HOSTS AND HOST-FUNGUS RELATIONSHIPS
Daldinia species are probably
exclusively angiosperm associates. In the recent compendium on fungi on plants and plant
products in the US, Daldinia
concentrica is listed on 21 dicot host genera and D. vernicosa
(Schwein.) Ces. & De Not.-considered a synonym of D.
fissa C. G. Lloyd herein-is reported on 17 dicot host genera (Farr et
al., 1989). A report of D.
concentrica on bamboo represents an erroneous identification (see elsewhere
herein). Host records for D. concentrica and taxa likely
to be confused with it, such as D.
petriniae Y.-M. Ju, J. D. Rogers, & San Martín in Europe, show
great similarity to those from the US (Cannon et al., 1985; Petrini and Müller, 1986;
Saccardo, 1897). Several species are known only from monocots. These include D.
bambusicola Y.-M. Ju, J. D. Rogers, & San Martín, D.
graminis Dargan & Thind, and D.
sacchari Dargan & Thind.
There seems to be at least some host specificity among those Daldinia species occurring on woody dicots. Daldinia concentrica occurs very commonly on Fraxinus in Great Britain (Cannon et al., 1985) and is frequently encountered on Betula species in the beech-birch-maple forests of northern US and Canada (personal observation, JDR). Whalley and Watling (1980) reported D. vernicosa as highly specific for burnt Ulex wood in Great Britain. That fungus is considered to be D. caldariorum Henn. herein, but it seems possible that it is a distinct taxon based upon its great host specificity (Whalley and Watling, 1980).
Daldinia concentrica, like most if not all xylariaceous fungi, causes a white rot of host wood, i.e., both cellulose and lignin are degraded (Cartwright and Findlay, 1950; Rogers, 1979). The decay caused by xylariaceous fungi is very similar to those caused by white-rotting basidiomycetes (Sutherland and Crawford, 1981). Merrill et al. (1964) found that sterile wood blocks are decayed more slowly by D. concentrica than by some basidiomycetes, but the appearance is similar. Nilsson and Daniel (1989) reported that D. concentrica caused a weight loss of 62.9% in birch (Betula) wood after 2 months exposure to the fungus. Panisset (1929), in proving D. concentrica to be the cause of "calico wood" in ash (Fraxinus excelsior), has given a good account of the microscopical aspects of decay.
Daldinia species are probably weak facultative parasites that continue to decay the wood following decline and death of their hosts. Hepting (1971), in his monumental review of diseases of forest and shade trees in the United States, makes only one reference to Daldinia-an unidentified species on declining oaks. It thus appears that there is no concern about Daldinia species as damaging pathogens, at least in the US. Boddy et al. (1985) have shown D. concentrica to be a common inhabitant of branches of Fraxinus excelsior in Great Britain. They suggest that it is a primary colonizer, perhaps remaining latent for a period prior to extensive colonization.