Japanese beetles are known for their destructive nature on plants and crops, but many wonder if these pests also bite humans. The primary concern with these beetles involves damage to plant life, as they feed on the foliage and fruits of numerous plant species. Originally found in the United States in 1916, Japanese beetles have since spread throughout most of the country.
While their impact on plants is significant, Japanese beetles are not typically considered a threat to humans. Bites from these beetles are rare, but they can occur under certain circumstances.
Understanding Japanese Beetles
Japanese beetles are small insects with metallic green bodies and copper-colored backs. Their tan wings make them easily recognizable. These beetles are approximately 5-7 mm wide and 8-11 mm long source.
Japanese beetles are known for their voracious feeding habits. They feed on more than 300 types of plants, causing significant damage to lawns, golf courses, and crops source. Their destructive nature can be attributed to the following characteristics:
- Both adults and larvae are aggressive feeders
- Adults are attracted to more plants, leading to further infestations
- Larvae feed on grass roots, causing damage to turf and landscape plants
These beetles’ feeding habits can cause foliage and flowers to become skeletonized or reduced to thin, lace-like structures. The presence of beetles on a plant usually attracts more beetles, making control more difficult source. To protect high valued plants, some methods can be employed, such as using fine netted material, removing beetles physically before they multiply, and applying biological or chemical controls.
Impact on Plants and Lawns
Japanese beetles are known to attack the foliage, flowers, or fruits of over 300 different ornamental and agricultural plants. Some common examples include:
Damage to Leaves and Roots
These beetles feed on plant leaves, creating a skeletonized appearance as they consume the tissue between leaf veins. Their larval stage, known as grubs, feed on grass roots, potentially causing significant damage to lawns.
Dying Grass and Brown Patches
Grub-damaged turf often results in brown and dying grass, as the grubs effectively sever the connection between the plant and the soil. This can create loose patches of dead grass that can be easily pulled from the soil.
|Damage Caused by Japanese Beetles
|Roses, Grapes, Raspberries, Beans
|Roots & Lawns
|Brown patches, dying grass
Do Japanese Beetles Bite
Mandibles and Bites
Japanese beetles have mandibles that they use to chew on plant foliage. However, these mandibles are not strong enough to penetrate human skin, so they do not pose a risk of biting people.
Some people might feel a slight pinprick sensation if a Japanese beetle lands on them, but this sensation is not due to a bite. It may just be the beetle’s legs or other body parts brushing against the skin.
Distinguishing from Asian Lady Beetles
Japanese beetles should not be confused with Asian lady beetles which can occasionally bite if threatened. Here’s a comparison table to help differentiate these insects:
|Asian Lady Beetle
|1/3 to 1/2 inch
|1/4 to 1/3 inch
|Metallic green/blue, coppery brown wing covers
|Orange, red, or yellow with black spots
|Gardens, lawns, trees
|Gardens, crops, homes during winter months
Do remember the following points:
- Japanese beetles have mandibles not strong enough to bite humans.
- They may cause a pinprick sensation but not from biting.
- Asian lady beetles, unlike Japanese beetles, can bite occasionally.
Preventing Japanese Beetle Damage
Japanese beetles can cause significant damage to plants, including skeletonized leaves. To prevent this:
- Remove beetles early. Their presence attracts more beetles to the plant.
- Shake beetles off in the morning when they’re sluggish.
- Place beetles in a bucket of soapy water to kill them.
- Use cheesecloth or a fine net to cover high-value plants.
For example, covering rose bushes with a fine net can help protect them from beetles.
Maintaining Healthy Lawns
Japanese beetles also contribute to dying grass by feeding on grass roots. To maintain a healthy lawn:
- Monitor for beetle larvae.
- Implement proper watering and fertilization routines.
- Aerate the soil to promote healthy root growth.
For instance, aerating the lawn in the spring and fall can help prevent beetle infestations.
Comparison Table: Protecting Plants vs. Maintaining Lawns
|Preserves plant health and beauty
|Requires daily monitoring and manual removal
|Prevents grass from dying
|May require professional lawn aeration
In summary, preventing Japanese beetle damage involves both protecting plants and maintaining healthy lawns. By following these tips, you can minimize beetle infestations and maintain a beautiful garden.
Over the years, our website, whatsthatbug.com has received hundreds of letters and some interesting images asking us about these insects. Scroll down to have a look at some of them.
Letter 1 – Japanese Beetles
Please help me identify this bug
I have been searching for some time now and cannot figure out what these bugs are. They have been eating my grape leaves and raspberry leaves and killing the plants. Any help as to what it is or how to get rid of them would be extremely helpful. Thanks in advance,
Though you did not provide us with a location, we think your photo will help our readership identify the Japanese Beetle, one of the most destructive invasive exotic species on American soil.
