Sunscald is caused by rapid fluctuations in temperatures causing bark tissues to die and damaging the fruit. It typically develops on the south or southwest side of the tree or on fruit that is suddenly exposed to direct sun. There are two categories of sunscald by season-summer and winter.
For region-specific information, please contact your local Giving Grove partner. If you would like more information like this sent straight to your inbox, consider subscribing to The Serving, The Giving Grove’s quarterly newsletter.
Causes:
Both seasons of sunscald are cased by rapid fluctuations in temperatures.
Summer sunscald occurs from lethal high temperatures from sun exposure. It is more common in southern states.
Winter sunscald occurs when frozen bark tissue thaws and rapidly refreezes, causing damage to the tree.
Appearance:
Trunks and/or branches: Damage is typically found on south or southwest side of the tree. Elongated area of dead bark on lower section of tree. Area may be sunken with dried, cracked bark that peels off and exposes dead wood. Young trees, trees with thin bark, and newly planted trees are more susceptible to sunscald.
Fruit: Damaged fruit develop irregular reddish-brown patches that are sunken below the surface of the fruit. Fruit flesh may also be damaged under the skin.
How to Treat:
Provide winter protection with white tree spirals (when trees are young), and/or paint older tree trunks with a mixture of 1 part water to 1 part interior latex white paint. This helps eliminate bark splitting in winter due to sun scald.
It is difficult to detect early symptoms so preventative care is very important:
Use proper irrigation, especially during the hot and dry parts of summer
Mulch around the base of the tree
Resources: Patrick L. Byers, Horticulture Specialist, Washington State University Extension, University of Arkansas-Agriculture Division, Deep Green Permaculture, and K-State Research & Extension.