So long Japanese beetles, there's a new sheriff in town!

I let a whole lot of wild plants grow in the food forest this year. All of a sudden I couldn't find any Japanese beetles.

Then I found one... with a robberfly!

You have parked my curiosity.  Is there something that will repel or kill the Japanese Beetle?  What do I need to do?  Currently the only option I have is to use the poison at the base of the tree to kill the beetle.  If there is any natural remedy I would love to try it.

What I did was wonderfully simple. I just let a lot of wild plants grow up in my food forest. I didn't plant any of them, they just came up on their own.

I think that it has provided cover for the robber flies and other predatory insects to ambush their prey, given them shelter from predators, and also gives them a spot to lay their eggs.

They along with other predatory insects were very effective in controlling "pest" insects. I'm really excited to see how it is this coming year, as I expect it to be even better.

Cool!

Michael Fundaro, your fight against the beetles may be hindered by neighbors-- if you are surrounded by a lot of lawn grass, then the larvae are feasting on the grass roots before attacking your plants. There is a natural remedy called "milky spore," but unless neighbors treat also it may be futile.

My food forest is surrounded by large expanses of lawn. My next door neighbor has about an acre of endless lawn, and my neighbor on the other side has about half an acre of lawn. The neighbors across the street and nearby also have acres of manicured lawn also. I probably have almost half an acre of lawn myself also, which I am in the process of shrinking down to less than a quarter acre and hopefully further with a good food forest design for my front yard.

The Japanese beetles have swarmed my yard in years past, wreaking havoc on especially the grapes and cherries, rendering them almost leafless in a month or so, and then hitting some of my other plants. I had tried removing them by hand, but there were literally hundreds, and it never did anything, they just kept coming and coming, mocking me and breeding everywhere as they feasted on my plants.

Fast forward to this year. They came out in their usual numbers, putting a hurt on their favorite plants as usual. I'm sure that I drew in most of the neighborhood pests.. This was the first year that I let a good amount of the wild plants grow, so it took them a little while to grow up some. By mid summer once the wild plants started getting some good growth on them and the diversity of plants had increased, in maybe July or August, a drastic change occurred. Within a month's time, there went from being literally hundreds of beetles, to where most of the time I couldn't even find one after searching.

My cherries held most of their leaves all the way until winter, which was unheard of in years past, and the newer growth was also extremely green and healthy, and generally untouched by bugs or disease.

This is when I found the robber fly above with what may have been one of the last beetles nearby.

Mk Neal wrote:Cool!

Michael Fundaro, your fight against the beetles may be hindered by neighbors-- if you are surrounded by a lot of lawn grass, then the larvae are feasting on the grass roots before attacking your plants. There is a natural remedy called "milky spore," but unless neighbors treat also it may be futile.

My neighbor next door, and a neighbor diagonally across the street both have lawns, but no one else within a few streets have lawns.  I understand what you are suggesting but the Japanese Bark Beetle has been killing pine trees all across the mountain west for years and very few people have lawns at their mountain ranches and cabins.  I have been told, and learned by reading up, that the Japanese beetles fly around until they find a week, susceptible tree, then they attack the tree and give off a pheromone to attract more until they swarm the tree and attack until the tree can not fend off the beetle and dies due to the loss of moisture.  

I was hoping some sort of plant would kill or repel the beetle.  I don't have a lawn, and probably can't kill the neighbors lawns.

I think the Japanese bark beetles destroying trees are a different beetle than the one I am talking about that pupates in lawns and feed on garden foliage:

The tree pest is maybe this one: Japanese cedar longhorned beetle, Callidiellum rufipenne https://content.ces.ncsu.edu/japanese-cedar-longhorned-beetle

The lawn pest that people use milky spore against is: Japanese beetle Popillia japonica https://extension.umn.edu/yard-and-garden-insects/japanese-beetles
The adults feed on leaves and flowers, but not bark.

In my own yard, which is perhaps 1/3 barely maintained "lawn" surrounded by a mix of flowering and fruiting trees & shrubs and a mix ov vegetables and flowers, I see only occasional Japanese beetles, usually on the grapes or the roses; never enough of them to cause real damage. However, my mother's yard in Minnesota gets mobbed by them every year; especially on astilbe and roses.  She has a bit more turfgrass than me, but she likewise has a mature garden of shrubs, trees, and perennial flowers that supports a variety of insect life. I pretty much learned my gardening habits from her, so I do not think that I can attribute my avoidance of the beetle plague which she suffers to my gardening practices.

