Farmer beetle finds suitable host trees by tracing scent of its fungus crop

The alnus ambrosia beetle Xylosandrus germanus, also known as the black stem borer, was accidentally introduced by humans from its native east Asia to North America and Europe around the beginning of the 20th century. X. germanus is a so-called ambrosia beetle, which means that it farms its own food, a specialized fungal symbiont that it "sows" and tends inside the galleries that it digs inside wood. The ambrosia beetle is a destructive invasive pest, known to attack more than 200 species from 51 families of broadleaf and conifer trees. While it prefers to colonize dead wood, it can also infest and ultimately kill weakened or stressed trees.