If you are looking for a guide to Japanese Beetle, you have landed on the right page.
The Japanese beetle, Popillia japonica was not much of a problem in the United States until about 1919.
This is when this native to Japan began a serious invasion, probably after hitchhiking to North America on imported ornamental plants.
It is important to note that today they tend to be a serious nuisance to gardeners and farmers.
These adult Japanese beetles that eat so many plants are about 3/8 inch long, with a shiny, metallic green body and copper brown wing covers.
However, it is important to note that not all metallic green or copper beetles are Japanese beetles.
To make sure you are dealing with these pests, you will need to check their undersides, white turfs under the wing covers, and an additional tuft at the end of the abdomen.
Keep on reading.
Why Japanese Beetles Are a Problem?
It is important to note that there is a wide smorgasbord of plants that Japanese beetle like to feast on.
Moreover, more than 300 varieties of trees, shrubs, and non-woody plants are the ones they feed on.
During a year with a serious infestation, you may feel as though there is not a plant that these pests will not enjoy.
While individual Japanese beetles are not much of a threat, these insects tend to hatch in large numbers, and when they congregate on a shrub, tree, or other plant, they will quickly defoliate it.
It is important to note that these pests like to run in cycles, some years are almost devoid of beetles, while in other years they are present everywhere.
When you see an infestation in your yard or garden, it is often a very large one that can seriously damage large numbers of plants.
Their sheer number can make it hard to eliminate them, however, there are certain steps you can take to control and prevent them.
Learn more about Beetle Insects: How to Control Them here.
What do they look like?
Before you begin your battle with Japanese beetle, it is important that you recognize them.
These insects tend to have an iridescent green head and thorax which is the part of the body right behind the head.
Moreover, they are glossy, copper-brown wing coverings that look almost metallic.
It is important to note that one of the biggest giveaways that you are looking for in these beetles is the small fuzzy patches on both sides of their abdomen.
A number of look-alike beetles also tend to have shiny metallic bodies, but they do not have white spots.
Furthermore, Japanese beetles skeletonize leaves by eating the tissue between the veins, so if you tend to see ragged, lacy-looking foliage, that is another sign that you are dealing with them.
The larvae are also known as white grub.
They can cause brown, dead patches in the lawn that will pull up easily, just like a rug.
When to Look for Japanese Beetles?
You will need to start watching for Japanese beetle in May or June and continue to look for them into August.
They are often actively feeding in the morning and late evening.
Moreover, they tend to be most active when temperatures are over 85 degrees Fahrenheit and the air tends to be still.
So make sure to keep an eye out for new beetles coming into your yard during these conditions.
You may not see them on cool, rainy days, but do not think that they are gone.
A warm, sunny day will often bring a resurgence.
It is often a good idea to check for them regularly and control them as soon as possible before they get out of hand.
However, you may notice that their population tends to explode in some years, no matter what you do, and in other years, they are not as high in numbers.
Before getting started
It is important to note that beetles tend to go through four stages of development.
It is also imperative to know that when passing through each stage in your climate as control methods are also different for each stage.
The life stages of the Japanese beetle are:
Egg: The mature beetles tend to lay small, oval, white eggs in the soil.
In case the moisture is enough, the eggs will absorb it and will enlarge, becoming rounder as they do.
Larvae: This one is a white grub that is familiar and damaging to your lawn.
Moreover, it is important to note that the larvae of the Japanese beetle are v-shaped series of bristles on their raster, i.e. the underside of the tip of the abdomen.
The grubs tend to grow in length as they will feed and mature.
Pupae: The pupae stage is where the grubs will begin to transform into a beetle.
Japanese beetle pupae tend to start as cream-colored and then age to a reddish-brown.
Adult Beetle: The adult beetle tends to be less than 1/2 inch long and their shell is shiny, metallic green.
Moreover, adults tend to emerge from the ground between May and June, depending on the area you live in.
They tend to live for about 30 to 50 days during which they will feed and reproduce.
It is important to note that when the first beetle emerges from the ground, it will immediately look for suitable plants and begin feeding.
They will also send out an odor known as a congregation pheromone to signal later emerging beetles where to go and mating will begin soon after.
The female beetle will feed on plants for a couple of days, then burrow into the soil to lay eggs.
Shortly after, they will return to feeding and mating and will begin the cycle all over.
By the end of the season, each female Japanese beetle will have laid about 50 eggs.
It is important to note that eggs tend to develop at different rates in different soil temperatures, developing most fast in warm soils of about 80 to 90 degrees Fahrenheit.
When the soil conditions and temperature is ideal for eggs to hatch, you can expect an infestation of lawn grubs to follow shortly, with large numbers of beetle to appear in the following year.
Once these eggs develop into larvae, they will move toward the soil and start feeding on roots and organic matter.
In large numbers, these grubs can cause severe damage to your lawn, and in some cases, even kill off large areas.
This is why grub control is often applied in late summer to fall.
You need to remember that you will have to apply pesticides while the grubs are feeding on the grassroots.
As the soil cools and the grubs will mature, they tend to move back down deeper into the soil for winter.
They will then stay there until the soil warms in the spring, at which time they will burrow back up toward the surface where they will pupate and eventually emerge as adults.
The cycle now begins all over.
When to Control Japanese Beetle
The proper time to control this pest will depend on what stage of the lifecycle of the beetle you are trying to attack.
Hand-picking or spraying them with chemical or natural pesticides should be done while the beetles are actively feeding on your plants.
It is a period that lasts for roughly a month in late May, June, or July.
Attacking the larvae stage, and the grubs is normally to be done in late summer to fall when the grubs are maturing and moving upward to feed on the roots of the plants.
