Japanese beetles are extremely destructive garden pests, and they’ve become a major problem for many. In this post, you’ll learn everything you need to know about them, including their life cycle, what they eat, and the damage they cause. Then I’ll show you tons of organic methods you can use to control Japanese beetles.
If you live in an area where Japanese beetles are present, you know first hand just how destructive they can be. It’s very disheartening!
I remember the first time I saw a Japanese beetle in my garden. I actually thought it was kinda pretty (I know, crazy right!?!).
But over the course of 2-3 years, the population exploded, and they quickly became a HUGE pest here in Minnesota. Now I see thousands of them in my garden every summer. Thousands! They are completely out of control.
If you don’t have them in your garden yet, you’re lucky. Fighting them can be extremely frustrating, and it’s pretty much impossible to get rid of Japanese beetles completely.
But it’s not all gloom and doom. There are tons of ways to control Japanese beetles, and prevent major damage to your garden.
Here’s what you’ll find in this guide to Japanese beetle control…
- What Are Japanese Beetles?
- What Do They Look Like?
- Japanese Beetle Life Cycle
- What Do They Eat?
- Damage To Plants
- How To Control Them Organically
- Organic Treatment Methods
- How To Prevent Japanese Beetles
- Does Bacillus thuringiensis kill Japanese beetles?
- How long do Japanese beetles live?
- Why do Japanese beetles sit on each other?
- Can Japanese beetles swim?
- What eats Japanese beetles?
- What time of day do Japanese beetles feed?
- How do you get rid of Japanese beetles permanently?
- Do Japanese beetles bite or sting?
What Are Japanese Beetles?
Japanese beetles are extremely destructive garden pests that were introduced into the United States in the early 1900’s. They are native to Japan (hence the name), where they aren’t considered a pest. But, they’re an invasive species here in the US.
Over the last century, they have become a widespread problem in many states in the eastern and midwestern US, and in areas of southeast Canada. They are slowly making their way to the western parts of North America, so be prepared.
What Do Japanese Beetles Look Like?
Adult Japanese beetles are oval-shaped iridescent bugs. They have a bronze-colored body and a green head, with fine white hairs on their undersides.
There are five white tufts of hair along both sides of their body, which look like dots from the top, or lines from the side. The adults are usually about 1/2 inch long, but can be smaller. They can fly, and are very active during the day.
In their larval stage, Japanese beetles are C shaped white grub worms that live underground. The grubs are about a 1/2 inch long or so, and have a white/cream colored body with a tan/orange head.
Japanese beetle grubs also have six creepy looking legs on the top of their body, and a green-brown colored tail end.
Japanese Beetle Life Cycle
There are four stages to the Japanese beetle lifecycle: egg, larvae (aka grubs), pupa, and adult. Interestingly enough, Japanese beetles spend most of their life underground.
The female beetles lay eggs in the soil, where the larvae hatches a couple weeks later. The larvae feed and grow until the soil begins to cool in the fall. Then they go deeper into the ground, where they hibernate for the winter.
In the spring, the grubs make their way back to the top of the soil, where they feed on the roots of grasses and other plants until they’re large enough to pupate.
It takes a few weeks for them to pupate into adults, and then they emerge from the ground to start feeding on our gardens.
Adult Japanese beetles beetles start emerging in late June/early July here in Minnesota. But it could be earlier depending on where you live.
At least we have one thing to be thankful for… there is only one generation of Japanese beetles per year. Whew!
When Do Japanese Beetles Go Away?
The adult Japanese beetle lifespan isn’t very long, they only live for about two months. But they can do a LOT of damage in that short amount of time, as many of us know first hand!
What Do Japanese Beetles Eat?
In order to effectively control Japanese beetles, it’s important to know what they eat. Unfortunately, they feed on tons of different types of plants and trees, which is what makes them such a major pest. But they do favor some over others.
