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Nectria Canker

Nectria cinnabarina (Tode ex Fr.) Fr.
(anamorph = Tubercularia vulgaris Tode ex Fr.)

Ascomycotina, Hypocreales, Hypocreaceae

Distribution: Nectria cinnabarina is widely distributed throughout the range of its hosts in B.C.

Hosts: Species of Nectria that cause cankers and dieback are common on a wide range of hosts, mostly hardwoods. In B.C., N. cinnabarina has been found on vine and bigleaf maple, horse chestnut, mimosa, red alder, saskatoon, quince, Choisya, Pacific dogwood, hazelnut, Cotoneaster, fig, honey locust, apple, plum, cherry, pear, buckthorn, blackberry, willow, mountain ash, Spiraea, western hemlock, and elm. The reader is referred to Farr et al. (1989) for the extensive listing of N. cinnabarina hosts elsewhere in North America.

Identification: The initial symptoms of infection generally appear in the spring with sudden wilting of leaves or the failure of leaves to appear. Sunken cankers are generally associated with wounds or at the bases of dying branches, and may girdle branches or small stems. Bark within cankers dies and appears dry and cracked.

The most prominent sign of infection is the presence of masses of orange-pink coloured "coral-spots" for which the disease is named (Fig. 45a). These are conidia-producing fruiting structures, called sporodochia, which develop through cracks or natural openings in the cankered bark in the spring and early summer. They range in size from 0.5-1.5 mm in diameter and height. Young sporodochia are pink-orange to purplish-red when young, and become tan-to-brown or black as they mature. Later in the summer, orange-red coloured sexual fruiting structures, perithecia, form in groups around sporodochia. Perithecia are globose, approximately 0.4 mm in diameter, with a rough outer wall (Fig. 45b).

Microscopic Characteristics: Perithecia red, clustered on the top edge of an erumpent conidial stroma, globose, slightly collapsed at the ostiole, rough outer wall, 400 m in diameter. Asci cylindric clavate, 8-spored, 60-90 x 9-14 m. Ascospores elliptic-cylindric, hyaline, slightly constricted at the single, central septum, 12-20 x 4-9 m. Sporodochia pink to light red, erumpent through the bark, cushion-shaped, up to 3 mm in diameter. Phialides subulate, 20-30 x 2-4 m, arising from the pseudoparenchymatic stroma, densely packed. Conidia oval to cylindric, 5-7 x 2-3 m, produced in large masses and supported in a mucous matrix.

Damage: Nectria cinnabarina acts mostly as a saprophyte, living on dead plant tissue, and as such is not generally considered a serious forest disease organism. However, it is also weakly pathogenic, colonizing stems and branches weakened by mechanical injury, physiological stress, or other disease. Damage by this fungus is often observed on recently transplanted ornamental shrubs and trees.

Remarks: Two other related Nectria species cause notable cankers on hardwoods, but occur much less frequently in B.C.: N. galligena Bres. in Strauss causes perennial "target" cankers on many hardwoods and fruit trees (European canker) (Fig. 45c), and N. ditissima Tul. causes large perennial stem cankers on red alder (Fig. 45d). Isolates of N. ditissima are being considered as biological control agents for red alder.

References:

Funk, A. 1981. Parasitic microfungi of western trees. Can. For. Serv., Inf. Rep. BC-X-222.


Figures

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Sporodochia of N. cinnabarina - Click to see a larger version of this image

Figure 45a: Sporodochia of N. cinnabarina.

 

 

 

Perithecia of N. cinnabarina - Click to see a larger version of this imageFigure 45b: Perithecia of N. cinnabarina.

 

 

 

 

"Target" canker caused by N. galligena - Click to see a larger version of this imageFigure 45c: "Target" canker caused by N. galligena.

 

 

 

 

A perennial canker on red alder - Click to see a larger version of this imageFigure 45d: A perennial canker on red alder caused by N. ditissima.