Moreover, it is possible to get rid of these pests entirely.
More tend to fly in as the current crop kill and there are not many natural controls for adult Japanese beetles.
It is important to note that birds are not partial to them, and though some predatory wasps and flies are imported, their population is not large enough to control them.
Controlling this pest will need you to use one or several hands-on methods.
It is important to bear in mind that the adult Japanese beetle is only around for a while over a month, so do not reach for harsh chemicals unless they tend to become a serious problem.
Warning: A word of caution about the pheromone beetle traps.
They tend to attract beetles, and you will probably wind up with more beetles in your yard than before.
The main intention of the trap was to track when and how many of these were in your area, not as a means of eradication.
What equipment you will need?
Equipment / Tools
For Handpicking method
For Insecticidal Soap & Pesticide Method
- Garden sprayer
For Grubicide Method
- Broadcast spreader
For Milky Spore/Nematode Method
- Garden sprayer
- Garden hose
For Handpicking Method
- Dish soap
For Insecticidal Soap Method
- Insecticidal soap or oil
For Pesticide Method
- Pyrethrin-based insecticide
For Grubicide Method
- Granular grubicide
For Milky Spore/Nematode Method
- Milky spore or nemetode solution
How to remove Japanese beetles by Hand?
The most effective natural control is to remove these beetles from your plants by hand.
You will need to:
1# Create a Solution of Soap and Water: You will need to mix soap and water into a jar and bring this mixture into the garden.
2# Crush Beetles between your fingers: It is important to note that some gardeners tend to crush the beetles between their fingers.
So you can also go down this route if you are not squeamish.
But if you are, you can jump onto the next step.
3# Place Beetles in Soapy Jar: Most tend to brush the beetles off the plants and into the jar of water mixed with dish soap.
This is where the beetles will quickly drown.
It is important to note that the Japanese beetle often feeds in groups starting at the top of the plants, so it is often easy to fill a jar with them.
However, you will need to do this every few days for the month or so that this infestation lasts.
Killing Japanese Beetle with Insecticidal Soap
Insecticidal soaps can help kill Japanese beetle only if you spray them directly on the beetle.
It is important to note that this does not have a residual effect.
This means that when you do not spray on the beetles directly, they will not be harmed.
However, insecticidal soap may also kill other helpful insects like ladybugs.
Any variety of synthetic pesticides can help kill Japanese beetle, however, to be effective, you will need to spray it in large volumes.
It is important to note that it will at the same time kill other insects, as well as pollute the surrounding.
A much better choice is to use neem oil or a pesticide that contains pyrethrin.
Pyrethrin is a biodegradable that is derived from chrysanthemums.
Moreover, pyrethrin insecticide should still be applied selectively, directly on beetles, as it will also kill other insects.
However, this substance does not have a residual effect on the environment and is one of the safest pesticides you can make use of.
Using Grubicides for Long-Term Control
It is important to note that a long-term approach to control the Japanese Beetle is to attack them at the source.
This includes attacking them in the ground where the beetle larvae or grubs tend to feed and mature.
You will normally need to do it by applying a granular gurbicide to lawns in late summer or fall.
This is when the grubs are moving up into the root zone to feed.
Moreover, grub baits are somewhat controversial as they are synthetic chemicals.
However, most of them are classified as only ‘mildly toxic’ by the EPA.
With careful application following the label instructions exactly, this is relatively a safe chemical pesticide.
Grub baits are fairly selective pesticides that tend to affect a number of lawn-damaging beetles and grubs that tend to have less impact on earthworms and other beneficial organisms.
Make sure that you avoid any product that consists of Sevin, as this can kill earthworms and other beneficial organisms.
Tip: If you tend to have repeated intense infestations of these beetles, it is important to check the soil in late summer to see if you have a large group population.
You will need to lift a 1-square-foot section of turf and if there are more than a dozen grubs in this small area, you will need to consider treating your lawn with some type of grub control.
Make sure to remember that not every garden with Japanese beetle problems has a lawn full of grubs.
Moreover, the beetles can hatch in the lawn of your neighbor and find your tasty garden with little effort.
Using Milky Spores and Nematodes
Two natural organisms tend to be very effective at controlling the larvae of these beetles, though it can take a number of years to fully enjoy the benefits.
Milky spores are a natural live organism, Bacillus popilliae that you can apply to the lawn.
Once grubs are infected, they will die within 7 to 21 days and the organisms will multiply and spread through the soil as the dead grub decompose.
Once they establish in the soil, milky spores can protect against these beetles for more than 20 years.
However, it can take as long as 5 years in colder climates for the spores to become thoroughly established.
On the other hand, nematodes are tiny microscopic worms that are found in the soil.
Some types tend to be harmful to the plants, however, the types you can commonly use for Japanese control Steinernema spp. are the ones that target beetle grubs.
Moreover, these nematodes can be killed by direct sunlight, so you will need to apply them on a cloudy day or as night is falling.
Make sure to water them in, as this will assist their passage into the soil.
You can apply both milky spores and nematodes at the same time.
They tend to make a very effective long-term solution to lawn grub and Japanese beetle problems.
Tips for Controlling Japanese Beetles
It is important to note that the presence of Japanese beetle can also be accompanied by the presence of moles ruining your lawn.
The reason is that moles tend to arrive to feed on grubs under the ground.
Controlling grubs, can, therefore, not only eliminate Japanese beetles but also get rid of the mole problem.
Moreover, when the Japanese beetle is an ongoing problem, you may want to consider planting your landscape with plants that tend to be less attractive to them.
Some plants to consider are arborvitae, boxwood, dogwood, firs, hemlock, holly, junipers, lilac, magnolia, oaks, pines, redbud, red maple, and rhododendron