Ask Mr. Smarty Plants

Cercis canadensis (eastern redbud) is a native of North America and is found naturally in Kansas, so we can't blame this problem on the tree being a non-native. It does appear that your tree is a victim of the fungus Botryosphaeria which can cause cankers on branches and stems of trees and shrubs with low vitality. The redbud naturally has "growth cracks" in its structure. When the plant has been weakened by possibly bad environmental problems, such as winter damage, prolonged dry periods, root problems and physical wounds, plants can be weakened and that facilitates opportunistic infections by the canker. Please check this University of Massachusetts Extension website to see the pictures and descriptions of infected trees, to determine if the problem is the same.

Some of the management strategies suggested in this article include intervening to minimize environmental and cultural stress on the trees. A tree with good vitality will respond on its own to inhibit the spread of the fungus. Water the tree when it is dry, fertilize, maintain a good compost layer over the root zone, and avoid damage to the tree. Remove the infected branches when the weather is too cold and dry for the fungus to infect the pruning wounds, and dispose of the infected branches away from the trees.

Cercis canadensis