The Bark Is Breaking on the Apple Tree: What Do I Do About This Problem?

Causes

• Bark splitting can be the result of numerous factors, including sudden fluctuations in temperature in which severe cold snaps late in winter or early spring freezes are followed by rapid thawing. This leads to a condition called frost cracks. Fluctuations in growth pattern also split bark when dry weather suddenly is followed by moist and ideal growing conditions, causing sudden growth of tree that can split the bark. Using a high-nitrogen fertilizer during fall and sunscald also makes tree bark prone to splitting.

Avoiding Sunscald

• Sunscald damage often is seen on young trees during the winter. Signs of the damage are not noticed until the following summer when the bark splits and peels from affected sites. To reduce chances of sunscald, do not excessively prune trees with dense canopies. Manage tree growth by pruning limbs gradually over the years. Use a tree wrap around the trunks of new plantings to protect them from damage.

Fertilizer Timing

• Avoid fertilizing trees late in their growing season. This leads to growth spurts during the cold season and makes tender, new growth prone to winter injuries such as bark splitting. Fertilize a tree no later than in the fall, immediately after leaf drop and when the tree is dormant. Keep trees well-irrigated during hot, dry weather.

Frost Protection

• Prevent frost cracks on trees, also referred to as southwest injury because it occurs on the southwest side of the trunk, by painting the trunk white or using a tree wrap. Frost cracks often start from a tree wound, with damage initiating inside the tree, and eventually cause the outer bark to split open. The best way to minimize frost cracks is to avoid excessive use of nitrogen, as this can combine with sudden warm fall temperature and high humidity and lead to bark splitting.

Management

• Once the bark has split, avoid any attempts to seal the wound with tar or paint, as this will not be effective, according to the Cornell University Plant Disease Diagnostic Clinic website. Instead, the website recommends tracing around the split area on the bark with a sharp knife, digging into the bark ½ to 1 inch back from the borders of the split area. Sterilize the knife between cuts by dipping it in a solution of one part bleach and 10 parts water. Remove the bark from inside the cut area. This will help a healthy tree to produce callus. Bark splits usually close on their own over time, leaving only a ridge in the trunk.