This extremely destructive pest does double damage. Not only are the beetles a huge pest, but the larvae are too. Japanese beetle grubs feed on the roots of lawns and other plants, which can damage or ultimately kill them.
Though they can eat pretty much any type of plant, here’s a list of the ones they love the best in my garden. There may be others on your list, depending on where you live…
- canna lilies
- linden tree (they also love fruit trees like apple and peach)
Japanese Beetle Damage To Plants
Japanese beetles damage plants by eating holes in the flowers and leaves. They can skeletonize the foliage, and destroy the flowers very quickly. A large population can decimate a small plant in a short time.
The good news is that they mainly feed on leaves and flowers, and they very rarely kill a plant. As ugly as it is, mature plants and trees can usually withstand Japanese beetle damage without any long-term effects.
Grub damage isn’t usually as severe or noticeable as with the adults. They mostly feed on the roots of grasses, which can cause areas of your lawn to turn brown and die.
However, moles and other animals love eating grubs, and will dig them up to feast. And they can cause much worse damage to your lawn than the grubs do.
How To Control Japanese Beetles Organically
The key to controlling Japanese beetles and prevent an infestation is to get on top of the problem right away. Once they start feeding, they will attract more beetles. So the sooner you get on it, the better.
But before you start planning your counter-attack, please try to remember that the beetles usually only cause cosmetic damage to plants, and rarely kill them. So, there is no reason to reach for toxic chemical pesticide to get rid of Japanese beetles.
Pesticides don’t discriminate, and they can kill all types of insects. Including bees, butterflies, and many other beneficial bugs. So please stick to using organic methods instead.
Organic Japanese Beetle Treatment Methods
Unfortunately, getting rid of Japanese beetles completely isn’t a realistic goal. They can fly a very long distance. So, if you live in an area where they’re present, it’s pretty much impossible to eliminate them from your garden.
But the good news is that you can greatly reduce the amount of damage they cause to your plants. And there are many, many different ways to control Japanese beetles organically…
The best way to get rid of Japanese beetles is to remove them from the plants. Simply hand pick them off, and drop them into a bucket of soapy water to kill them. Gross, I know! But don’t worry, you’ll get used to it.
By the way, don’t just use water in your bucket, make sure to put soap in there too. The soap will kill Japanese beetles quickly. Otherwise, they can swim for a really, really long time – like days. It’s creepy! And disgusting.
I’ve tried a few different types of soap in my bucket, and I love Dr. Bronner’s Baby Mild liquid soap the best. It kills the beetles faster than other soaps I have used, which means there’s no way any of them will escape my bucket!
The best time to hand pick them is early in the morning, or in the evening. They aren’t as active during these times of the day. I don’t know about you, but I can’t stand doing it during the day when they’re buzzing around and flying at me – EEK!
Hand picking the Japanese beetles sounds easier than it is because sometimes they hold on tight to the plant and won’t let go.
Either that, or they will drop off the plant as soon as you disturb it, so you have to be quick with the bucket. And don’t stand directly under the beetles either… just trust me on this one (that’s a story for another day).
But don’t let me scare you, hand picking them is pretty easy once you get the hang of it. Plus, it’s definitely satisfying to see all those nasty things floating in the bucket at the end of the day.
You can try sprinkling Japanese beetles with diatomaceous earth to kill them. Diatomaceous earth (DE) is an all-natural powder made from hard-shelled organisms.
It gets under the beetles shells as they move around, which cuts them up, and eventually kills them (sounds bad I know, but it’s way better than using chemicals!).
DE will be most effective when you apply it directly on the beetles, rather than just spreading it everywhere. You could also try using eggshell powder in a similar way.
The soap will kill some of them on contact, and the rest will be stunned and easier to hand pick. Insecticidal soap doesn’t have any type of residual effect though, so you have to spray it directly on the bugs.
The best time of day to spray Japanese beetles is in the morning or evening, when they aren’t as active. Don’t spray plant in the middle of the day because the hot sun could cause damage.
