Introduction Seiridium cardinale (Wagener) Sutton et Gibson has been wrecking havoc on populations of cypress (particularly Cupressus macrocarpa and C. sempervirens) since its discovery in California in 1927 and its spread to Europe shortly thereafter (Raddi and Panconesi 1981; Wagener 1928). In the 1920’s, disease symptoms in C. macrocarpa were originally attributed to insects (Wagener 1928). Wagener officially identified the causal agent as Coryneum cardinale in 1939, though Sutton and Gibson later renamed the fungus to its current taxonomical standing. The causal agent of cypress canker has now been identified as three phenotypically similar, yet genetically distinct Seiridium species (Barnes et al. 2001; Graniti 1998; Tsopelas et…show more content… 2001). Of the three, S. cardinale is the most pathogenic, producing the most seiridins (fungal metabolites that are toxic to trees), and is most commonly associated with cypress canker in the literature (for this reason I will focus on S. cardinale during the remainder of this review) (Graniti 1998).
S. cardinale is an imperfect, thermophilic Ascomycete, forming irregular, scattered or clustered, blackish pustules (acervuli) that can be partially immersed or erumpent on the dead bark of cankers on cypress twigs, branches, and stems (Graniti 1998; Raddi and Panconesi 1981; Wagener 1928, 1939). Oblong-fuscid and septate conidia are borne on simple or branched conidiophores and are readily dispersed by rain, wind, insects, and birds under conducive climatic conditions (high relative humidity with alternating periods of hot and humid with dry and windy) during the spring and autumn (Graniti 1998; Raddi and Panconesi 1981; Wagener 1939; Zocca et al. 2008). The pathogen can remain dormant, without losing pathogenicity, during non-conducive conditions within the outer bark as mycelium or chlamidospores (Graniti 1998; Raddi and Panconesi 1981).
Symptomology The first and most notable symptom of infection on susceptible cypress occurs as irregular patches of crown chlorosis and death, particularly on small and young branches (Granti 1998; Raddi and Panconesi 1981; Wagener 1928, 1939). Closer examination of symptomatic trees reveals the presence of tapering,