Frost on small emerged corn

Contributed by Robert Moloney, NK Brand Seeds

The last few nights have been downright chilly across the province.  Fortunately even though the temps have dipped below freezing and there has been widespread ground frost, the small emerged corn out there at this point should come through it OK.  We’ll likely lose some emerged leaves, but they’re not critical to the plant at this point.

With the low temperatures the last few nights we will definitely be seeing some leaves burned off.  These leaves aren’t critical to the plant long term, so this isn’t a huge concern.  The good news is that the growing point of the plant is still well insulated underground at this stage and as long as it is still alive the plant will likely be fine.  A bonus right now is that we good soil moisture which will help keep the soil temperatures warmer, even when air temperatures drop below zero.  To have a significant number of plants killed we would need to freeze the ground deep enough to kill the growing point or have frost penetrate a poorly closed seed slot and kill it.  With the good planting conditions this spring and current soil moisture this shouldn’t be much of an issue.

When assessing frosted corn you should wait for up to 48 hours to see what’s happening.  Although the damage is already done, it may take a day or two to show up.  Low lying fields and fields with a lot of trash are going to have the most injury.  Burnt off leaves can generally be ignored unless they are preventing emergence of new healthy leaves.  The important determinant of the plant health at this point is the health of the growing point of the plants.  Determining if the growing point is healthy is pretty simple.  First slice the plant in half vertically.  Then look at the inside of the plant near the base and make sure that the tissue there is white and firm.  That’s a healthy growing point.  If it is off colour, browned or watery then the growing point is likely injured and it would be a good idea to get a professional assessment.

2 other points: DO NOT spray anything on emerged corn for at least 3 to 4 days after frost/cold temperatures.  The plants are under stress and not as capable of metabolizing chemicals at this time.  BE CAREFUL STAGING PLANTS later in the season.  Since we are likely to lose at least a few leaves, the plant may be more mature than the number of leaves suggest.  If the first leaf you are counting doesn’t have a ROUNDED TIP you are missing at least one, but possibly more, leaves from the plant.  Although these leaves aren’t there anymore, they still count toward the staging for safe herbicide application.

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