~~ To prevent sunscald / sunburn. Too much hot sun shining onto a tree trunk every day will cause damage to the bark over time. Painting the tree trunk can prevent sun damage.
~~ To protect trunks if a larger tree is removed and no longer provides shade to a smaller tree, or if a large number of tree branches are cut off and the tree trunk is no longer shaded. Only the lower trunks are painted because the upper portion of the tree is protected by the foliage.
~~ To prevent the bark of a tree from splitting and cracking off. This can happen in colder climates when there are freezing temperatures at night followed by a daytime thawing. The painted white trunk helps reflect sunlight during the day and keeps the tree warmer at night.
~~ To protect the bark of the tree from infestation by borer insects. These insects often attack trees with the weakest outer protection. Paint the entire trunk, including dormant buds, and paint the trunk 2 inches below ground in case the soil settles. The trunk of a potted tree should also be painted.
~~ To protect exposed limb stumps after cutting. The exposed areas can sunburn easily and also allow entry for insects and diseases.
~~ To help repel adult beetles and weevils, especially on young trees. Sun reflection off the paint should reduce insect movement across the painted zone.
What to Use to Paint Tree Trunks:
Make a mixture of 50% latex indoor paint or lime, and 50% water. You do not need to use white paint; any light-colored paint will work. Look at the label to make sure there are no additives.
Or you can mix one-third white paint, one-third drywell joint compound, and one-third water, which makes a thicker mixture.
Use a paint brush rather than a sprayer, and one coat is usually enough unless you live in a place with extreme temperatures.
Never use an oil based paint or exterior paint because these type of paints can harm the tree.
If you don't care for the look of white tree trunks, you can buy tree wrap or burlap.