I have puzzled over this, wondering if maybe there is some critter here in my neighborhood which is either out-competing the beetle grubs so that we just don't get so many adult beetles, or maybe eating them before they emerge. We do have a lot more cicadas and lightening bugs, which also are grass-loving grubs, so maybe they (or some other less flashy bug I don't notice as much) crowd out the beetles?  

Bird predators and distraction plants for Japanese Beetles - my two discoveries from summer of 2020.

Hello everyone! I am new and here is my first contribution :-)

I have previously read that native birds were not interested in Japanese beetles, which was a disappointment. HOWEVER! This summer, to my big surprise, I personally witnessed a male Cardinal gobbling them up from a branch on a young tree in my backyard (an elm, I believe). I am not sure if that was an "opportunistic lunch", or if Cardinals actively seek them out, but who cares, at least there is a creature in the natural world that will eat them! I talked to my gardening neighbors and confirmed that they too saw Cardinals feeding on Japanese beetles. One of them said she kept a feeder in the middle of her rose shrubs stocked even in the summer, and once the birds were there, they took care of the bugs to her satisfaction. It should be noted that Cardinals are not very "acrobatic" as compared to, say, chickadees or nuthatches, so a feeder with a flat feeding surface is needed to make sure they are able to hang out at the feeder for some time. Has anyone seen any other birds feed on Japanese beetles?

In addition, last spring I happened to plant a few native flowers around my rose shrubs, and one of them seemed to act as a "sacrifice/distraction/trap" crop, in that if the year before all of the Japanese beetles were piled up in rose flowers, this year there were hardly any on the roses growing next to this flower. Instead, the beetles were mostly on this flower plant, which is a White Gaura (see photo). I am planning on planting more of all kinds of Gauras! It proved to be a very happy-go-lucky plant. The base crown forms a roundish ball of attractive blue/green foliage and stays evergreen in my Zone 7 climate (the bunnies did a number of it this winter though; but they did not bother it in the summer). It flowered profusely from early spring to mid/late summer, and was teaming with all kinds of small-ish bees and other insects feeding on nectar. The flowers are long stemmed, small, flat and white, so the beetles are very visible on them and it was very easy to grab a cup with some soapy water and shake the beetles off into it with precision difficult to achieve with rosebuds and flowers as beetles bury themselves in all those petals. With all these beetles hanging out on the Gaura, the plant itself did not seem to incur any damage or show any stress; it never slowed down flowering and there were no signs of chewing on stems or leaves..  

From what I could observe, another rose shrub within 10-15 feet of Gaura planting also benefited and was mostly beetle-free.  However, roses planted in the backyard (about 50+ feet away) lost the protection -  there were loads of beetles on them.

I'm delighted to see this topic come up because JBs are one of the most reliable pests around here. Due to their large travel area, it's virtually impossible to suppress the population with treatment on one's own land (especially here in the city). There's not a lot of good information available on natural controls, so by all means we should be comparing notes! Being invasive, JBs don't have natural predators in North America, but it stands to reason that some would be starting to figure it out, given how bountiful, dumb, and easy to catch the things are.

I'm going to look into what I can do to create habitat for robberflies now, and while we do have cardinals, maybe I'll work harder to specifically lure them to the garden.

Like Tanya, I've noticed JBs are attracted to gaura, in my case a Large-flowered Gaura (Gaura longiflora) growing in my native wildflowers. I've also noticed that while they love pole bean foliage in general, they go after some varieties much more vigorously than others. Last summer my "Fortex" were devoured while some "Blue Coco" growing right next to them were barely touched.

Here's my crazy idea that so far hasn't panned out but I would be delighted if someone else wanted to try out:

Supposedly certain geraniums have a stunning effect on JBs, which will be attracted to the flowers but then fall to the ground incapacitated for around 30 minutes. The source I read this from simply described the effective plants as "zonal geraniums", which is not a super precise classification. I acquired a couple zonal geraniums last year but only one flowered, and the JBs never showed interest in it. More experimentation is needed to see if certain varieties provide better results, and if I perhaps just needed more plants to get their attention in the first place. Anyhow, the plan is:

1. Plant a border with zonal geraniums with open ground beneath.
2. Attract birds to this area with bribes of seed or cool hangout spots.
3. JBs come for their flower fix, get knocked out, fall onto the open ground.
4. Birds discover the incapacitated JBs and eat them, because who doesn't like free lunch?
5. Birds acquire a taste for JBs, tell their friends, JB becomes trendy bird delicacy, JBs' reign of terror ends.

