I have noticed that there is a lot of sunscald on trees this year. Sunscald on trees usually happens on the south or south-west exposed bark where the sun’s warmth is stronger. The bark will die causing it to shed off the trunk or crack and peel vertically.
This causes the warm sun heating up the bark during the day in where the sap starts to become fluid. Then followed by cold night temperature causing the sap to freeze and burst. This process causes the bark to split and be damaged.
What trees on affected:
Certain species of trees have thinner bark including birch, maple, linden, boxelder (a maple), ash, and some evergreens are more susceptible to sunscald. Young bark, especially in fruit trees, are more susceptible than older bark which is thicker and provides better insulation for the cells. Trees that are well watered in the winter months are less likely to get sunscald.
How to prevent:
A number of products have been used to prevent sunscald. The old-time prevention was to use whitewash (white washable paint) to reflect sunlight keeping the bark cooler.
Wraps will also hold in some warmth at night, but this will have a very limited effect on the low temperature reached. Brown paper wraps actually absorb heat and can increase the temperature of the bark. Only white or silver products should be used.
Mulching with rock or organic material reduces sunscald injury. That is why trees in mulched beds show little if any sunscald. I have used plastic spiral wraps with holes (reducing temperature fluctuations and preventing rabbit damage. These should be removed each spring to reduce the potential insect and fungal problems listed above. As the bark ages and gets harder the wrap can be left off.
As for pruning a young tree, try to leave the first lower scaffold branch pointing to the south or south-west to shade that side of the trunk.
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