Insects and Diseases of Trees in the South

by Anonymous

Fruiting on apple leaf the alternate host.

Cedar “apples” or galls are the characteristic signs of the fungus on cedars. Cedar needles are infected in the summer by wind-borne spores from apple leaves. By the next spring or early summer galls begin to appear as small greenish brown swellings on the upper needle surfaces. By fall, the infected needle turns into a chocolate brown gall covered with small circular depressions. The following spring, orange jelly-like tendrils protrude from the galls producing an attractive ornament for the cedar tree. Spores produced from these orange spore masses are then capable of reinfecting apple leaves, thus completing the fungus life cycle.

No practical control of the rust on cedars is available because of the low value of cedar. However, considerable effort is expended to protect apple trees. Where apple is to be protected, cedars should be eliminated in the vicinity or, rust galls should be picked or cut off cedars before the galls mature.

CEDAR BLIGHT

Cedar blight, caused by Phomopsis juniperovora, is most severe on eastern red and Rocky Mountain cedars. Other hosts include arborvitae, cypress, and Atlantic white cedar. The disease ranges from the mid-West to the Atlantic coast and south to Alabama where it is most common in nurseries.

Needle symptoms on 1-0 eastern red cedar nursery stock and 5 year old Arizona cypress.

Symptoms on red cedar resemble that of drought. The tips of branches are killed back and sometimes entire trees will turn brown. The fungus forms black fruiting bodies on needles and stem lesions. Fungus spores are distributed by rainwater; nursery overhead sprinkling systems also facilitate blight spread.

Control of cedar blight is initiated by removing and burning infected nursery stock early in the season before infection becomes heavy. Seedbeds should be well drained. Avoid introducing cedar stock to an infected nursery. The location of cedars in the nursery should be changed frequently and, where possible, cedar beds should be kept well away from older cedar or cedar hedges. Seedlings growing in low-density seed beds are more vulnerable to the blight; thus beds should be fully stocked. Cedar mulch should never be used on cedar beds. Avoid wounding nursery transplants. No economically feasible control is available for forest stands.