Beetle 101

Each year WSDA deploys over 1,500 traps to monitor for Japanese beetle. The program traps around nurseries and farms throughout the state. However, most traps are placed at potential pathways, like airports, railways, or transfer stations. Each year a trap or two may catch one beetle. The beetle is then removed and unable to reproduce.  

If any trap were to detect multiple beetles, the response becomes serious, and the potential for Japanese beetle to establish becomes a present concern. Oregon Department of Agriculture estimated that if Japanese Beetle were to establish, the economic impact to their crops, commodities, and other related businesses could be approximately $45.5 million.

Japanese beetles create large-scale destruction to garden plants and agricultural crops. The beetle is a serious threat to many of Washington's thriving industries, including nurseries, turf grass, and specialty crops. WSDA is working hard to eradicate the infestation through trapping, treatment and quarantine. This multi-year effort is to protect Washington's agricultural and recreational livelihood.

An eradication is a project that may follow the detection of a new invasive species. The goal would be to remove all life stages from the area and stop the pest from becoming established.

It will take multiple years. Other western states that have performed eradications over multiple years. Treatment areas may shift from time to time assuming that beetles will disappear from places where treatment has been successful. They may also move to infest untreated areas, since they are capable of flight. They can also be transported to new area as “hitchhikers” on transport vehicles or through the movement of yard waste.

Japanese beetle is a scarab beetle native to Japan. It was first found in New Jersey in 1916. Since that time it has slowly spread and become established in about half of the country, primarily in the Eastern U.S. Both Washington and Oregon are currently attempting to eradicate Japanese beetle introductions. Idaho recently successfully eradicated an introduction. 

Invasive species have pathways, which are the means and routes by which invasive species are introduced into new environments. As an adult Japanese beetle can move many miles by hitchhiking on airplanes, trucks, and trains. Their larvae hide under the soil and be spread by moving potted plants, compost, grass clippings, or fill.

You can protect their gardens by placing a trap near the garden to capture any beetles that may emerge. The beetles will eat on their way to the traps, and around the traps so don't place a trap directly next to your favorite plant.

Adult beetles are also safe to touch as they do not sting or bite. You can pick adult beetles off vegetation and drop them in a bowl of soapy water. It is best to do this in the morning or evenings when beetles are less active. 

If you detect beetles and would like to treat your garden, Washington State University Extension produced homeowner control options. The type of treatment depends on the time of year due to the pest’s life cycle. Do not treat for beetles if you have not detected beetles.

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The beetles have one generation per year. Eggs are laid in the soil during the summer. Grubs will hatch from the eggs and feed through the fall and then hibernate until spring. When weather warms enough the grubs become pupae. Soon the adults emerge around June and begin the cycle again. Adults live about a month.