The emerald ash borer (Agrilus planipennis) is an invasive insect pest in North America and is just one example of an invasive species that threatens plants outside its native range. To better enable prevention of and response to such invasive pests, entomologists and plant-protection experts around the world share knowledge through a variety of online early warning systems, a variety of which are profiled in a new guide in the open-access Journal of Integrated Pest Management. (Photo by Sandrine Corriveau, via iNaturalist, CC BY-NC 4.0)