Letter 2 – Japanese Beetles
June 24, 2010
Hi Daniel, You asked for images of Japanese Beetles. I had a few but none were very good, so I took some more today. Not really pleased with these either, don’t know why but my camera doesn’t seem to focus on them very well. Perhaps they are clear enough for an ID. I never cropped one very close to show the “lace leaf” you were talking about, this is a grape leaf. I hope you are able to use these. Thank you and have a great day.
North Middle Tennessee
Hi again Richard,
With all due respect, if you were our photography student, we would tell you that you are nuts. This photo has everything. We especially love that it shows the leaf damage caused by the beetle, which our mom in Ohio compares to lace doilies. The two pairs of beetles on the right appear to be mating. While the focus on the right of the image is not critically sharp, it is more than acceptable especially considering the detail in the Japanese Beetle in the upper left. We also appreciate that you managed to send us photos of all the insects we saw in Ohio earlier in the week that we lamented not having had a camera so we could take our own: The Question Mark, Great Spangled Fritillary, and Firefly as well as the Japanese Beetles.
Letter 3 – Japanese Beetles
Location: central ohio
August 1, 2014 12:46 pm
Central Ohio area. Eating tree leaves. Summer:-) please help! Thank you.
These are invasive, exotic Japanese Beetles and they were accidentally introduced into North America about 100 years ago. Most eastern gardeners are familiar with Japanese Beetles because they eat the leaves and blossoms of over 100 different cultivated and ornamental plants, including roses.
Thank you very much. They are destroying my trees! I thought that might be what they were, but was unsure. Thanks again
Letter 4 – Japanese Beetles
Location: Central WI
July 12, 2016 2:02 pm
What is this bug? We are camping and it is on what we think might be an Ash tree but not sure! Thank you!
These invasive, exotic Japanese Beetles are turning those leaves into what mom calls “lace doilies.”
Letter 5 – Japanese Beetles: Bumper Crop Year
Last year I promised you a picture of a Japanese Beetle, as they normally frequent my garden. Well, last year there were none. This year I think I caught a Japanese Beetle family reunion. The photos were taken in Northwest Ohio on 7/6/2006.
Thank you for sending in this wonderful photo of the scourge of eastern gardeners. Mom currently has Japanese Beetle problems with her roses and primroses near Youngstown Ohio.
Letter 6 – Japanese Beetles in Canada
Subject: Vine munching beetle
Location: Southern Ontario, GTA
July 4, 2014 7:59 am
The vines that cover my back yard have been starting to die, I thought it was the neighbours until I went out side today.
I found over eight pairs of beetles mating and eating the vines in the same area.
It seems that while the female eats the leaf under neither the male gets on top to mait.
It has been only a few days and the beetles have decimated the one vine although this is the first time they have been visible.
The hard shell is a redish brown while the sides have slight stripping.
Thank you for the consideration
Signature: Backyard Beetle Babe
Hi Backyard Beetle Babe,
The invasive, exotic Japanese Beetles in your image are doing what they are best known for doing: eating and mating. Japanese Beetles have been in North America for nearly 100 years, and they are known to feed on hundreds of different cultivated and ornamental plants, hence they are well known to and loathed by most gardeners in the eastern part of North America.
Thank you so much for identifying my bug!!!!
Letter 7 – Japanese Beetles eat Chinese Elm: 100 Year Anniversary of Accidental Introduction
Subject: Flying Beetle ?
Location: Inver Grove Heights MN
July 4, 2016 3:54 pm
Found on cut Chinese Elm
Signature: Jeff G
These are invasive, exotic Japanese Beetles, an introduced species that has been plaguing North American gardeners for the past century. According to BugGuide: “The original U.S. population was detected in New Jersey in 1916, having been introduced from Japan” which makes 2016 the 100th Anniversary of their introduction. BugGuide also notes: “Larvae feed on roots of many plants. Adults feed on foliage, flowers and fruits of various plants.” Mom, who is an avid gardener, refers to the feeding pattern, which is evident in your image, as creating “lace doilies” from the leaves of plants.
Letter 8 – Japanese Beetles eating and mating
Subject: Chrome coloured beetle
Location: Ontario Canada on Lake Huron
August 4, 2017 4:34 pm
Not exactly sure what these are so I’m curious but I was taking a small hike with a friend and my dogs on the tiger Dunlop trail in Goderich Ontario. It’s a beach town but the parts of the trail we started to see them wasn’t close to water. We saw so many of these guys EVERYWHERE! They seemed as if they were decimating all of the plants as well? Seemed as if the concentration was mostly the wild fruit plants like the raspberries and grapes. It also seemed like they were always also in groups together like they are in the photo I took. Goderich Ontario is in Canada on Lake Huron. I think it’s classified as southwestern Ontario but I’m not certain.
