Japanese Beetle

What is the Japanese Beetle?

The Japanese Beetle (Popillia japonica) is an invasive insect pest that can cause some pretty nasty damage to your favorite ornamental trees and shrubs.  It eats the tender tissues between the veins of the leaves of plants that it attacks and all that's left of the leaves are the brown, skeletal remains. 

 

How did the Japanese Beetle get to the United States?

The Japanese beetle is native to Japan. The insect was first discovered in the United States in 1916 near Riverton, New Jersey in a nursery.  It is thought that beetle larvae got into the United States in a shipment of iris bulbs before inspections of imported goods entering the country began in 1912. 

What kind of plants do they eat?

While they have been found to attack a wider variety of plants, Japanese Beetles are especially attracted to sweet smells and, as such, particularly enjoy rose bushes, linden trees, grape vines, canna, and crape myrtle.

 

How can we control them?

There are many ways to control the Japanese Beetle population around your yard.  These include:

  • Hand pick and dispose of the first beetles you see, usually in late June and July.  These first beetles send out pheromones that attract more beetles to the area.
  • Plant species that are less attractive to the beetles, such as arborvitae, baby’s breath, begonia, bleeding heart, buttercups, columbine, catnip, chives, garlic, tansy, daisies and flowering dogwood.
  • Japanese Beetle traps attract the beetles with flowery scents and pheromones.  Caution: Some studies have shown a trap may actually increase the number of beetles in your area and could possibly increase the damage.
  • There are also insecticides you can purchase at your local garden center to kill the adult beetles.
  • During the early spring and into early June, you can use a product containing a bacterium called Milky Spore (Paenibacillus popilliae) which attacks the Japanese Beetle in its larval stage.  While this is a very good natural control, it can take up to five years to be fully effective. 
  • Spreading the remains of dead beetles in areas you want to protect can help deter them, also. 


Will my trees and plants survive being eaten by the Japanese Beetles?

Japanese Beetles can cause significant stress to trees and plants.  Repeated infestations year after year can worsen this stress.  Depending upon many other factors, the trees and plants may begin a slow process of decline.