Damage to a Dawn Redwood Tree

Redwood Canker

• The chief causal agent of damage to a dawn redwood tree is typically a disease known as canker. This ailment in most species of redwood is brought on by three separate pathogens; Botryospheria dothedia, Seridium and Cytospora. Canker is especially prevalent in dawn redwoods planted outside of their ideal growing range or in areas unsuited for them culturally. The fungi rarely attack healthy redwoods that are otherwise not environmentally stressed.

Infection Process

• Canker in a dawn redwood is spread by fungal fruiting bodies that live in the dead tissue of infected trees. Although it can be disseminated throughout the year, most infection occurs during the rainy season as rain splash transfers the fungus throughout trees and to adjacent specimens. Wounds in the tree, cracks in the bark and sunburned tissue are the primary entry points for canker fungi. As the disease spreads, dieback of twigs and branches occurs.

Damage

• In severe cases, as much as one-third of the crown of a dawn redwood may be killed by canker. Previous to extensive dieback, cankers will display as depressed, dark areas in the bark surrounded by a circle of raised wound tissue. Should the bark be peeled back from a canker, the wood below would appear discolored. Small branches are quickly killed by canker as the disease girdles -- strangles -- the branch and deprives it of water and nutrition.

Management

• The best way to prevent canker damage to a dawn redwood tree is to ensure the health of the specimen. It should be planted only in its native range and provided significant summer water and proper irrigation: redwoods do not appreciate overly wet soil. Avoiding mechanical injury to the tree and the prompt removal of canker-infected tissue is vital to preventing further transmission of the disease. There is no chemical control available for redwood canker.