Ian Young wrote:
I'm going to look into what I can do to create habitat for robberflies now, and while we do have cardinals, maybe I'll work harder to specifically lure them to the garden.

Japanese beetles are only just arriving in Oklahoma and I have not seen any.  But I know a little bit about luring cardinals, and I highly recommend it!

They started showing up on my porch to clean up spilled dogfood (cheap big box store brand).  So we started feeding them something a little better for them (black oil sunflower seed and a cheap birdseed mix heavy on the millet) and put the feeder near my garden.  We get all kinds of birds but the cardinal flock exploded with regular feeding.  Instead of 3-4 birds we soon had half a dozen distinct family/flocks of them.  

I welcome them because they are among the bigger birds that regularly hang out in my garden now.  And the bugs that cause me the most pain are hornworms (big green buggers) and blister beetles (a pretty big bite for most small birds).  "Everybody" says birds won't eat either one for the most part; but my cardinals did not get the memo.  Last summer I only had one plant that got eaten by hornworms, but I saw evidence several times of plants that lost one branch before the hornworms mysteriously disappeared.  And blister beetles were routinely eating all the foliage off tomato plants pre-cardinals; now, I never see them.  I can't prove it but I think my cardinals eat pretty much anything that moves in my garden.  

So my joke is, if you want cardinals, feed them that cheap Walmart dogfood full of chemicals and food coloring; it makes them more colorful and very happy!  But in truth, just feed them.  ESPECIALLY during winter storms and when they are feeding babies.

To add to Dan's info regarding attracting Cardinals to your land, they are ground feeders and hang out and nest in dense shrubbery. I have a row of old and overgrown azalea bushes planted along the pine line, and I always see them in those azaleas. They love sunflower seeds. And they are VERY aware of your blueberry bushes :-) I have about 10 blueberry plants that are still in pots as I am yet to clear the patch where they will go. Last summer, to protect them from deer browse, I moved blueberry pots into the fenced veggie area, lining them up against the fence. They were within 10-15 fit of the tomato plants. At any given time, I had 4 to 6 Cardinals trying to get the berries. Cardinals and Robins seemed to spy blueberries VERY quickly, no matter where I moved them. The thing is, pretty much all birds are territorial, and any time you see more than one pair of the same species in close proximity, an "argument" ensues, and males start getting into each other's way and chasing one another rather than eating blueberries.. in the end, it's the Robin that got the berries lol. But both are larger birds able to handle larger insects. So if you want to attract birds to a specific area and not bother with having to maintain/stock a bird feeder, plant a couple of blueberries for them, one early season, one late.. I find that, if undisturbed, birds tend to hop around and investigate immediate surroundings...

And I second, I had no horn worm issue in this patch at all this summer (and horn worms are a big pest here too). For full disclosure, I did find two tomatoes that were pecked into, but it happened only once, so I will write it off as an accident :-)  One of the gardening books said that when birds peck into tomatoes they are seeking water/moisture, not the tomato itself. So having a source of water for them/birdbath should eliminate this problem. I wonder if this is also the case with other juicy edibles, such as peaches, for example.

Ian, I have not heard about the geraniums.. if you continue the experiment, let us know the results.

I have not seen robber flies around. It doesn't mean they are not around of course.. I will read up more about them. From initial research on wiki, it states that they prefer dry climates, which ours is not. But hey, if there is lots of food around, maybe I could coax them in!

I was surprised to see Okra work well as a trap crop here.  Japanese beetles would swarm it, eat the leaves, and it'd still throw off blooms and pods.  At 4-5+ feet tall it was easy enough to pluck beetles from the foliage in the mornings and drop them in a cup of water, then feed them to the chickens.  

Japanese Beetles attacked my raspberry bush last year. They were slow in motion in early morning so I was able to pick them off and tossed them in a water bucket. To my surprise, blue Jays found the bucket and ate all the drowning beetles. I believe birds are eating japanese beetles all the time.

JB's have recently started invading my garden, but as far as I can tell, they are only being a pest with my potatoes. They aren't 'bugging' anything else.The only obvious difference that I can see regarding the potato patch and the rest of the garden is that I had extensively planted marigolds and basil around my tomatoes, zucchini and squash.

Perhaps the scent of the goldies and basil are keeping them away?

