Plant Health Problems

Diseases caused by Fungi:

Nursery blight, Phomopsis juniperovera.
This tip dieback occurs occasionally on white cedar but is much more common and serious on red cedar. A small canker girdles the twig, which dies.

Control can be achieved by pruning affected twigs. Use of fungicides is not usually necessary although if warranted, they should be applied before symptoms are severe. Among compounds registered for use in Connecticut are chlorothalonil and thiophanate-methyl. Consult the label for dosage rates and safety precautions. Copper-containing compounds should be avoided, due to the risk of severe discoloration of the foliage for several seasons following application. Affected twigs should be cut and disposed of.

Witches'-broom, Gymnosporangium ellisii.
Witches' brooms appear at the ends of branches; on young trees the entire top may be broomed. Branches beyond the infection point usually die as soon as the fungus girdles the branch. Cross-sections of infected wood show wedge-shaped brown spots in the wood. In the spring, brown telial horns grow out of the infected area and produce spores that infect the bayberry and sweet fern, which in turn produce spores to reinfect the white cedar.

The only control known is the eradication of the bayberry and sweet fern.

Gall rust, Gymnosporangium biseptatum.
Good-sized, spindle-shaped galls appear as a result of infection by this fungus. The branch beyond the gall usually dies. This fungus requires an alternate host, the serviceberry, in order to complete its life cycle and initiate new infections. However, once the fungus invades the cedar wood, it becomes perennial in the tree.

Once infection occurs, controls are not effective.

Diseases caused by Physiological/Environmental Factors:

Foliage browning.
All the "leaves" on the inside of the tree turn reddish-brown and fall readily to the ground either in spring or fall. This natural shedding occurs often after a dry season or may happen every second or third year varying with the individual tree and conditions. The discoloration is distinguished from fertilizer burn by being on the inside of the entire tree whereas fertilizer burn or sunburn due to root injury starts at the tip of the branch, working its way back, and generally progresses up the tree from the lowest branches. Red spider mite injury differs in that a bronzing usually of all the leaves on a branch or the entire tree may "suddenly" appear during the summer. Winter bronzing is due to physiological changes and is tied in some way with the nutrition of the plant as yet not understood. Winter bronzing disappears with the advent of warm weather.

Insect Problems:

See Arborvitae, Calidiellum rufipenne.