Berry-Smith (1962) and Dingley (1965) recorded this fungus from New Zealand as responsible for dead arm disease on grapes in the Manutuke Valley, Gisborne, and at Henderson and Te Kauwhata in the Auckland Province. Berry-Smith (1962) recorded it on the varieties `Albany Beauty', `Black Hamburg', and `Palomino': He recommended using sprays with P.M.C. for its control. It is responsible for considerable damage to vines.

Type: Caulicolous Fungi; Caulicolous Fungi; Description: Conidiomata stromatic, pycnidial to acervular, scattered to gregarious, occasionally confluent, partly erumpent, roughly circular to oval, black, 0.2–0.4 mm in diameter, opening by an irregular split; on cankers on stems and branches. Conidia fusiform, straight, 5-septate, 21–30 × 8–10 μm, smooth, apical and basal cells hyaline to subhyaline, intermediate cells brown to dark brown; apical cell with a single, tubular, short (0.5–1.5 μm) appendage; basal cell appendage when present single, centric, 1 m long.

Distribution: Auckland, Bay of Plenty, Taranaki, Taupo, Rangitikei, Wanganui, Wellington, Gisborne, Wairarapa, Nelson, Buller, Westland, Marlborough, North Canterbury, Mid Canterbury, South Canterbury, Dunedin, Southland.; 1st Record: Birch (1933: as Coryneum cardinale).

Notes: Swart (1973) considered that differences in the characteristics of conidial appendages used to distinguish S. cardinale (appendages <2 μm long or absent) from S. unicorne (appendages up to 10 μm long) represented extreme variations of a single species. This view is not generally accepted. See also NOTE under Seiridium unicorne (p. 135).

Significance: One of the fungi causing cypress canker. Cypress canker is common throughout New Zealand (van der Werff 1988, Hood et al. 2001). The fungi cause cankering on branches and stems, resulting in crown dieback which leads to malformation, reduced wood quality and, occasionally stem breakage. Some mortality has been recorded, particularly in young stands (Hood et al. 2001). No economic evaluation of the losses is available. Conidia are dispersed by water splash. New cankers are initiated if conidia land on wounds or cracks in otherwise healthy tissue. Pruning increased spread of the disease (Self & Chou 1994, Hood et al. 2001). Van der Werff (1988) reported that incidence of cypress canker in Cupressus macrocarpa decreased as tree age increased and increased with a rise in average mean temperature. No correlation with rainfall was found. Hood et al. (2001) observed a gradual increase in severity of the disease from south to north of the country. A farm forester of much experience with cypresses has noted that C. macrocarpa seems to be much healthier on southern slopes and sheltered sites, indicating that site temperature and exposure are important factors influencing disease severity. He also noted that the disease also seemed to be worse on the windward site of a shelterbelt (D.Hocking, pers. comm.). There is considerable difference in susceptibility between the host species (Gilmour 1966a; Hood et al. (2001): highly susceptible—Chamaecyparis lawsoniana, Cupressus macrocarpa; susceptible—×Cupressocyparis leylandii, Cupressus lusitanica; resistant —Cryptomeria japonica, Cupressus arizonica, C. torulosa, Thuja plicata. Records of Seiridium spp. in the Forest Health database maintained by New Zealand Forest Research Institute show that Seiridium unicorne is more common (77%) than S. cardinale (23%). An exception occurs in the Canterbury region (North, Mid and South Canterbury), where records of S. cardinale were as frequent as those of S. unicorne. Most records of S. unicorne are from C. macrocarpa, C. lawsoniana, and ×Cupressocyparis leylandii. Nearly all records of S. cardinale came from C. macrocarpa. Only S. unicorne was recorded on C. lusitanica. Chemical control of cypress canker is not considered to be necessary. Resistance to this disease is one of the criteria used in the selection of superior individuals of C. macrocarpa for tree improvement field trials (Gea & Low 1997).; Host(s): Chamaecyparis lawsoniana, ×Cupressocyparis leylandii, Cupressus arizonica, C. macrocarpa, C. sempervirens, Thuja plicata.