Paul Sofranko wrote:JB's have recently started invading my garden, but as far as I can tell, they are only being a pest with my potatoes. They aren't 'bugging' anything else.The only obvious difference that I can see regarding the potato patch and the rest of the garden is that I had extensively planted marigolds and basil around my tomatoes, zucchini and squash.

Perhaps the scent of the goldies and basil are keeping them away?

JBs have strong preferences about which leaves they prefer to eat, so more likely than being deterred from the other plants, they just preferred your potato leaves to the other options. I've even had them strongly prefer one variety of pole beans to another, in plants growing side by side on the same trellis.

Ian Young wrote:
JBs have strong preferences about which leaves they prefer to eat, so more likely than being deterred from the other plants, they just preferred your potato leaves to the other options. I've even had them strongly prefer one variety of pole beans to another, in plants growing side by side on the same trellis.

Oh, well. A gardener can dream

My weird thought of the day for JBs is they are attracted to their own pheromones... Is there some kind of essential oil or something I can spray on the plants I want protected that would mess up the smell for them? I'm thinking I have rose geranium oil, might try it, mix it with water...

I'm happy to hear about cardinals are robins, got good crowds of both.

I have killed them before  by sneaking out pre-dawn, laying a tarp under the plants they are on, shake the plant well, and eliminate the JB's fast once I have them. They are sluggish and fall rather than fly on cool foggy mornings. Those days are beetle slaughter days here :)

:D

Pearl Sutton wrote:My weird thought of the day for JBs is they are attracted to their own pheromones... Is there some kind of essential oil or something I can spray on the plants I want protected that would mess up the smell for them? I'm thinking I have rose geranium oil, might try it, mix it with water...

I was just reading about using essential oils to confuse SWD finding fruit by smell: https://fruit.umn.edu/news/insect-repellents-berries. The verdict is: maybe! Probably worth a try with JBs too.

Pearl Sutton wrote:  They are sluggish and fall rather than fly on cool foggy mornings. Those days are beetle slaughter days here

It's interesting to read how different the JBs preferences are in different gardens. They're murder on my plum saplings struggling to get established, but they're most numerous on the asparagus ferns, where I can easily see them. I hold a small pail with soapy water under one (or often a mating pair) and knock it down. Mine tend to drop rather than fly at any time of day.

Michael Fundaro said, "I was hoping some sort of plant would kill or repel the beetle.

Michael, yes you can plant several different plants that will repel the Japanese Beetle.  Have you tried catnip, garlic, chives, or nasturtium?

Also, you can kill the Japanese beetle naturally with a soapy water or apple cider vinegar solution in a spray bottle.

We caught this beeline robber fly in our sunflowers the other day, and have also let a ton of  wild flowers and plants come up in our garden. Curious if anyone knows if they have favorite plants?

So amazing how they use camouflage of mimicry

Steve, How did your garden fare this year? Were you still infestation-free?

I looked up robber flies briefly. I Couldn't find any preferred plants but it does appear that their larvae hunt through decaying organic matter. Sounds like mulch to me. And it included rotten wood so hopefully my wood chip mulch works, too. Now I did discover that there are something like 1000 kinds of robber fly (also called assassin fly) in North America. So it could take a while to figure out which ones eat japanese beetles. But it sounded like they would eat most anything that flies. So that's promising.

Daniel

Hey Daniel,

I'm glad you posted to this thread, I had forgotten about it.

I don't think I even saw a Japanese beetle this year. There are also now many small trees in the area, which have seemed to attract lots of small insect eating birds. I was walking out there yesterday and in just 10 minutes saw probably 50 small birds in the small trees and plants busy patrolling.

Some of my apples produced for the first time this year and they were completely no spray. Here are a picture of two different varieties that I harvested last week. Even though we have extreme bug problems in my area, these apples were pretty much completely damage free.

Here's a picture of them after a little bit of polishing up with just a wet cloth. No one grows apples in my area, much less no spray apples, and I don't think it would have been possible without the small army of beneficial bugs and other animals doing their wonderful things.

Steve Thorn wrote:

Some of my apples produced for the first time this year and they were completely no spray. Here are a picture of two different varieties that I harvested last week. Even though we have extreme bug problems in my area, these apples were pretty much completely damage free.

Here's a picture of them after a little bit of polishing up with just a wet cloth. No one grows apples in my area, much less no spray apples, and I don't think it would have been possible without the small army of beneficial bugs and other animals doing their wonderful things.

