Plant cells were previously shown to produce an extracellular matrix comprising DNA, protein and polysaccharides that, like animal neutrophil extracellular traps (NETS), captures and kills pathogens. In this study, Park et al. show that a plant pathogen uses extracellular DNases (exDNases) as a defence mechanism against host-secreted extracellular DNA in plant-produced NETs. The authors deleted a candidate secreted DNase-encoding gene in the maize pathogen Cochliobolus heterostrophus and showed that the fungal mutant exhibits reduced virulence on plant leaves and plant roots compared with the wild type. The phenotype was rescued by the addition of exogenous DNase I, and the authors confirmed the DNase activity of the enzyme in fungal culture filtrates, suggesting that the DNase is secreted. Last, secretion and activity of the DNase in the culture medium was induced in the presence of plant tissue. The authors hypothesize that the pathogen deploys the enzyme to degrade plant-secreted DNA.