Climate, radial growth, and mortality associated with conifer regeneration infected by root disease (Armillaria ostoyae)

Abstract

Tree root disease caused by the pathogen Armillaria ostoyae (Romagn.) Herink has notable influence on bio-economic systems of southern British Columbia (BC) and the northwestern United States. Annual radial growth and mortality trends of regeneration associated with A. ostoyae during the first 21 years of a plantation were investigated. Our dendrochronological approach focused on a plantation established in 1991 with Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), western larch (Larix occidentalis Nutt.), and lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm. ex S. Wats.). We examined tree rings for reduced growth onset (RGO) to estimate infection periods. Among trees studied, we found that the number of RGO events peaked in 2006 followed by a steady decline in frequency. A similar trend was seen in annual mortality rates which reached maximum values in 2007 followed by an uninterrupted decrease. The average number of years from RGO to death based on host species ranged from 2.3 to 3.6 years. According to on logistic regression modeling, values associated with drought codes and duff moisture codes were significant in determining the year of death for infected trees. The predicted increase in frequency of summer droughts may lead to elevated mortality associated with A. ostoyae in young plantations.

Predicting Present and Future Suitable Climate Spaces (Potential Distributions) for an Armillaria Root Disease Pathogen (Armillaria solidipes) and Its Host, Douglas-fir (Pseudotsuga menziesii), Under Changing Climates

“…Of special note, P. menziesii with higher levels of drought tolerance were also associated with higher levels of resistance to Armillaria root disease, caused by A. solidipes (Cruickshank and Filipescu, 2017). Furthermore, summer droughts were associated with increased A. solidipes-caused mortality of P. menziesii in southern BC, Canada (Murray and Leslie, 2021). These findings further support that climatic maladaptation of P. menziesii will lead to increased infection by A. solidipes.…”

“…Changing climate, extreme weather events (e.g., drought, high temperatures), and/or other disturbances (e.g., fire, insect attack, and forest management activities) are causing increased disease severity by A. solidipes on stressed P. menziesii (Morrison, 2011;Murray and Leslie, 2021). Armillaria root disease, in conjunction with the adverse impacts from climate and extreme weather events, can predispose trees to attack by other biotic agents including bark beetles (e.g., Hertert et al, 1975;Kulhavy et al, 1984;Tkacz and Schmitz, 1986), which can result in tree mortality and increased availability of nutritional substrates for inoculum of Armillaria species that can, in turn, contribute to future disease on the site.…”

“…In western North America, Armillaria root disease caused by A. solidipes is common on trees that are ecophysiologically maladapted (stressed by environmental factors), which can be attributed to climatic maladaptation and/or other disturbances (McDonald et al, 1987a;McDonald, 1990;Murray and Leslie, 2021). Projections of climate change in the northwestern United States predict an increase in the frequency and intensity of drought and higher temperatures that will result in more stressful environmental conditions for forest trees (Chmura et al, 2011).…”

Applications of a conceptual framework to assess climate controls of forest tree diseases

“…These factors contribute to inoculum quantity and quality, which needs to be assessed to account for changes in disease behavior. However, Murray and Leslie (2021) showed that levels of Armillaria root disease intensity are associated with drought events where the disease is present in a plantation in southern British Columbia (i.e., Type 2 climate–disease). Some root diseases such as laminated root rot caused by Coniferiporia weirii (formerly Phellinus weirii ) are not associated with host stress and any climate effects on disease behavior may be related to vegetative growth and sporulation similar to stem decay fungi (i.e., Type 1 climate–disease).…”

Genomic innovation and horizontal gene transfer shaped plant colonization and biomass degradation strategies of a globally prevalent fungal pathogen

“…Known at the genus-level as Armillaria root-rot disease [3][4][5] , the most common pathogenic species is A. mellea sensu lato, which has been reported to infect >500 plant species 1,6,7 and is solely responsible for up to 40% annual loss of vinegrape in California 8 . A. ostoyae is responsible for significant losses in conifer forests 9,10 .…”