ANR-1196, New March 2001. Austin Hagan, Extension Plant Pathologist, Professor, Entomology and Plant Pathology, Auburn University

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Plant Disease Notes Cercospora Needle Blight on Leyland Cypress

Cercospora needle blight is a common and occasionally damaging disease on Rocky Mountain juniper and Eastern red cedar, as well as on bald and Arizona cypress. Recently, nurseries and Christmas tree plantations in Alabama have reported damaging outbreaks of Cercospora needle blight on Leyland cypress. In field plantings, this disease tends to cause more damage to stressed trees or trees in otherwise poor condition.

Symptoms

Browning or blighting of the scales or needles, which typically starts on the inner portions of the lower branches near the base of the tree, progresses upward and outward toward the shoot tips. At advanced stages of this disease, all scales except the current year's growth die. Selected, highly susceptible trees may succumb to this disease. Typically, symptoms usually appear during the summer months.

Disease Cycle

Eastern red cedar and other native tree hosts are most likely the source of the causal fungus Cercospora sequoia. The fungus may be introduced into landscape plantings on disease B & B or container-grown nursery stock. The fungus overwinters in the needles and other host tissues. Spores of the causal fungus, produced during periods of wet weather in the spring and fall, are spread by air currents and wind-driven rain to healthy trees. Free water is needed for spore germination and successful infection of host foliage.

Control

In nurseries, protective fungicide sprays should provide good protection from Cercospora needle blight. For best results, begin sprays in mid- to late spring before fresh symptoms appear. Referring to the intervals listed in the following table, repeat preventative sprays on Leyland cypress throughout the summer until the cooler, drier weather in October.

Thorough coverage of the foliage is critical to the control of Cercospora needle blight. When spraying, be sure to use enough pressure to force the fungicide through the canopy to thoroughly wet the innermost shoots, especially those near the base of the plant. Fungicides cleared for the control of Cercospora leaf spot are listed in the following table. Note: the information concerning efficacy of fungicides for the control of Cercospora needle blight dates back to the late 1950s and 1960s. No recent efficacy trials have been conducted with any registered fungicides.

Fungicide	Application Rate		Comments
	Per Gallon	Per 100 Gallons
azoxystrobin Heritage 50W	-	1 to 4 ounces	Apply at first sign of disease and repeat every 14 to 28 days.
propiconazole Banner Maxx	-	8 to 12 fluid ounces	Apply every 30 days when conditions favor disease.
thiophanate-methyl 333650W 3336 4.5	1-1/2 to 2 t. 1 T.	12 to 16 ounces 10 to 20 fluid ounces	Spray at 7- to 10-day intervals during humid, wet summer weather. Apply to drip. Use surfactant to improve coverage with wettable powdery formulations. Note: other formulations of the thiophanate-methyl are available and are also labeled for the control of this disease.
thiophanate-methyl Zyban 79W	5 t.	3 lb.
t. = teaspoon T. = tablespoon

Use chemicals only according to the directions on the label. Follow all directions, precautions, and restrictions that are listed.

The pesticide rates in this publication are recommended only if they are registered with the Environmental Protection Agency and the Alabama Department of Agriculture and Industries. If a registration is changed or canceled, the rate listed here is no longer recommended. Before you apply any pesticide, check with your county Extension agent for the latest information.

Trade names are used only to give specific information. The Alabama Cooperative Extension System does not endorse or guarantee any product and does not recommend one product instead of another that might be similar.