The emerald ash borer is a green beetle native to eastern Russia, northern China, Japan, Taiwan, and the Koreas. In 2002, they were first discovered in North America and have since become an invasive species. They are estimated to have killed about 100 million ash trees in eastern Canada and much of the eastern part of the United States.
These scented purple traps are used to detect the presence of the beetles. The beetles are attracted to the purple color and the scent. The inside of the trap is covered in a sticky glue.