Infection of Picea sitchensis and Pinus contorta stumps by basidiospores of Heterobasidion annosum

Abstract

Infection of Pinus contorta and Picea sitcbensis stumps by basidiospores of Heterobasidion annosum is extremely variable, both within and between sites, but in general P. sitchensis stumps are less susceptible than those of P. contorta. Measurement of the cross-sectional area occupied by H. annosum on each stump provides a more sensitive test of species susceptibility than assessment of the proportion of stumps infected. P. sitchensis stumps become infected on a variety of soils but there is evidence to suggest that infection may be reduced by high rainfall.In some infected stumps, H. annosum is confined to the lower stump tissues. Its absence from the upper portion of the stump may be due to replacement by other micro-organisms or, alternatively, physical conditions in the upper stump tissues may prevent its continued survival after infection has taken place. In both species, but more commonly in P. sitchensis, some stumps remain alive for at least two years after felling, particularly on peat soils, due to the presence of root grafts with neighbouring trees. Results for P. sitcbensis suggest that infection occurs more readily in living stumps than in those which die rapidly after felling.The viability of H . annosum basidiospore suspensions can be determined more accurately and more rapidly on a selective agar medium than on conifer stem sections.

Incidence of Heterobasidion annosum in precommercial thinning stumps in coastal British Columbia

“…In common with similar studies of stump colonization (REDFERN 1982(REDFERN , 1993REDFERN et al 1997), this study recorded large within factor variation for both incidence and area colonized. This variation may have obscured differences within factors such as season and biogeoclimatic subzone.…”

“…Precipitation as rainfall could affect spore infection of stumps by washing spores from the air (REYNOLDS and WALLIS 1966) and by washing spores from the stump surface before infection can occur (REDFERN 1982). However, availability of spores appears not to have a major effect on incidence of H. annosum because stumps became infected in the wettest seasons and subzones in this study, and REDFERN (1993) found that covering stumps for 24 h after inoculation did not result in a high incidence of infection in a high rainfall area.…”

Infection of pre-commercially cut stumps of <i>Picea abies</i> and <i>Pinus sylvestris</i> by <i>Heterobasidion</i> spp. – a comparative study

“…High variability in area of colonized stump wood has been noted even in artificially basidiospore-inoculated stumps, as e.g. of Sitka spruce (0.02-56.6%) (Morrison and Redfern 1994) and lodgepole pine (3-96%) (Redfern 1982).…”

Inoculum concentration and the colonization of picea sitchensis stumps by basidiospores of heterobasidion annosum

“…Meredith (1959) used the same concentration, and Kuhlman & Hendrix (1964) used 1.4 x 1.0 3 viable spores ml" 1 . Redfern (1982Redfern ( , 1993 used suspensions containing up to 160 x 10 4 viable spores ml" 1 , equivalent to 1090 x 10 4 spores dm" 2 of stump surface. Direct comparison of these figures with the effective inoculum dose from natural sources is not feasible because this depends on the period during which stump surfaces remain receptive to spores.…”