If you have a garden and live on the east or west coast, you have almost certainly encountered this scenario before. You pop out to your garden one sunny, warm day and then you see it. That brown, metallic glint in the light. A flutter of movement. And then you know for sure…
Japanese beetles! They are back, and even as the thought crosses your mind they are hungrily chewing the leaves and fruits of your plants down to husks, time and time again, year after year, and there is seemingly nothing you can do about it to stop them.
Luckily, that last sentiment just isn’t true. What is true is that these sneaky scarabs can definitely devastate your plants, but armed with the right knowledge and the right supplies you have a better than average chance of successfully fighting back.
This article will tell you everything you need to know about getting rid of Japanese beetles for good.
Table of Contents
What are We Dealing With?
Japanese beetles, scientific name: Popillia japonica are a species of beetle, scarabs that first arrived in the United States in 1916.
They have since spread to almost every state east of the Mississippi River, as well as some parts west of it at an increasing rate yearly. Most recently, they are confirmed in formerly beetle-free Wyoming just in 2020.
These rapacious critters are about 1/2 an inch long and are quite beautiful if you are into entomology.
They have a metallic and iridescent emerald green head and thorax, and a shiny metallic bronze “body” (actually their wing covers) with six banded tufts of white hair along their sides.
They have six legs with grasping hooks and spines, and two long, fronded antennae that they use to sense their environment.
If you have ever had one land on your finger or clothes, you know they have a quite a grip!
Adults emerge from the ground in late May or early June, mate, and then start to feed on the leaves of plants and some fruit with a voracious appetite.
After about 2-4 weeks of gorging themselves, they burrow back into the soil to lay their eggs, starting the cycle anew.
As the larva (white grubs) hatch underground they spend 10 months eating the roots of grasses, weakening and killing them, before pupating and emerging as adults the following summer.
How Did Japanese Beetles Get Here?
The first recorded sighting of Japanese beetles in the United States was in 1916, in a nursery in Riverton, New Jersey.
It is theorized that the beetles were accidentally introduced through a cargo of plants (long theorized to be irises) from Japan, as this was a common import at the time.
The larvae would have survived the voyage hidden among the plants’ roots, and then emerged as adults in the new country.
From that single nursery, the beetles have slowly but surely spread across the country via a combination of their own movements and human assistance.
Now, in the 21st century, we seemingly will never be free of the things.
Why are Japanese Beetles a Problem?
Japanese beetles are a problem because they cause a great deal of damage to both crops and ornamental plants.
The adults feed on more than 300 species of plants, including (but certainly not limited to) grapes, raspberries, strawberries, apples, pears, asparagus, lima beans, snap beans, potatoes, roses, cherries, and plums.
In fact, these little buggers are so destructive that the United States Department of Agriculture lists them as one of the most serious pests to crops in the country.
The damage caused by Japanese beetle adults takes two forms: defoliation and fruit damage.
When they eat leaves, they skeletonize them by chewing the tissue between the veins, leaving the larger veins intact.
This type of damage is most common on broad-leafed plants but can affect all vegetation that is on their menu.
Fruit damage occurs when the beetles chew holes in soft fruits such as raspberries and grapes, ruining them. Though damage to plants overall is mostly cosmetic, serious predation can weaken or kill them.
Worse, the Japanese beetle has no natural predators native to North America- it is an invasive species- so its population has been able to grow unchecked.
They are reasonably strong flyers, and can easily travel several miles in search of food, so they are difficult to contain.
For homesteaders and home gardeners, even a day’s worth of attention from a swarm of Japanese beetles can devastate your plants.
Don’t Sweat It; You Can Beat These Beetles
Now, don’t panic. If you have dealt with these little emerald rascals before you know how bad they can be, you know what you are facing.
If you haven’t, don’t despair, they aren’t as invincible as they might appear at first blush. You can get rid of Japanese beetles, and keep them gone for good. Here’s how:
How Can We Deal With Them?
The time has come to put up or shut up. Now is when we send the beetles packing.
You have options, and any, some, or all of them might be viable ways of dealing with the problem. Consult the following and see which will work best for you.
One of the best ways to deal with Japanese beetle invasions is avoiding having to deal with them at all. You have a couple of options if you want to take this approach.
The first, and one of the best, is to get them while they are young and still in the ground as grubs.
Now, don’t get me wrong. They still cause plenty of damage while they are in their larval stages because they completely obliterate the roots of grasses, causing die-off and soil erosion.