Signature: Thora Bilcke
These are Japanese Beetles, an Invasive Exotic species first introduced to North America over a hundred years ago. As you observed, they feed on many different plants and they represent a scourge to many home gardeners, especially those with a fondness for growing roses.
Hmm that is interesting. This is the first year I’ve ever seen them. Thank you!!
Letter 9 – Japanese Beetles make “lace doilies” from grape leaves
Subject: Beetle eating my grape leaves
Geographic location of the bug: SC Kentucky
Time: 05:32 PM EDT
Your letter to the bugman: These beetles showed up almost over night and are eating all the leaves of what I think are grapes.
How you want your letter signed: Brad Beach
Because they will eat the blossoms and leaves of so many prized garden plants including roses, blackberries and peaches as well as your grape vines, Japanese Beetles are among the most reviled, introduced species that affect home gardeners. According to Featured Creatures: “More than 300 species of plants are known to be host to Japanese beetle.” Your array of images makes for a perfect Japanese Beetle posting, including the image of the mating pair and the documentation of the damage to leaves, which Pearl calls “lace doilies.”
Letter 10 – Japanese Beetles Mating and Eating Raspberries
Subject: What’s this bug?
Geographic location of the bug: Southern Ontario, Canada
Time: 08:35 PM EDT
Your letter to the bugman: Hi bugman. These bugs seems to love my raspberry’s, they also love loving on the leaves(as you can see). Do you know what they are?
How you want your letter signed: Sincerely, Andrew
Let us introduce you to the Japanese Beetle, a species loathed by American gardeners, especially those who grow roses, for over 100 years. According to BugGuide: “earliest record in our area: NJ 1916.”
Letter 11 – Japanese Beetles mating and Syrphid Fly feeding
Bedroom or dining room?
Dear Lisa Anne and Daniel,
"Must You Do That While I’m Eating?" Think of this bug love episode as nature’s own shunga, especially as its main characters are Japanese beetles. Isn’t it bizarre that the bee-mimic hover fly (in addition to being there in the first place) is actually HOLDING this flower’s stamen while it slurps? Taken in Pennsylvania on a July afternoon in 2001.
Jim & Sandy
Hi Jim and Sandy,
Thank you for this humorous image that will get archived to numerous pages: Beetles 11, Flies 3 and Bug Love 4.
Letter 12 – Japanese Beetles Procreating
Hello Again, I hope all is well. This is a very common insect at the conservation area. The shell is a beautiful copper colour – the photo does not do it justice. Today it was extremely hot and humid and after a brief rain all the insects – moths, butterflies, and everything else that crawls or flies was mating!! Take Care,
Though your photograph is lovely, it will have rose growers cringing. The Japanese Beetle, Popillia japonica, was first discovered in New Jersey in 1916, and the introduced species quickly spread throughout the eastern states. The grubs live underground in lawns where they eat grass roots, and adults emerge in mid summer to devour roses, fuschias, and other ornamental blooms.
Letter 13 – Japanese Beetles ravage garden in Canada
A garden feast
Location: Toronto, Ontario, Canada
July 23, 2011 6:11 pm
We moved into our current home late last summer, and were disappointed to see all of the apples on our apple tree eaten, or on the ground full of holes.
The same thing is happening this year, and on top of that, many of the flowers we planted are being eaten! Oh the humanity!
Please help identify this culprit…Definitely not a helpful bug.
Signature: Vince S.
You are being plagued by one of the most well known invasive exotic species to have been introduced to North America, the Japanese Beetle. The beetle is so well known because it was originally introduced to North America on nursery stock that entered the U.S. in New Jersey. Since that time, it has spread across the country and despite all attempts to eradicate it, the Japanese Beetle populations show no sign of being under control. Numerous products are on the market, including Japanese Beetle traps. Because Japanese Beetles are relatively indiscriminate eaters, they will consume hundreds of different cultivated plants. When the hoards have defoliated one plant, they will just move to another species. They are especially fond of roses, much to the chagrin of many home gardeners. Regarding your apples, we are not fully convinced that the Japanese Beetles are feeding upon them, and if they are, we suspect they are only doing peripheral damage. While they will feed on the leaves of the apple tree, the damage you describe does not sound like Japanese Beetle damage. We suspect birds might be picking at your apples while the beetles feed on the foliage. It is also worth noting, that according to BugGuide: “Adult females lay eggs in soil June through early fall. Grubs feed on roots until hibernating underground (4-8″ deep) as third instar larvae when cool weather comes.” It looks like there is mating activity going on in your photo of the apple tree.
Letter 14 – Kinky Japanese Beetles
I saw your page for mating bugs and thought I would give you an even better (and funnier) Japanese Beetle picture. I call this….Beetle Orgy!
Your photo speaks for itself. We especially like the voyeur. Your photo could compromise our recent good reputation with Elementary Schools as well as religious fanatics.