Ash Rust - Puccinia sparganioides Ellis & Barth
Solomon, J.D.; Leininger, T.D.; Wilson, A.D.; Anderson, R.L.; Thompson, L.C.; McCracken, F.I. 1993. Ash pests: A guide to major insects, diseases, air pollution injury and chemical injury. Gen. Tech. Rep. SO-96. New Orleans, LA: U.S. Department of Agriculture, Forest Service, Southern Forest Experiment Station. 45 p.
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Importance. - Ash rust attacks most ash species growing east of the Rocky Mountains. It is most severe near coastal areas where its alternate hosts, cord and marsh grasses ( Spartina spp.), are abundant. Severe damage is infrequent since trees usually recover, although repeated infections have been reported to cause dieback and tree mortality.
Identifying the Disease. - From mid-April to mid-June, the upper surfaces of leaves develop yellow-orange spots, while chlorotic spots develop on petioles and current year twigs. Swelling of diseased tissues leads to distortion and necrosis of leaves, bending of petioles, and development of galls on twigs. Trees with severe infections appear scorched, and affected leaves often drop prematurely.
Identifying the Fungus. - Clusters of aecia containing orange-yellow aeciospores appear prominently on twigs, petioles, and lower surfaces of leaves. Yellow uredinia develop on alternate hosts and are replaced in the fall by dark-colored telia.
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Fruiting Bodies; distinctive pycnia and aecial "cluster cup" with orange-yellow aeciospores proliferating from the surface of infected tissue.
Edward L. Barnard, Florida DOACS |
Symptoms; Leaf distortion, petiole hypertrophy and distinctive pycnia and aecial "cluster cup" with orange-yellow aeciospores proliferating from the surface of infected tissue.
Edward L. Barnard, Florida DOACS |
Biology. - This fungus has five spore stages of which two must occur on alternate hosts for infection of ashes. In the spring, telio-spores that infect the current-year tissues of ashes, causing spermogonia and then aecia to develop. Aeciospores are blown to the infect alternate hosts on which uredinia develop in early summer. During the summer, urediniospores repeatedly infect cord or marsh grass. Uredinia eventually develop into brownish-black telia in the fall.
Control. - To control severe infections in valuable trees, fungicide sprays should be used at 2-week intervals in the spring starting at bud break.
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