I'm envious. This year JBs weren't the only thing afflicting my apples, but I have the bugs in great numbers. They chew a variety of plants here, including wild viburnum in the vicinity of the garden. Maybe the abrupt descent into winter last week will reduce their numbers. The Grub-B-Gone had no noticeable effect.

Hi Steve,
Good to hear that it wasn't just a one-off year with no JBs. Now to figure out how to replicate it in Colorado. I wonder if all robber flies would eat them or just one specie? Colorado doesn't have cardinals, so attracting them is out. But at least I do know that mulch is prime habitat for them.
Daniel

I'm from Denver CO and we had a sudden influx of JB's a few years back. It was blamed on a shipment of plants from back east that came to one of the country clubs near our home.  We milky spore'd, hand picked in the morning in to soapy water and thence to Compost heap, but resisted insecticides. They started out pretty picky. they LOVED our vine of Virginia Creeper and turned the leaves to lace pretty quickly. They destroyed our Grape Arbor. They loved to have orgies in the roses. They destroyed our red runner beans, which was a favorite of ours on a big trellis.

We mostly took out the Virginia Creeper (it's like MINT, you'll never totally get rid of it) and I leave it on the other side of our driveway as a "beetle trap." We took out the grape vine. We clip the roses after the beetles show up, seems like they love the flowers but that's it. My wife tears a bit when we have to trim off all the roses.

My daughter brought over their chickens a few years ago and it was like a scene from Jurassic Park. Feeding frenzy. Every time I see "vegetarian fed" on an egg container I just have to laugh. But my daughter's family moved away to Tennessee so no more chickens.

After we cleaned out their favorite food, they branched out and now get on marigolds, some random trees, the raspberries (which seem to be able to "outgrow" the beetles.) This past summer was the best we've had in a while, but it was also hot and dry and I had a lot of things to do other than care for garden.

May have to try the Guara and see if we can attract some robber flies and birds to the yard. Just learning about the permaculture technique, very intriguing.

I've been patrolling for Japanese Beetles, but I was happy to see this today!

Daniel Kaplan wrote:Good to hear that it wasn't just a one-off year with no JBs.
Daniel

I now suspect that there are factors in the abundance of JBs that we gardeners can't clearly determine. After having a real plague of the buggers for the last couple of years, I'm seeing only small numbers in the garden this year. I think they are in the Liberty apple tree, but it's too big for me to monitor. I've got wild birds and abundant wild plant growth near the garden, and they had no obvious impact on the JB population in buggy years, so I can't attribute this year's dearth to abundant wildlife. It's a mystery, but I'm glad for the reprieve this year.

FROM; https://www.planetnatural.com/pest-problem-solver/lawn-pests/japanese-beetle-control/
"How to Control
In the early morning or late evening, shake beetles from plants onto ground sheets and destroy.
Place pheromone traps around the perimeter of your property as adults emerge (May-July).
Floating row cover (Harvest-Guard®) can be used as a physical barrier to prevent adult beetles from damaging plants.
Spread beneficial nematodes on lawns or mulch around plants to kill immature stages.
These microscopic, worm-like parasites actively hunt, penetrate and destroy grubs in the soil.

Studies have shown that Lawn Aerator Sandals (a.k.a. Spikes of Death) are equal to or more effective than some insecticides for managing Japanese beetle grubs.
 Researchers reported killing 56% of the grubs by walking over infested plots of lawn 3-5 times.

Milky Spore (Bacillus popilliae) is a naturally occurring host specific bacterium that attacks the destructive white grubs in turf.
 Apply 10 oz per 2,500 sq ft anytime of year when the ground is NOT frozen.
Surround WP (kaolin clay) forms a protective barrier film, which acts as a broad spectrum crop protectant for preventing damage from a large number of insect pests.
AzaMax contains azadirachtin, the key insecticidal ingredient found in neem oil.
 This concentrated spray is approved for organic use and offers multiple modes of action, making it virtually impossible for insect resistance to develop.
 Best of all, it’s non-toxic to honey bees and many other beneficial insects.
Safer® Grub Killer is an organic ready-to-use spray that is very effective against the larval stages of this pest.
 Easy to use, just attach the bottle to your garden hose and treat problem areas.
 Covers approximately 2000-4000 square feet and continues working for up to 7 days.
As a last resort, spot treat adults with botanical pesticides.
 Apply to all leaf surfaces and deep into the plant canopy where insects hide.