WIDESPREAD FROST HITS THE SW ONTARIO CORN CROP IN THE EARLY HOURS OF MONDAY MORNING MAY 10
Growers woke up Monday morning May 10 to frozen corn.Temperatures at sundown Sunday May 9 were approaching the freezing mark.By 3:00AM temperatures had dipped to -4.4C near the London airport. Recorded lows at the soil line reached -5.9C. By 6:00AM temperatures ranged from -2C in the Hamilton, Brantford and London area to -1C at Dresden Ridgetown and Chatham.By 10:00AM most emerged corn was taking on a limp darkened watery black-green appearanace much like that shown in the photo above.
Many factors are involved in how frost interacts with the crop.Planting depth,soil texture,residues, soil moisture reserves,topography and the geographical lay of the land can all have some degree of influence.Double click on the photo above to see more clearly how the two plants on the right are both frozen while the plant to the left is not.
Experience has taught us that the best way to diagnose frost injury is to give the crop an opportunity to respond to further growth.This means usually giving the crop 3-5 days before making any final assessments.Emerged to 2 leaf corn is more apt to bounce back favourably from an early season frost than corn that is in the 3 - 4 leaf stage.There are 2 reasons for this.First there is less dead plant tissue for the new emerging growth to push up through and secondly with 3-4 leaf corn the starch reserves of the seed have become pretty much exhausted.The first 4 leaves are in the seed and the endosperm starch of the kernel acts as the energy source to fuel the growth and development in the emergence of these first 4 leaves.If these leaves succcumb to frost the plants only reserves for initiating further growth are those in the mesocotyl.
New fresh green tissue rising up from the soil line like that shown in the above photo is ones surest indication that the plant is still alive and beginning to regrow.