fig. 6). Some rows were not mowed (Fig. 4) in order to illustrate the impact of mowing on plant recovery. A comparison of mowed (Fig. 7, right frame) with non-mowed corn (Fig. 7, left frame) shows that the impact of frost on the mowed corn will be minimal, whereas it is not clear whether the non-mowed corn will recover.