How to treat Japanese Beetles

How to treat Japanese Beetles

June 28, 2018

How to treat Japanese Beetles

It’s a beautiful mid 80’s day in the Midwest, the sun is shining, birds are chirping, and your neighbor finally decided to trim their overgrown tree that was draping into your yard!  You walk outside to check on your picture-perfect garden, only to find it’s infested with BEETLES!!!!

Japanese Beetles first appeared in the United States in 1916 and are believed to have hitchhiked to the United States in a shipment of iris bulbs.  Unfortunately, their natural predators in Japan did not come with them which means they have freely multiplied and spread.

Japanese Beetles start off as larvae and molt into adults. They typically come out of the ground in spring and into early summer to chew on your plants. They tend to cause damage to your plant’s foliage…leaving you sad, lacy-looking leaves


When it comes to Japanese Beetles, understanding their life cycle is critical to knowing when to apply the right product.  Adult females lay eggs in the ground from late June to early August; she can lay up to 8-10 eggs every night during her life!   The eggs hatch into larvae that eat your grass roots in late summer into fall (you might start seeing large brown spots on your lawn).  They go dormant in winter and then rise to the soil surface in late spring through early summer and emerge as adults to chew your plants, trees and flowers.

Selecting the right product for your situation is important.  Did you know that sometimes organic insecticides can be more harmful than synthetic?  Even though the bottle says it’s “organic” that doesn’t necessarily mean it cannot harm beneficial bugs, pets or humans. While some synthetics are copied from natural compounds found in nature.  You should always know exactly what you’re spraying on your plants depending on if they are edibles, flowers, trees or shrubs. The experts at Colonial Gardens have suggested a few of their favorites:


Japanese Beetles-Larvae





Apply these products in June.  Use grub control, granular lawn treatment for the larvae stage of the Japanese Beetle. A few suggestions include:

Pro Mate Lawn Food with Grub Control

High Yield Grub Free Zone 2







Apply these products mid-June through early August.  There are a variety of ways to treat adult Japanese Beetles. A few suggestions include:


Captain Jack’s

Broad Spectrum

Japanese Beetle Traps

Japanese Beetle Traps – These traps are most effective when used by an entire neighborhood or community as they use pheromones that attract large numbers of beetles.  Be sure to place these AWAY from any trees or plants.


To be aggressive and prevent issues to your perennials, trees or shrubs, apply a systemic product in the early spring.

-Imidicloprid (there are a variety of products on the market with this active ingredient)


Japanese Beetles are more of a pest to your plants, than just a bug. Since Japanese Beetles are mobile and travel to many plants a day. They can bring with them diseases and viruses from infected plants that they’ve landed on.

If you are wanting nothing but happy, healthy plants in your garden then it’s important to keep an eye on them. Watch your plants closely each time you water or fertilize them. This can be the difference between happy plants and a pest infestation.

Colonial Gardens carries all these products and our experts will be happy to find the right solution for you!

Article written by

Kevin Keilig,
Director of Greenhouse Operations

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