That being said, they typically do less damage when they are in the ground. Happily, you can exploit a specific vulnerability to a certain kind of disease called milky spore, caused by specific bacteria.
This disease is fatal, and can easily wipe out Japanese beetle larvae and mass, but if you want it to work you’ll need to apply the prescribed agent across your lawn and surrounding areas for at least a year for it to be reliably effective.
This is something you should commit to now if you want to include it in your defensive regimen.
And, of course, you can prevent the beetles from reaching your plants by covering them with any number of things, from row covers to fine mesh. You could even use something like plastic sheeting or breathable fabric for the purpose.
It doesn’t even have to fully enclose the plant so long as it will prevent most, or even some, of the insects from reaching the plants on their travels then the overall damage they inflict can be reduced.
This might create complications if you are relying on other pollinators to reach those plants, so timing and a thorough understanding of the life cycle of your plants are important.
However, if you can keep your plants covered for a few weeks, the beetles will move on or die off.
Depending on how squeamish dealing with insects makes you, and how many of these blasted critters you are dealing with, direct intervention and the form of physical removal and extermination might be the best overall option for you, and one with the least possible environmental impact to your plants and surrounding area.
Simply, all you need to do is find the Little critters wherever they land in congregate, usually on targeted plants, and then remove them prior to crushing them or dumping them into a bucket of soapy water which will kill them.
Now, in the cases of major outbreaks or migrations, you might be spending hours out in your garden or elsewhere on your property picking off these beetles one by one.
It is my numbing work, and if you are afraid of insects pretty harrowing. But you shouldn’t underestimate how effective it can be.
Every beetle that you pick off is one less that will be chewing on your leaves and one less that is able to breed and reproduce. With diligence, you can significantly reduce the number of beetles in your immediate area, and if you can get your neighbors and relatives in on a campaign of direct intervention you might even be able to significantly reduce the number of beetles in your immediate locale.
One important thing that battlers of these Beatles usually overlook is the necessity of cleaning up after they have managed to chew up one or more of your plants. What you probably don’t know is that damaged leaves, particularly those damaged by Japanese beetles, emit an odor that is detectable by other beetles that will subsequently home in on it.
For this reason, you should make it a point to prune off any damaged leaves and fruit left behind after their efforts and your efforts to remove the offenders.
By employing removal and repair strategies in this way you can produce a synergistic effect that will deplete the number of beetles in the area and to make it harder for the others to find their way to their erstwhile dinner table.
As always, it is possible to poison Japanese beetles just like you would any other insect pest. They are just insects, with a pretty conventional biology compared to others in their genus.
Both pyrethrin and carbaryl-based toxins are effective against them. By treating usually affected plants or likely targets, it is possible to protect them from the predations of these beetles.
However, pesticides and especially wide spectrum, non-specific pesticides in particular always present a serious trade-off: they don’t just kill Japanese beetles or target pests.
Pretty much every insect and many Crustaceans that come into contact with the toxin will be affected and die, and most sadly this includes beneficial, helpful insects too.
Pollinators like bees, wasps, and moths, natural pest killers like ladybugs and dragonflies, and all others in between will all fall prey to your campaign of chemical warfare.
In the cases of truly heinous invasion, pesticides might be your only choice for regaining control, but in my opinion, it is not something that you should do lightly.
Consider Unappealing Plants
You might think it is running the white flag up the pole, but if you have been long suffering underneath the domination of Japanese beetles it might be time to consider a change of plants.
There are many plants that these beetles don’t seem to like very much and generally leave alone.
Such plants might make for acceptable replacements in the case of decorative plants, and in the bargain, you could be saving yourself a ton of time, effort, and grief worrying about the next invasion.
Some plants that Japanese beetles seem to ignore, according to the University of Minnesota, include:
- Japanese maples
- American holly
Of course, this is not an exhaustive list, and you should do your own research to find out what other plants might work in your area.
But it is a good starting point, and by planting these or similar plants you could be making your property a lot less attractive to Japanese beetles in the future.
Try Plant Resistant Varieties of Favorites
If you just can’t stomach the idea of giving up your favorite plant that Japanese beetles love to chew on, then you might want to consider planting a resistant variety.
Some plants have been bred specifically to be less attractive or more difficult for these beetles to damage.
Some such varieties are available among such plants as:
- Asiatic lilies
- Black-eyed Susans
- Blanket flowers
- Butterfly bush
- Mexican sunflowers
- Purple coneflowers
Again, this is not an exhaustive list, and you should consult with your local nursery or garden center to see what varieties might be best suited for your area.
