Passalora Needle Blight
By: Aaron Martin
Passalora needle blight, often referred to a cercospora and cercosporidium needle blight, a common disease on Leyland cyperus and other coniferous species of Juniperus, Thuja, Cupressus, Taxodium, Cryptomeria, and Sequoia. It has been become a prevalent disease in landscapes and nurseries, and can cause significant problems for both landscape companies and ornamental growers.
The disease is caused by the pathogen Passalora sequoiae. Native trees such as eastern redcedars are believed to be the original disease host. The pathogen overwinters in the needles of the plant. Spores from the disease are produced in the spring and fall during periods of wet weather, and are spread by wind and water. Moisture is necessary for the spores to germinate and infect the host plant. Symptoms appear during the summer months as blighting of previous years’ growth in the lower and inner portions of the plant, moving outward and upward to the top of the plant. New growth near the top of the plant may also be infected under severe disease pressure.
Cultural practices to prevent this disease include planting with adequate spacing to allow for proper airflow. Watering strategies should aim to reduce moisture in the canopy and prevent the spread of spores. This includes the use of drip irrigation or restricting overhead irrigation to pre-dawn hours. Prune out diseased limbs and disinfect pruning equipment to prevent spreading spores.
Few fungicides are not labeled for passalora needle blight however several fungicides have been suggested here and also here. Fungicide applications should begin in the early spring and continue until cooler and drier air in the fall. Adequate needle coverage is extremely important for satisfactory control of this disease. Spray needles until runoff with enough volume and pressure to reach the inner most portions of the plant, particularly at the base of the tree where initial infection usually occurs. Consider adding a good quality surfactant to help achieve optimum coverage.
References
Hagan, A. 2004. Cercospora needle blight on Leyland cypress. Alabama Cooperative Extension Bulletin ANR-1196. http://www.aces.edu/pubs/docs/A/ANR-1196/ANR-1196.pdf
Scott, J.M., et al. 2010. Leyland cypress diseases, insects and related pests. Home and Garden Information Center. Clemson Cooperative Extension Bulletin HGIC 2004. http://www.clemson.edu/extension/hgic/pests/pdf/hgic2004.pdf
U.S. Forestry Service. 2011. Cercospora blight of junipers. http://www.fs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb5347863.pdf