• Topics: Smith, Jason A | Leyland Cypress | Urban Tree Pest Management

Seiridium Canker of Leyland Cypress¹

Overview

Seiridium canker, also known as Cypress canker, was first reported in California in the late 1920s and has since spread throughout North America and into Florida wherever Cupressaceae (cypress family) grow. The disease has raised some concern in Florida due to the damage and mortality observed on Leyland cypress. Leyland cypress can be killed or severely disfigured by the disease. Disease management considerations and tree replacements with resistance to Seiridium canker are recommended.

Causal Agent

Seiridium canker can be caused by one of three different fungal species: Seiridium cardinale, S. cupressi and S. unicorne (Barnes et al., 2001). In the United States, Seiridium canker is caused by S. cardinale (the most damaging of the three fungal species), which is found in California (Barnard and Leahy, 2004; Sinclair, 2005, Tisserat et al., 1991; Wagener, 1928 and 1939), S. unicorne which is found in the south central and southeastern states, (Sinclair, 2005) and S. cupressi, which is most common in Florida on Leyland cypress (Barnard and Leahy, 2004; Sinclair, 2005). All three species produce asexual fruiting bodies (pycnidia) in cankers and in S. cardinale, also in cone scales (Sinclair, 2005).

Host Range

Seiridium canker has been found on a wide range of host species in the Cupressaceae (cypress family), with susceptibility depending on geographical location, host species and the local fungal strain(s) present (Madar et al, 1989; Sandrock et al., 1999; Tisserat, 1991). Worldwide, the disease has been most damaging to Mediterranean cypress (Cupressus sempervirens) and Monterrey cypress (Cupressus macrocarpa) (Graniti, 1993 and 1998; Strouts, 1973). Several tree genera have been reported as hosts including: Chamaecyparis, Cupressus, Cryptomeria, Juniperus, Libocedrus, Platycladus, Taxodium, Thuja, and the intergeneric hybrid genus X Cuprocyparis (Barnard and Leahy, 2004; Sinclair, 2005). In the southeastern United States , the disease rarely affects native tree species such as eastern red cedar (Juniperus silicicola) and Atlantic white cedar (Chamaecyparis thyoides), but is common on cultivated Leyland cypress (X Cuprocyparis leylandii) (Barnard and Leahy, 2004).

Symptoms and Signs

The symptoms of Seiridium canker most often appear as "flag" branches where individual branches fade from green to yellow to reddish-brown due to girdling cankers (Figure 1). Infection may affect a single branch or multiple branches throughout the tree and mortality of the entire tree is common. Closer examination reveals oval cankers (Figure 2) that are sunken and often reddish with resin exuding from the margins, especially on new, rapidly expanding cankers (Barnard and Leahy, 2004; Sinclair, 2005; Windham et al., 1999).

The fruiting bodies (pycnidia) are the only sign observed, are black and appear as small pustules (blisters) (0.3–15 mm in size) that break through the bark during wet weather that open to release the spores (conidia) (Barnard and Leahy, 2004; Sinclair, 2005).

Figure 1. 

Symptomatic flag branch on Leyland cypress typical of Seiridium canker.

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Figure 2. 

Lens-shaped canker typical of Seiridium canker (Photo Credit: Jason Smith)

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Figure 3. 

Arizona cypress (left) and southern red cedar (right), two canker-resistant alternatives to Leyland cypress in the south.

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Disease Cycle

Wounds made by insects, hail or mechanical injury are often where infection begins on the tree. In addition, drought stress predisposes Leyland cypress to infection by the fungus (Madar et al., 1989; Sinclair, 2005). The fungus overwinters in colonized bark and old cankers during winter and dry weather. The fruiting bodies and spores are produced during wet weather (Sinclair, 2005).

While spore release and branch infections take place during wet weather, disease development and symptom expression (dying branches) are greatest in areas with high temperatures and dry conditions in summer.

