Crumenulopsis sororia

C. sororia is an apothecia-forming ascomycete (cup fungus) that causes cankers in the bark and wood of Pinus species in Europe. Its presence in North America is unlikely (Groves, 1969), but it is known to infect native and introduced species of Pinus. Once introduced, its small size, resemblance to related canker-causing species, and spread by airborne spores, would make control difficult.

Groves (1969) considered reports of C. sororia in the USA to be erroneous and a misidentification of Atropellis species. Lack of reports of C. sororia from other countries with temperate climates may be due to the difficulty of distinguishing it from related fungi.

C. sororia has been reported as a pathogen on native and introduced species in various countries (Spaulding, 1961; Manap and Hayes, 1971; Hayes et al., 1981) although incidence and distribution data may not be completely accurate due to confusion with Crumenula pinicola (Hayes and Manap, 1975).

Fructification (production of apothecia on infected parts) results from random outcrossing between strains (Ennos and Swales, 1987). Apothecia appear in the spring and early summer after infection (Hayes, 1980). Pycnidia are also produced in and around the canker (Batko and Pawsey, 1964). In Scotland, ascospores are released in spring to early autumn (May to September) in response to certain weather conditions (Hayes, 1975; 1980). Ascospores can remain airborne, particularly within the tree canopy, until removed by wind or rain (Hayes, 1980).

Morelet et al. (1987) report that leaf scars, particularly on older shoots, are an important infection court on Pinushalepensis. Gremmen (1968) cited bark injuries as points of infection, with frost contributing to their incidence, but it is not clear whether injury is required for infection (Hayes, 1973). Manap and Hayes (1971) list nodes, internodes and branch axils as sites for cankers on Pinus contorta.

Physiology and Phenology

Within the species in a substantial geographic area of Scotland, there is a broad range of sensitivity to inhibitory monoterpenes produced by trees (Ennos and Swales, 1988) and of other fungal characteristics (Ennos and McConnell, 2003), but there is no evidence for adaptation of populations to local conditions (Ennos and Swales, 1991; Ennos and McConnell, 1995).

Environmental Requirements

In Scotland, Hayes (1977) found that incidence of infection on the introduced plantation species, P. contorta, was greatest in climatic zones with less rainfall and longer growing seasons. New cankers were more common on the northern and western sides of stems in those drier and warmer areas, whereas in areas of highest rainfall and shortest growing season, the lowest numbers occurred on the north sides and highest numbers on the western sides. Less infection was observed for southwestern and southeastern aspects. On older trees, conditions needed for infection appeared to be restricted to the lower parts of the stem. Further work on a model (Hayes et al., 1981) confirmed that incidence (% of trees with infection) was related to site elevation, aspect and exposure, but these factors could not explain variation in severity of disease.

Infection of P. contorta was also strongly correlated with the level of soil moisture (Craig and Hayes, 1981). Vuorinen (2000) studied the increase in number of cankers in luxuriant growth of a plantation of Pinus sylvestris in Finland and attributed it to the high humidity in the canopy. According to Morelet et al. (1987), cankers on P. halepensis in France increase in frequency when rainfall is above normal.

Before cankers are large enough to cause shedding of bark, they can be detected by the production of resin that accompanies them, from the first few droplets (Gremmen, 1968) to copious flows (Butin et al., 1995). If mature, the dark-brown to black apothecia in and around the canker must be examined microscopically to differentiate them from those of related species. If the unique spores of the Digitosporium anamorph (Sutton, 1980) can be found in pycnidia in the bark, this will be conclusive. Pycnidia also can be obtained in culture on 2.5% malt agar (Batko and Pawsey, 1964).

Crumenulopsis pinicola differs in having shorter, thick-stalked asci, 65-90(-100) x 10-13(-14) mm, and longer, fusiform ascospores, 18-30 (-35) x 3.0-4.0 mm (Groves, 1969). This saprobic species occurs on dead wood (Gremmen, 1968).

Cenangium ferruginosum is difficult to distinguish from C. sororia until mature apothecia are present (van Vloten and Gremmen, 1953). These lack a stipe and have neither hairs nor scales on the margin. Ascospores are ovate-ellipsoid, hyaline, aseptate, 12-13 x 5-6 mm. In culture, this species produces black “spermagonia” containing hyaline bacilliform spores (van Vloten and Gremmen, 1953). Sinclair and Lyon (2005) describe and illustrate the mature apothecia as yellowish-brown, whereas the early forms are dark.

In the related genus, Cenangium, with species on pine as saprobes or weak parasites, the ascospores are ellipsoid. In Gremmeniella, the ascospores are multi-septate.

Gremmeniella abietina produces falcate multicellular conidia in a mucilaginous matrix from pycnidia on infected pines (Sinclair and Lyon, 2005). The dark-brown apothecia exhibit the differences described for Crumenula abietina (see Taxonomy section). Ascospores are ellipsoid, four-celled, 15.2-16.1 x 3.8-4.7 mm (van Vloten and Gremmen, 1953).

Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.

Cultural Control and Sanitary Measures

More vigorous trees are more resistant (Batko and Pawsey, 1964). Disease occurs more frequently, but not exclusively, in plantations affected by poor soil structure, inadequate drainage, and low fertility, or by damage due to exposure. Such sites should be avoided or conditions ameliorated before and after planting.

Butin et al. (1995) recommends removal of infected trees as a means of control, but the report of an increase of infection after thinning (Vuorinen, 2000) indicates that success is unlikely, at least in plantations.

Host Resistance

Different provenances of Pinus species differ in susceptibility (Hayes, 1977; Stephan and Butin, 1980; Butin et al., 1995). A provenance should be selected for planting that is adapted to the local climate. Gremmen (1968) indicates that bark injury due to frost may increase infection: a provenance adapted to frost would be less susceptible to the fungus.

Whether C. sororia is present in North America is in dispute. No DNA sequences are available in the GenBank database for comparison with those of any specimens. In the case of a new introduction, its likely effect, in competition with other fungi on native species is unknown. The role of the conidial anamorph in the life cycle or epidemiology is unexplored.

10/09/09 Original text by: