Cercospora Blight Diagnostic Guide
Cercospora sequoiae is a new disease to Leyland cypress trees. Cercospora has commonly infected junipers, cedar and arborvitae, causing unsightly needle browning in the lower portion of the plant. In severe cases only the needles on the upper tips or very outside of the plant remain green. It is not uncommon, especially on Leyland cypress for Cercospora to kill the plant entirely.
Rocky Mountain juniper, eastern red cedar, bald cypress, Arizona cypress and Leyland cypress. Cryptomeria may also be a host.
Eastern Red Cedar
Rocky Mountain Juniper
Signs of Damage
- Browning of inner, lower portions of the tree beginning in the late spring to summer.
- Symptoms progress upward and outward throughout the season; at epidemic level only the current year’s leaves survive.
- Fruiting bodies appear as tiny greenish pustules on the upper surface of needles or small twigs.
- Spores are released during wet weather in the spring and fall and are spread by air currents and wind driven rain.
- New infections occur when spores land on a film of water covering a suitable host.
Prevention is the best strategy for managing Cercospora blight. Some combination of cultural practices and protective fungicide sprays will be most effective. Cultural practices include watering without wetting foliage during drought conditions, providing proper nutrition via fertilization, and mulching to retain soil moisture. Fungicide sprays can protect newly emerging foliage. Treatments should be applied as new leaves are emerging. In wet climates or during moist springs reapplications will be necessary at 14-21 day intervals until conditions dry out.
A Diagnostic Guide is designed to help you identify a pest issue and management solutions. Always refer to product label for all rates and approved uses. Some images courtesy forestryimages.org. Use of the images does not imply endorsement of treatments by forestryimages.org