Michigan is the fourth-largest hop producing state in the US. The hops grown here help support a dynamic craft-brewing industry. With support of Project GREEEN, we are working to improve methods of detecting and diagnosing viruses and viroids that can infect hop plants. Apple mosaic virus (ApMV) is one concern. This Ilarvirus in the Bromoviridae family can cause significant yield loss. Sometimes the infection causes characteristic symptoms, such as white rings on hop leaves as shown below, but other times signs of infection remain hidden.