Management

Disease management options for Seiridium canker are limited. Although individual high-value trees may be protected by fungicides (McCain, 1984) and pruning out individual infected branches might prolong survival of susceptible trees, planting either resistant species or varieties is the only realistic option for long-term disease control (Santini and Donardo, 2009; Xenopoulos, 1990). In Florida, Leyland cypress has been widely promoted and planted in ornamental settings when other species are better adapted. Leyland cypress is a hybrid between two Pacific coast species that are native to cool climates and unsuited to Florida's hot and dry seasons. This leads to drought stress for trees on many sites in Florida and predisposition to Seiridium spp. as well as other fungal and insect pests (Barnard and Leahy, 2004).

Conifer species better adapted to Florida growing conditions, less likely to be drought-stressed, and with resistance to Seiridium spp appear in Table 1. Two native tree species, southern red cedar (Juniperus silicicola) and Atlantic white cedar (Chamaecyparis thyoides) are well adapted to Florida conditions (if local seed origins are used) and possess qualities similar to those of Leyland cypress. These qualities include fast growth, easy propagation, dense pyramidal shape and good drought tolerance once the tree is established. A few exotic species are worth trying in Florida and have previously performed well in the region. Plant several species and cultivars to maintain diversity in the landscape and prevent disease outbreaks in the future (see figure 3).

References

Barnard, E. L. and R. A. Leahy. 2004. Cypress canker in Florida. Florida Department of Agricultural and Consumer Services. Plant Pathology Circular 404. 4 pp.

Barnes, I., J. Roux, M. J. Wingfield, M. P. A. Coetzee, and B. D. Wingfield. 2001.Characterization of Seiridium spp. associated with cypress canker based on β-tubulin and histone sequences. Plant Disease 85: 317–321.

Graniti, A. 1993. Seiridium blight of cypress – another ecological disaster? Plant Disease 77: 44

________. 1998. Cypress canker: a pandemic in progress. Annual Review of Phytopathology 36: 91–114.

McCain, A. H. 1984. Cypress canker control with fungicides. Journal of Arboriculture 10:213–214.

Madar, Z., M. Solel and M. Kimchi. 1989. Effect of water stress in cypress on the development of cankers caused by Diplodia pinea f. sp. cupressi and Seiridium cardinale. Plant Disease 73: 484–486.

Sandrock, D. R., J. L. Williams-Woodard, and M. A. Dirr. 1999. Susceptibility of Atlantic white cedar cultivars to Botryosphaeria and Seiridium cankers. SNA Research Conference 44: 204–207.

Santini, A. and V. Donardo. 2009. Genetic variability of the 'bark canker resistance' character in several natural provenances of Cupressus sempervirens. Forest Pathology 30: 87–96.

Sinclair, W. A., H. H. Lyon, and W. T. Johnson. 2005. Diseases of trees and shrubs, 2nd Edition. Cornell University Press, Ithaca, New York. 574 p.

Strouts, R. E. 1973. Canker of cypress caused by Coryneum cardinale Wag. in Britain. European Journal of Forest Pathology 3: 13–24.

Tisserat N. A., A. Nus, and L. W. Barnes. 1991. A canker disease of the Cupressaceae in Kansas and Texas caused by Seiridium unicorne. Plant Disease 75: 138–140.

Wagener, W. W. 1928. Coryneum canker of cypress. Science 67: 584.

_____________ 1939. The canker of Cupressus induced by Coryneum cardinale N. SP. Journal of Agricultural Research 58: 1–46.

Windham, A. S., T. C. Stebbins, and M. T. Windham 1999. Canker and shoot blight diseases of Leyland cypress. Proceedings of the Southern Nurserymans' Association Research Conference 41: 178–179.

Xenopoulos, S.G. 1990. Screening for resistance to cypress canker (Seiridium cardinale) in three Greek provenances of Cupressus sempervirens. Forest Pathology 20: 140–147.

Tables

The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other extension publications, contact your county Cooperative Extension service.

U.S. Department of Agriculture, Cooperative Extension Service, University of Florida, IFAS, Florida A. & M. University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Nick T. Place, Dean.

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