Japanese Beetles

Jul 03, 2020

Japanese Beetles, the nuisance in everyone’s gardens and flower beds! If these little pest have invaded your backyard, you’re not alone and we, at Colonial Gardens, have a solution.

A Little History

Japanese beetles (Popillia japanicus) first appeared in the United States in 1916 in a New Jersey nursery. Supposedly, the beetles’ larvae came into the US from a shipment of Japanese iris bulbs that the nursery was selling. Even though the US started inspecting overseas shipments in 1912, the beetles’ larvae were not detected until they started multiplying at an incredible rate. While it appears that the insect is now an established part of our garden culture, there are many ways to treat them.

What to Look For

Japanese beetle larvae are a grub that is white and about an inch long, that lie in a curled position underground. They are responsible for damage to turf, home lawns, park green spaces, golf courses, and so on. Look for brown, dead patches of your lawn, that will lift up easily. Using grub control in late-May and early-June is a great way of controlling them in your own yard before they hatch into the adult stage. In the adult form, they can wreak havoc on plants very quickly! Some of their favorite plants include:

  • Roses
  • Crape
  • Myrtle
  • Cannas
  • Linden
  • Malus (apple)
  • Prunus (cherry, plum, peach)

Look for the typically easy to spot greenish-red, metallic sheen of the adults, usually spotted in clusters on the plant. Look also for the leaves on afflicted plants being skeletonized, think of Swiss cheese.


Many products that we carry at Colonial Gardens will treat this voracious beetle! Alternative to sprays are traps if used properly or planting resistant plants.


Bonides Eight Garden and Home spray have been found to be effective at treating them and comes in a ready-to-use hose-end and concentrate form. This will also treat other insects in the garden like ants, aphids, bagworms, and many more! Bug Blaster 2 is another good treatment option, as well as Malathion, and Sevin. Another less toxic way to treat them is to fill a pail or bucket halfway with soapy water, walk around the afflicted plant and tap the bugs into the bucket where they drown! The predators that eat the grubs and adult form of the beetles include spiders, other predator bugs, and many types of birds like robins, crows, sparrows, cardinals, and blue jays.

If left untreated the insects will quickly strip a favorite tree or shrub of its foliage in as little as 5-7 days! While this often doesn’t kill the plant, the lack of foliage for photosynthesis can weaken the plant, making it more susceptible to further attacks from insects or pathogens. Always spray your plants before 7am or after 7pm to limit the exposure of insecticides to beneficial insects and pollinators.


Over the last few years, the use of Japanese Beetle Traps have been sold in droves as a way to eliminate the insect from our yards and gardens. They were developed to track and capture the beetle as an early detection method many years ago. The traps use a very potent pheromone to attract the insects to the traps and can attract them for over a half-mile away! We suggest only using traps if you have a large property and placing your trap the furthest away from the trap. If your only alternative is to use a trap, place the trap away from your plants and garden.

Resistant Plants

Woody Resistant Plants

  • Red Maple
  • Boxwood
  • Hickory
  • Redbud
  • Sweetgum
  • Dogwood
  • Lilac
  • Magnolia
  • Spruce
  • Juniper

Herbaceous Resistant Plants

  • Hosta
  • Coral Bells
  • Poppy
  • Columbine
  • Begonia
  • Lily of the Valley
  • Coreopsis
  • Impatiens
  • Lantana
  • Moss Rose

Know that you’re not alone in the fight against Japanese Beetles. The experts at Colonial Gardens are here to answer your questions and help find a solution to keep your plants healthy throughout the season.