Beneficial nematodes are a natural way of controlling grub worms in the soil. These are tiny organisms that feed on grubs, and kill them before they can emerge as adults.
For best results, apply beneficial nematodes in the fall when the grubs are young, and closest the surface of the soil. Learn how to use beneficial nematodes here.
Harmless to beneficial bugs, milky spore is a naturally occurring bacteria that infects the grubs when they eat it, and eventually kills them.
The downfall is that it can take 2-3 years for this method to be effective. But once active, milky spores last in the soil for several years.
Pheromone traps are another great option for controlling Japanese beetles without spraying harmful pesticides. They are completely non-toxic, and harmless to other bugs.
The traps work by attracting the adults with pheromones and other scents they can’t resist. They fly into the trap, but can’t get back out. Read more about how to use Japanese beetle traps here.
How To Prevent Japanese Beetles
One of the easiest ways to control Japanese beetles is to prevent them in the first place. There are a few methods you could try to prevent them from damaging your plants…
Protect Your Plants
Try covering your prized plants and flowers to keep them from being destroyed. This works great for plants that don’t need to be pollinated by bees.
Use row covers, inexpensive tulle fabric, or garden fabric to keep Japanese beetles off plants. Just be sure to secure it around the bottom, otherwise the beetles will find their way in. I use clothes pins to hold my fabric in place, and secure the bottoms.
Try Repellent Plants
There are a few plants that are said to repel Japanese beetles, including tansy, rue, and garlic. So try interplanting them with those that the beetles love the best, and see if they help to deter them.
Grow Plants They Won’t Eat
Like I mentioned above, there are plants that they tend to favor over others. So, if you’re tired of fighting to control Japanese beetles in your garden, then try planting stuff they don’t like instead. Here’s a list of things to try…
- ash trees
- maple trees
- burning bush
- oak trees
There are probably many more that you can add to this list, depending on where you live. But these are just a few common ones to get you started.
In this section, I will answer some of the most frequently asked questions about Japanese beetles. If you still have a question after reading through this post and these FAQs, ask it in the comments below.
How long do Japanese beetles live?
Adult Japanese beetles only live for about 6-8 weeks. But the grubs live underground for the rest of the year (or about 10 months).
Does Bacillus thuringiensis kill Japanese beetles?
Bacillus thuringiensis (BT) is primarily used for killing caterpillars and worms that feed on plants above ground. Though it may work on Japanese beetles too, the methods I have listed above are much more effective.
Why do Japanese beetles sit on each other?
Ehem… that’s because they are mating with each other. Yep, they have no shame.
Can Japanese beetles swim?
Yes, and they can swim for a very long time. So when hand-picking, it’s a good idea to add some liquid soap to the water, which will kill them very quickly.
What eats Japanese beetles?
Many types of birds feed on Japanese beetles, including chickens. There are also some types of beneficial parasitic wasps, and other insects that feed on either the grubs or adult beetles.
What time of day do Japanese beetles feed?
They are most active during middle of the day, especially when it’s hot and sunny. They usually start feeding in the late morning, after the dew has dried, and the temperature has warmed up.
How do you get rid of Japanese beetles permanently?
Like I mentioned above, it’s pretty much impossible to get rid of Japanese beetles permanently. So, even if you were able to eliminate them from your yard, more of them can fly in from anywhere. Instead, focus on organic Japanese beetle control methods, as described above.
Do Japanese beetles bite or sting?
No, thankfully! They’re harmless to humans and pets, and they do not bite or sting.
Working to control Japanese beetles in your garden can be very frustrating. But with so many organic options, there’s no reason to use chemical pesticides. Just remember, you’re not going to be able to get rid of Japanese beetles all together. So make controlling them your goal, and you’ll be much less stressed out.
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Leave a comment below and tell us how you control Japanese beetles in your garden organically.