Landscape and Nursery - Daylily Leaf Streak

The following is information on Daylily Leaf Streak, a diseas of daylilies that we see in Delaware.

Daylily Leaf Streak

Brown rectangular spots and yellow streaking on the leaves are symptoms of daylily leaf streak, caused by the fungus Aureobasidium microstictum. Cultivars vary in susceptibility to this disease - in extreme cases on highly susceptible cultivars, virtually all of the foliage can be affected. The pathogen overwinters on infected leaves, and is spread by splashing water from overhead irrigation or rainfall. Infection is limited when temperatures reach 90 °F or above.

Control: Fungicides effective in protecting uninfected leaves from this disease include thiophanate methyl (Cleary's 3336 and others), chlorothalonil (Daconil), and azoxystrobin (Heritage). For maximum effectiveness, fungicides should be applied starting when new growth is emerging.

Daylily leaf streak. Photo from the Fla. Dept. Agric. & Consumer Services, Division of Plant Industry.

Information from the Greenhouse May 1, 2009 edition of the TPM/IPM Bi-Weekly Report from the University of Maryland Cooperative Extension Central Maryland Research and Education Center http://www.ipmnet.umd.edu/09May01G.pdf