Improper pruning when this ash tree was young caused it to develop included bark and poor limb structure. This tree may be hazardous and pose a risk of limb failure (drop).

Main branch crotch of possibly hazardous ash improperly pruned when young resulting in occluded bark and poor limb structure. Modesto by JKC   Credit: Jack Kelly Clark, UC IPM
Credit: Jack Kelly Clark, UC IPM