This week, Plant Pests and Plant Pathology - we find out what happens when plants get ill, how to understand and prevent the spread of plant disease, and how they can call up an insect army to defend them if they're attacked. We also find out why some horse chestnut trees are going brown before their time, and meet the pesky critter responsible! Plus, a new technique to cleanly edit out and correct errors in the DNA code, how the plague bacterium hasn't changed in 600 years, and why children, but not chimps, choose to work together. Like this podcast? Please help us by supporting the Naked Scientists