But planting these or similar plants could help you to get the upper hand over these mongrel invaders.
Assuming you aren’t trying to raise award-winning plants or produce, and also assuming that you aren’t dealing with truly massive numbers of beetles, your best bet for dealing with them might be to simply ignore them.
As mentioned, though the damage they cause is certainly unsightly and can ruin fruits and vegetables, particularly soft ones that are easy for them to chew, the damage they call to the plants overall is rarely anything serious.
Assuming that the plant isn’t already sick or stressed, some chewed-up leaves aren’t much to worry about in the grand scheme of things.
Ultimately, you might focus your prevention and interception efforts only on those plants that you want in showroom-ready shape.
These targeted prevention efforts might compound since Japanese beetles are attracted to the presence of other beetles and left to their own devices on certain plants they might congregate there and then move on or die off, leaving your prized plants intact.
Use a Multi-Layer Defense Strategy
Keep in mind that you should employ multiple approaches, where possible, to maximize efficiency.
You might, for example, plant some resistant varieties while also using some of the other methods here to further reduce the population and damage.
You could cover the most vulnerable plants while leaving a badly damaged one to attract beetles for subsequent disposal by hand.
There are all sorts of approaches, and you should spend a little time figuring out how best to implement them in your own particular situation.
But whatever you do, don’t give up! Whatever method or combination of methods you choose, with a little bit of persistence you should be able to get rid of Japanese beetles for good.
What You Shouldn’t Do
If you have already been shopping for solutions against these persistent and colorful pests, you are likely already aware of the presence of specialized Japanese beetle traps.
You are probably also wondering why I neglected to mention such traps as a viable option. There is a good reason for the omission: they do more harm than good!
These traps are designed to attract beetles with a pheromone or scent, and then trap them in a bag or other container. Fair enough, other insect traps work in a similar way.
The problem is that these traps actually attract way more beetles than they catch, and thereby wind up causing more localized devastation.
A University of Kentucky study assessed the viability of said traps and determined that while the beetles did indeed home in on the traps reliably, once they were in the vicinity they would break off and land on nearby plants instead or landing, fatally, in the trap itself.
The study concluded that the nearby area was always worse off than it would be if there were not traps around at all.
Sadly, these attractively priced over-the-counter solutions are anything but. Make sure you stick with my recommendations above and you should come out okay in the coming war!
Biological Controls are Being Trialed, but Their Effectiveness is Uncertain
One “global” option that might prove effective in dispensing with these pests, or at least reducing them to far more manageable numbers, is the introduction of natural predators taken from their home region of Japan.
There are a number of these predators that have been trialed in North America with some success, but their long-term effectiveness is still uncertain. The most common and promising of these predators are two, a fly and a wasp:
- The parasitoid wasp Tiphia vernalis targets the beetles young, capturing and laying eggs on the larva to feed their own young.
- The winsome fly Istocheta aldrichi lays an egg directly on adult beetles, which hatches with fatal consequences.
Gruesome stuff to be sure, but these two competing critters have an undeniable record of success against our nemesis. In fact, significant “native” populations have been established in Minnesota and elsewhere.
Unfortunately, the full story is a little more complicated than that. While both the fly and the wasp might be doing their jobs just fine, it seems like they are not having a significant effect in areas where their populations have had time to build up.
At least, they aren’t so far. In other words, they might not be having much of an impact on a local level in many areas.
Another potential problem with relying on these predators is that they might yet target “good” beetles along with the “bad”.
At the end of the day, we have only introduced two more invasive species to our own ecosystem, and the far-reaching consequences of that are impossible to predict.
So while these biological controls might be a viable solution they come with their own set of risks and uncertainties. Only time will tell.
Do Your Part Against the Beetle Menace
In short, there are a number of potential solutions to the Japanese beetle menace, but it is important to carefully consider the risks and benefits associated with each before making a decision.
The most promising long-term solution seems to be the introduction of natural predators from Japan, although their effectiveness is still uncertain.
In the meantime, avoid using traps that attract more beetles than they catch, as these can actually make things worse.
You can successfully repel Japanese beetles with coverings, resistant plant cultivars, or by disposing of them en masse by hand or with pesticide.
By implementing some of the other suggestions in this article and you should be able to get rid of Japanese beetles for good.
Tom has built and remodeled homes, generated his own electricity, grown his own food and more, all in quest of remaining as independent of society as possible. Now he shares his experiences and hard-earned lessons with readers around the country.