Changes occurring in the macromolecular traits of wood cell wall components of elm (Ulmus species) following an attack by Ophiostoma novo-ulmi (Dutch elm disease) are poorly understood. Ďurkovič et al. examine two elm hybrids with contrasting survival strategies upon infection with the current prevalent strain of the disease (ssp. americana × novo-ulmi) and find that the syringyl-to-guaiacyl ratio in lignin affects the degradability of cellulose by cellulolytic enzymes. When infected, the hybrids respond to medium-molecular weight cellulose degradation with the biosynthesis of high-molecular weight macromolecules of cellulose, resulting in an increase in values for the degree of polymerization and polydispersity. However, only guaiacyl-rich lignin in the tolerant hybrid is involved in a successful defence against the fungus.