Visible versus actual incidence of Armillaria root disease in juvenile coniferous stands in the southern interior of British Columbia

Abstract

The relationship between aboveground symptoms and belowground incidence of Armillaria ostoyae (Romagn.) Herink on conifers in 13-to 24-year-old stands was investigated at five sites in each of the dry, moist, and wet climatic regions in the Nelson forest region, British Columbia. All trees >1.3 m in height in 0.01-ha circular plots centred on a tree killed fewer than two or more than five years previously or located where there were no symptomatic trees were removed from the soil by an excavator. The location and host response at each A. ostoyae lesion on root systems were recorded. Significant differences in belowground incidence were seen among climatic regions and plot types, with distance from the centre of plots, and between planted and naturally regenerated trees. Belowground incidence was related to the percentage of putatively colonized stumps within and adjacent to plots. There were significant differences among climatic regions in the intensity of infection, host reaction to infection, and percentage of diseased trees showing aboveground symptoms. These results have implications for interpreting results of surveys for Armillaria root disease in juvenile stands and for tending of such stands.Résumé : Cette étude porte sur la relation entre les symptômes présents sur les parties aériennes et l'incidence d'Armillaria ostoyae (Romagn.) Herink sur les racines de conifères dans des peuplements âgés de 13 à 24 ans. L'étude a été réalisée dans cinq sites dans chacune des zones climatiques sèche, semi-humide et humide, de la région forestière de Nelson, en Colombie-Britannique. Tous les arbres plus hauts que 1,3 m dans des parcelles circulaires de 0,01 ha ayant comme centre un arbre mort il y a moins de deux ans ou plus de cinq ans, ou se trouvant dans un lieu exempt d'arbres portant des symptômes, ont été extraits du sol avec une excavatrice. La position des lésions dues à l'A. ostoyae sur le système racinaire et la réaction de l'hôte ont été notées. L'incidence du champignon sur les racines différait significativement selon la zone climatique, le type de parcelles, la distance à partir du centre de la parcelle et selon que les arbres avaient été plantés ou provenaient de la régénération naturelle. L'incidence du champignon sur les racines était reliée au pourcentage de souches apparemment colonisées à l'intérieur ou à proximité des parcelles. La sévérité de l'infection, la réaction de l'hôte et le pourcentage d'arbres malades montrant des symptômes sur les parties aériennes étaient significativement différents selon la zone climatique. Ces résultats peuvent avoir un impact sur l'interprétation des résultats des relevés du pourridié-agaric dans les jeunes peuplements et sur la façon de traiter de tels peuplements. Morrison et al. 414

Resistance and tolerance in juvenile interior Douglas‐fir trees Pseudotsuga menziesii var. glauca artificially inoculated with Armillaria ostoyae

“…This results in long-term, persistent and sustained disease in host plants. As most interior Douglas-fir trees eventually exist in a diseased state (Morrison et al 2000, disease tolerance would be attractive from several practical standpoints. Lack of timber product uniformity is one of the greatest problems faced by wood-use industries (Bowyer et al 2007), and wood quality, product recovery and piece size, all related to growth, are important determinants of Douglas-fir product value.…”

“…Mortality usually takes place after multiple attacks that eventually reach and girdle the root collar; hence, trees remain alive for some time. The disease epidemiology causes many more infected trees to remain alive but infected below ground than are dead (Morrison et al 2000. Therefore, the costs of defence reactions against this fungus are of importance.…”

Yield reduction in spruce infected with Armillaria solidipes in the southern interior of British Columbia

“…in spruce forests of Canada: 41% of spruce trees had infected roots, a relationship that increased with tree age (Whitney 1995). Similar disease incidence occurs in British Columbia (BC) for conifers infected with A. solidipes including spruce (Morrison et al 2000(Morrison et al , 2001. Management practices that regularly create stumps exacerbate the problem by increasing the quality and quantity of fungal inoculum on sites.…”

“…Tree volume at age 10 was used as a measure of healthy growth for all trees before disease. Size is important because growth becomes increasingly confounded with disease over time (Bloomberg and Morrison 1989), and disease is more common on larger trees (Bloomberg and Morrison 1989;Morrison et al 2000). The model used to determine volume yield reduction took the form of:…”

Re‐evaluation of Armillaria and Desarmillaria in South Korea based on ITS/tef1 sequences and morphological characteristics

“…Root diseases caused by A. mellea, A. ostoyae and D. tabescens cause significant damage to woody plants globally (Baumgartner et al, 2011;Hood, Redfern, & Kile, 1991;Williams-Woodward, 2013 Korean forests might be due to the presence of fewer susceptible tree species in these locations (e.g., Hood et al, 1991;Morrison & Mallett, 1996), a high ratio of adapted, mixed forests in South Korea or lack of close inspection; however, Armillaria root disease can also cause reduced forest growth in the absence of readily observable symptoms (Cruickshank et al, 2011;Morrison, Pellow, Norris, & Nemec, 2000). Both A. ostoyae and D. tabescens represent potential threats to South Korean forests, and these threats could be exacerbated by climate change (Klopfenstein, Kim, Hanna, Richardson, & Lundquist, 2009;Sturrock et al, 2011).…”