Armillaria fungi are among the most devastating fungal pathogens, causing root rot disease in more than 500 plant species found in forests, parks and vineyards. As white rot fungi, they are capable of breaking down all components of plant cell walls, a capability that interests bioenergy researchers. Biologists have now analyzed and compared four Armillaria fungal genomes with those of related fungi to better understand the evolution of Armillaria’s abilities.