This fungal disease affects many woody plant species. Hosts include citrus, mulberry, and walnut.
Identification
The fungus causes bark cracking and cankers. On infected limbs, leaves suddenly wither, turn brown, dry up, and die. Dead leaves typically remain attached to the twigs.
Damaged bark may peel off or remain tightly attached to dead limbs. Cracked bark can bleed profusely and contain viscous or dried gum. Removing affected bark often reveals black, powdery growth underneath, so this disease is called sooty canker. This dark discoloration occurs under the cambium layer (inner bark) but extends only shallowly into the wood.
There are many other common causes of cankers, including other species of canker fungi.
Life cycle
The Neofusicoccum fungus is a relatively weak pathogen. It usually infects trees through wounds caused by freezing, fertilizer burn, sunburn, or mechanical injury, such as from pruning.
Spores of Neofusicoccum are produced in tree litter and on dead leaves, twigs, and branches in the tree canopy. These spores are spread by splashing water and air movement. Spores cause infection when they contact wounded host tissue.
Solutions
Protect trees from injuries. Properly prune off all diseased branches each year. Provide trees good cultural care and a proper growing environment; severe damage is more likely on trees that are water stressed. Provide adequate soil moisture by irrigating appropriately throughout the growing season.
