SEIRIDIUM CANKER of LEYLAND CYPRESS Dr

FACT SHEET

SEIRIDIUM CANKER OF LEYLAND CYPRESS Dr. Yonghao Li Department of Plant Pathology and Ecology The Connecticut Agricultural Experiment Station

Leyland cypress (× Cupressocyparis even the trunk. The first evidence of leylandii) is a fast-growing conifer that has Seiridium canker is a browning or a been widely grown to form hedges, reddening of the surface of stems. This is windbreaks, and barriers in commercial and followed by the development of sunken, residential landscapes. Unfortunately, dark-brown cankers that may girdle the Leyland cypress is very susceptible to a small branches and cause dieback (Figure fungal disease called Seiridium canker-- the 1). Seiridium cankers are often thinly increased popularity of planting this conifer elongated and show dark-brown to purplish in the landscape has led to substantial discolorations of stem tissues. Exuding increases in the incidence of this disease. resin may also be observed on the surface of Seiridium canker can cause branch dieback, infected areas (Figure 2). Small, black damage to the main trunk, and may fungal fruiting bodies may be visible on eventually kill the tree. Physical injuries, symptomatic tissues (Figure 3). If the such as drought stress and winter damage, pathogen grows into the main trunk and can result in Leyland cypress trees becoming forms cankers, the entire tree can be killed. more vulnerable to the disease. DISEASE DEVELOPMENT SYMPTOMS AND DIAGNOSTICS Three Seiridium species, S. cardinal, S. The pathogen can infect stems, limbs, and cupressi, and S. unicorne, are associated

Figure 1. Browning of needles above the dark- Figure 2. Resin oozing from the infected area brown canker lesion on the stem. and discoloration of cambium tissues.

Seiridium Canker of Leyland Cypress Y. Li The Connecticut Agricultural Experiment Station (www.ct.gov/caes) 1

MANAGEMENT Alternative tree species: In areas where Seiridium canker has been a problem, resistant tree species such as Thuja ‘Green Giant’ and T. occidentalis ‘Smaragd’ should be selected for replacement of screens and hedges. Design landscapes using different tree species and cultivars to maintain genetic diversity and to prevent disease outbreaks.

Cultural practices: Plant Leyland cypress in well-drained soil. Maintain tree vigor by Figure 3. Spores (conidia) released from black watering trees during periods of heat and fungal fruiting bodies (pycnidia). drought. Avoid overhead irrigation to reduce the risk of disease spread. Space plants with Seiridium canker diseases. They have adequately to improve air circulation and to wide host ranges that include many species prevent rubbing between branches. Scout for in the genera Chamaecyparis, Cryptomeria, the disease and correctly identify the Cupressus, Juniperus, Libocedrus, pathogen, which is important for effective Platycladus, Taxodium, and Thuja. The disease management. When the disease is pathogens can survive in infected branches found, prune infected branches about 3 to 4 and trunks for many years. When inches below the cankered area. Disinfect environmental conditions are moist and wet pruning tools with either 10% household during the growing season, spores (conidia) bleach or 70% alcohol. Severely affected are released from fungal fruiting bodies trees should be removed from the area. (pycnidia). These spores are locally dispersed by splashing water from rain and Fungicide application: Currently, fungicides overhead irrigation. The pathogen also can are not effective for controlling this disease. be spread by contaminated pruning tools, movement of infected plant materials, and February 2015 insects. The pathogens infect stem tissues through wounds that are caused by winter Dr. Yonghao Li damage, insects, or other mechanical The Connecticut Agricultural Experiment injuries. The optimal temperature for disease Station development is 77F. During the hottest Department of Plant Pathology and Ecology months of the year, growth of S. cardinal in 123 Huntington Street, P.O. Box 1106 host tissues is slow or even arrested. Plants New Haven, CT 06504 that are stressed by drought and freeze damage are particularly vulnerable to the E-mail: [email protected] disease. Severe damage is most likely on Phone: (203) 974-8601 sites with dry weather and high daytime Website: www.ct.gov/caes temperatures, although wet conditions are required for spore dispersal and infection.

Seiridium Canker of Leyland Cypress Y. Li 2 The Connecticut Agricultural Experiment Station (www.ct.gov/caes)