Japanese Beetle
The Japanese beetle, Popillia japonica Newman, was accidentally introduced to the United States from Asia in the early 1900s. First detected in a New Jersey nursery, it is currently established in 28 states in the United States and has been detected in 13 additional states, 3 Canadian provinces, and at least 3 European nations. Adult beetles feed on over 300 host plant species, including many agricultural commodities such as fruits, field crops, and ornamentals, often causing severe economic damage. We discuss invasion history, ecology, biology, and management options for this invasive pest species in North America.
Figure 1. Life cycle of the Japanese beetle, including (a) eggs, (b) larvae (white grubs), (c) pupa, and (d) adult (credit: DOI:10.1093/jipm/pmz009).
Adult Japanese beetles are around 1 cm long, with a rounded oval shape and a hard shiny green exoskeleton and brown wing covers. The best defining characteristic of this beetle is the six tufts of white hairs running down either sides of the abdomen. Japanese beetle larva rastral setae form a distinct V-shaped pattern, and the anal slit forms a crescent moon, below figure shows its difference with European Chafer, another invasive turf grass invasive soil insect.
Figure 2. Two white grubs. European chafer and Japanese beetle larva (credit: www.mgabc.org)
Potential geographic distributions in Washington State
The Japanese beetle, Popillia japonica, was first detected in southern Washington State in 2020. Widespread trapping efforts ensued, and over 23,000 individuals were collected in both 2021 and 2022 in this region known for specialty crop production. The invasion of Japanese beetle in Washington State is of major concern as it feeds on over 300 plant species and has shown an ability to spread across landscapes. Here we created a habitat suitability model for Japanese beetle in Washington and used dispersal models to forecast invasion scenarios. Our models predict that the area of current establishment occurs in a region with highly suitable habitat. Moreover, vast areas of habitat that are likely highly suitable for Japanese beetle occur in coastal areas of western Washington, with medium to highly suitable habitat in central and eastern Washington. Dispersal models suggested that the beetle could spread throughout Washington within 20 years without management, which justifies quarantine and eradication measures. We believer our timely map-based predictions can be useful tools to guide management of invasive species while also increasing citizen engagement to invaders. We developed this interactive map to facilitate its application, check it out HERE. Our work was heightened in WSU Insider, check this out: Japanese beetles could spread across Washington in 20 years.
Figure 3. Potential distributions of Japanese beetle in Washington State;