The ISU Plant Disease Clinic routinely receives samples of leaves that show damage caused by something other than an infectious agent. A damaging freeze happened the night of April 8th. Cells of developing buds may have been injured. If cells were killed, leaves and flowers might grow out in a deformed manner. The edges will look tattered, or there may be holes of various sizes in leaves, usually between veins. These damaged areas usually have a green edge. Damage caused by insect feeding or fungal infection typically causes the leaf margin or edge to turn a darker color. Not all leaves on a tree will have this appearance. When an injurious cold event happens, only cells in a sensitive state will be affected. Leaves that form later should be normal. One or a few species may be affected because the timing of developmental stages varies between plant species.
This article originally appeared in the 5/2/2003 issue.