Maples are probably the most common victim, but any young thin-barked tree is susceptible to late winter sunscald. To prevent damage from the disease, use commercial tree wrap, polypropylene tree protection tubes or white latex paint to protect tree trunks.
Sunscald occurs when warm sunshine heats a tree's bark and warms it enough to make that part of the tree think spring has arrived. The disease is most prevalent on the southwest side of trees because the late afternoon sun typically warms the tree the most. Cells become active from the warmth but freeze when the sun sets and temperatures drop.
The southwest side of a tree exposed to sun can be a full 40 degrees warmer than the tree's shaded side, according to a research study in Georgia.
Damage from sunscald often goes unnoticed until weeks or months after it actually happens. Affected tissue discolors and sometimes looks flattened or sunken before cracking and sloughing off the tree. Scar tissue may form around the edge that will eventually grow over the damaged area.
Tissue damaged by sunscald is also more susceptible to disease. The wound is an easy entry point for disease-causing fungi. If the tree becomes stressed from the damage, it will also be more attractive to insect pests.
Protect the tree from the ground to the lowest branches. If using protection tubes, more than one tube may be necessary to adequately cover the trunk. White latex paint works by reflecting the sun and only needs to be applied on the southwest side of the trunk if being used. The paint will fade away over time.
Commercial tree wrap and/or protection tubes are available at many garden centers.
Remove tree wrap and protection tubes after the last hard freeze in the spring. If left on, they can become hiding places for insect pests.
Trees that suffer from sunscald injury should be watered over extended dry periods to reduce stress. Mulching properly, with large rings over the root zone and mulch material pulled away from the base of the tree also helps to reduce tree stress.
- Jennifer Smith is the Douglas County Extension Agent - Horticulture for K-State Research and Extension and can be reached at 843-7058.