The study of plant microbe interactions has revealed a great deal to us about the mechanisms of plant diseases and allowed us to develop new tools and strategies that will be critical in ensuring crop health and food security in the face of changing environment and land use. In this talk I’ll cover a wide range of biological systems in which we’ve used mathematical approaches to begin to tackle (but by no means yet solve) some interesting problems. In particular I’ll describe the evidence we have for a large scale small RNA network in Arabidopsis, a Facebook game that revealed how we might better approach crowdsourcing and citizen science, a kinetic model for genome expansion in pathogen host jumps and a method for detecting genetic variation based on searches of coloured de Bruijn graphs.