Metagenomics has illuminated our understanding of how microbial communities influence health and disease. Researchers are beginning to characterize what constitutes healthy microbiota in terms of structure, function, and diversity in a variety of environments. Although investigation lags behind the more well-studied human microbiome, a growing body of research is using next-generation sequencing tools and advances in bioinformatics to explore how microbiota and constitutive microbiomes in soils, and plant tissues can affect crop and forest diseases (Damon et al. 2012, Bonito et al. 2014, Penton et al. 2014, Qiu et al. 2014, Stursova et al. 2014). Disease suppression in agricultural systems has been fairly well-studied, with suppression attributed to diverse microbiota that affect pathogen survival, growth, and infection. In these systems, management practices such as no-till and stubble retention, which supply higher levels of available carbon, have been shown to favor diverse microbial communities. Our understanding of disease suppression in forest soils is minimal, even though these ecosystems are home to some of the most complex microbial communities (Fierer et al. 2012) that play essential roles in biogeochemical cycles (Van Der Heijden et al. 2008) and account for considerable terrestrial biomass (Nielsen et al. 2011). Armillaria Root Disease is one of the most important diseases of trees in temperate regions, yet it remains difficult to manage. Results of biological control research suggest that components of the forest soil microbiota may affect ArmiUaria Root Disease (e.g., Reaves et al. 1990, Reaves and Crawford 1994, Filip and Yang-Erve 1997, Becker et al. 1999, Chapman et al. 2004, Shapiro-llan et al. 2014).