Japanese beetles were accidentally introduced in the United States in 1916, they were discovered in a nursery in Riverton, New Jersey at that time. All eradication programs halted in 1920 after they had spread too far to stop them safely. Japanese Beetles have now spread as far west as the Mississippi River and because of the ideal soil and heat conditions in all these areas these pests will be haunting crops for years to come.
In the early part of summer, you will see lots of these metallic green colored beetles just pop up taking over fields, lawns, and trees.
So what do Japanese Beetles Eat? Japanese beetles will eat more than 300 types of plants, including tree leaves, ripened fruit-bearing plants (gardens or crops), blossoms, and vines. In their larval stage, they feed on roots and many types of grass. Optimal weather for activity and feeding is in the hot summer heat, and they usually eat in large groups ranging from a few hundred to thousands when they do.
As japanese beetles will skeletonize a myriad of leaves on hundreds of species of plants and with no known predators to boot these pests will take down a crop, field, tree, or turf in a short couple months of eating. The term strength in numbers comes to mind when thinking of these beautiful looking horrible creatures.
What Is The Life Cycle Of A Japanese Beetle?
There are only 4 stages in the life cycle of a Japanese Beetle which is Egg, Larva/Grub, Pupa, and Adult. So I charted up the stages within these stages to give you a perfect account of timing, behavior, and treatment within those times. I went into further detail below the chart to explain treatment more.
*Note: The Larva/Grub stage can be subdivided into an extra 3 stages and is the longest stage of a Japanese Beetle life cycle. The Larva once hatched is a Dormant Grub, then becomes a Feeding Grub!
| Life Cycle | Behavior | Time | Treatment Options |
| Egg | Eggs are laid 2-3 inches into the soil by adult female japanese beetles and they stay there until they hatch into larva | July – September | Imidacloprid Granules applyw/ a spreader |
| Larva | Once hatched into larva these will feed in the remaining warm months on the grassroots beneath where they were laid causing damage to the lawn/turf | Late August – October | Bifenthrincan be mixed in a one-gallon spray can and sprayed evenly across the grass or turf. |
| Grub | Dormant Grub- In the cold months will burrow down 12” into the soil to overwinter.Feeding Grub- In spring will continue to feed on tree roots, turf, and grass. | October – April | Milky Spore Lawn Spreader Mix– This mix was created in 2011 and specifically treats the grubs of japanese beetles. This treatment lasts in the soil for 10 years |
| Pupa | Once the feeding grub has the nutrients it needs it starts its metamorphosis from a pupa to an adult this is called pupating. | April – Early June | Imidacloprid Granules apply w/ a spreader |
| Adult | The fully grown adult beetles emerge from the soil start to feed and mate and lay more eggs. | Late June – Early August | Ferti-Lome Tree and Shrub- This is a systemic pesticide that revitalizes tree and shrub growth when applied at the root level of either. |
When the female beetle is laying eggs, she will lay 1-5 eggs at a time somewhere between 2-3 inches into the soil. The female Japanese Beetle will stop eggs laying around the 60 egg range.
Since the female Japanese Beetle only lives 30-45 days she will mate, forage, and lay her 60 eggs all in just over a month.
So the life cycle of the japanese beetle takes a year. Since they are so successful at reproducing they are almost impossible to control without the use of a pesticide.
How Do I Treat For Japanese Beetles?
I have been in the pest industry for several years and have learned what to do and what not to do. So, when it comes to using the correct treatment for Japanese Beetles I feel confident in being able to express share just how you can do this on your own.
So, what can I do to treat for Japanese Beetles? You should start by treating the areas where Japanese beetles are present. Use a Systemic Pesticide with Imidacloprid as the active ingredient. to treat the trees and shrubs by drenching them at the roots.
It would be hard for the normal consumer or homeowner to see most stages of a japanese beetle, in fact, you probably won’t be able to diagnose this issue until it is in full force.
Lawn Granule Treatment
This is why I recommend using a granule that you spread across the lawn, it will stop the new eggs from progressing the following year.
Tree An Shrub Treatment
For the trees and shrubs, you should use Ferti-Lome Tree and Shrub and soak the base of these plants diluting this in buckets of water. This pesticide has imidacloprid and nitrogen in it and helps to kick start the plant back in the right direction and will help it defend itself from disease and bugs.
Fruit and Vegetable Bearing Plants
If you have a crop or garden that you want to protect the best thing to use is Monterey Fruit And Tree Soil Drench this is safe for crops. For grapes, raspberries, flowers, roses, trees, and shrubs. This should be applied once at the beginning of the season to ward of all unwanted pests.
Summary
Japanese Beetles eat over 300 species of plants. They are a very impactful threat to farmers and homeowners with a garden. If left alone the effects will be devastating to your plants.
The life cycle of a japanese beetle takes at least a year they go through their 4 stage process in that time and are very good at surviving during the colder months.
In my professional opinion, if you want to prevent or eradicate japanese beetles, Systemic Pesticides are the very best to use. While these pesticides help reverse disease in plants and turf they also help make the soil a lot healthier for the plants to continue growing. They also protect against a myriad of bugs like mites, aphids, and of course japanese beetles, etc.
You can do DIY Treatment on these bugs now and I hope that you are safe in all your efforts to prevent these mischevious pests.
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