Armillaria species on small woody plants, small woody debris, and root fragments in red pine stands

Abstract

The incidence of Armillaria on small woody plants, small woody debris, and root fragments was estimated in red pine (Pinus resinosa Ait.) stands in northeastern Minnesota. Soil core samples 10 cm in diameter, and extending to a depth of either 16 or 25 cm, were collected from 13 stands belonging to three age-classes. Half of the youngest stands had been treated using herbicide. Mycelial fans or rhizomorphs of Armillaria were observed on 13% of the small woody plants and isolated from 8% of them. Including small woody debris and root fragments, 38% of 0–16 cm deep samples had Armillaria. Armillaria was observed on 3% and isolated from 1% of individual substrate units from 0 to 25 cm deep samples. Within a single stand, 0%–67% of the samples and 0%–9% of the individual units had evidence of Armillaria. All but one isolate were Armillaria ostoyae (Romagn.) Herink. Herbicide-treated and untreated red pine stands had similar Armillaria incidence, and there was a trend of incidence inversely related to stand age-class. Large numbers of small woody plants, woody debris, and root fragments were found in red pine stands; varying percentages of these substrates were contributing to the survival of Armillaria and could also be serving as sources of root disease inoculum.

Survival time analysis of Pinus pinaster inoculated with Armillaria ostoyae: genetic variation and relevance of seed and root traits

“…Conversely, secondary roots infected and girdled by A. ostoyae may not offer enough inoculum potential to overcome even weak host response (Robinson and Morrison 2001). Accordingly, fine roots are not as susceptible to Armillaria root disease as woody roots (Baumgartner and Rizzo 2006), and although fine root fragments may serve as sources of inoculum of A. ostoyae (Kromroy et al 2005) their potential to originate infections in coarse roots has not been assessed yet.…”

Secrets of the subterranean pathosystem of Armillaria

“…tree stumps), and that the resulting haploid mycelium persists saprophytically. Evidence in support of this hypothesis has been provided by the recovery of A. novae‐zelandiae from pieces of Pinus radiata wood acting as traps for wind‐dispersed spores (Hood et al ., 2002), and the recovery of A. ostoyae from naturally occurring woody debris in P. resinosa stands (Kromroy et al ., 2005). As roots frequently proliferate into rotted tree stumps, it is possible that the colonization of such substrates by spores provides an opportunity for the infection of living roots.…”

Towards the Biological Control of Devastating Forest Pathogens from the Genus Armillaria

“…As the ITS sequences did not enable an exact, species-level identification in the case of many Trichoderma isolates, the species identification was set up based on the sequence of a tef1α gene fragment. The isolates proved to represent 14 Trichoderma species: T. simmonsii (17), T. koningii (11), T. virens (8), T. atroviride (8), T. atrobrunneum (7), T. asperellum (3), T. hamatum (2), T. citrinoviride (2), T. tomentosum (1), T. paratroviride (1), T. crassum (1), T. guizhouense (1), T. paraviridescens (1), and T. longipile (1) ( Table 1). The diversity of Trichoderma species showed a difference between the two forests.…”

“…It is well known that most Armillaria species exhibit specialization towards either coniferous or broadleaf hosts. Although native coniferous forests in the Northern hemisphere are predominantly inhabited by A. ostoyae and A. cepistipes, various oak and other broadleaf species are most exposed to A. mellea, A. gallica, and Desarmillaria tabescens [6][7][8].…”