Japanese Beetle, Popillia japonica, has been an invasive species in the US for a century. Japanese beetle was first reported in the US in 1916. We believe that Japanese Beetle entered the US prior to 1912, probably as larvae or pupae in soil associated with nursery plants. In 1912, USDA first started inspecting for invasive species. Prior to that time, the problem was not comprehensively addressed. Japanese Beetle may have entered the US just prior to the start of inspections. Since 1916, the Japanese Beetle has slowly spread from the East Coast of the US to the Mississippi River (see PestTracker Map).
As discussed in a previous post, the Japanese Beetle spends most of its life (late summer through late spring) underground as egg, larvae and pupae. By itself, the beetle spreads a few miles every year. Assisted by man, Japanese beetle can travel thousands of miles in a day as a hitchhiking adult on an airplane or hitchhiking larvae and pupae in soil associated with nursery stock. When Japanese Beetles first came to Indiana, large numbers of beetles emerging from grassy areas next to airport runways led to measures by cargo carriers to prevent beetles from boarding airplanes. Stowaways on nursery stock can be minimized by shipping “bare root” since the beetles are in the soil surrounding the roots.
Recently, the Japanese Beetle has been found in several locations in the Western US. Efforts are underway to eradicate the beetles in some of these areas. This year, Idaho is reporting Japanese Beetles for the first time in Ada and Kootenai counties. Efforts to slow the spread can buy time for Western areas of the US, but the Japanese Beetle will likely establish in these areas eventually. In the meantime, areas that are beetle free are using fewer of the expensive pesticide treatments. Eventually, a more effective means of managing Japanese Beetle may be developed. Fans of roses would appreciate fewer Japanese Beetles.