ways to combat Japanese Beetles

hubcap93(5a)February 17, 2014

Am looking for ways to combat Japanese Beetles, they have decimated my roses where they get so week from the onslaught that they can't survive the winters here. when spring pruning the dead on the canes is so bad and so far down that they aren't salvageable, nothing left of the bush. another problem is that I'm gone during the week so am not able to continue to watch them basically Mon. thru Friday, any suggestions would be greatly appreciated.

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dublinbay z6 (KS)

My understanding is that there is just about nothing anyone can do--short of moving to the North Pole.

I remember a couple posters saying that when the JB appear, they go out and pick every decent bloom in the garden and make all sorts of indoor bouquets. They figure they might as well enjoy the blooms as let the JB enjoy them.

I think the idea is that the JB don't settle in --at least not in significant numbers--when there are no blooms to guzzle. And by the time the rose bushes get around to putting out a new cycle of blooms (maybe a month or 6 weeks later), most of the JB have left anyway.

I don't have any real JB problems here--an occasional one or two or maybe a half-dozen show up, but that is it--so I can't really say what to do, but I always thought that the above methods were at least practical, even if they aren't a real "solution" to the problem.

Something to think about, anyway. Good luck.


    Bookmark   February 17, 2014 at 8:05PM
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Picking blooms off doesn't always work. I have several OGR's that don't repeat bloom so they are done blooming before the JB's show up but the JB's will eat the leaves of these roses as well as the leaves of some of my repeat blooming roses. If you are willing to use insecticides there is one available that finally has some residual kill & repel effects. Below is a link to a rose blog that has info on it. It is not a perfect control answer but I've found it to be about the best thing out there.

Here is a link that might be useful: rose blog

    Bookmark   February 17, 2014 at 8:24PM
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AnneCecilia z5 MI

I read that rose blog on the chemical Demand CS, Wirosarian, and also read the label information that the blogger posted. That's some scary stuff - certainly no more environmentally friendly or safer for the user than Merit (Imidacloprid),. Do you really want to put something into your garden that recommends contacting a physician if you get it on your skin, is quite toxic to fish - and to pets? And what about the poor bees? (I don't believe for a minute what the blogger writes about not noticing any effect on beneficial insects. I never noticed any dead bees either back in the days when I used Merit, but I now know research has proved it to be very harmful.)
From the Demand CS label:
"This product is highly toxic to bees exposed to direct treatment or residues on blooming crops or weeds. Do not apply this product or allow it to drift to blooming crops or weeds if bees are visiting the treatment area."

Is it really worth it? Believe me, I've waged the war with both rose chafers and now Japanese beetles, too. I know the frustration...but in the end, after researching the chemical weapons I just can't justify their use. Just asking you to think and read up on them before you grab for a spray bottle.

    Bookmark   February 18, 2014 at 6:31AM
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I'm experimenting with some natural deterrents, though I don't expect it to get rid of all (if any). I read that rue will repel them so I've planted it around a few of my roses. Plants aren't full sized yet, but thought I'd compare to other beds where it isn't planted. I'm also going to try annual geraniums. Supposedly if JBs eat the geraniums it will paralyze them making them easy snacks for birds.

Mostly JBs hit us after the first flush and are gone before the rebloomers kick up again.

Hoping this freezing winter is good for something and our JB batch is lighter this summer because of it.

    Bookmark   February 18, 2014 at 8:54AM
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anntn6b(z6b TN)

By far the lowest impact is to use Japanese Beetle traps.

We have used up to twelve on our property, putting them up at first appearance. We did this for five years. We also modified the traps to be able to 'empty' the bags, so that we really got almost all of the beetles.

Then we dropped back to five bags and were able to see a major difference.

Then we had two years of severe drought. That drought made the clay that I grow roses in almost useless as a place for egg laying (I remember watching a June Bug try and the poor girl got nowhere for seven minutes and then I squished her.).

Drought when the grubs are emerging also helps as does drought in fall when they are feeding on roots.

The one thing that you should not, in my opinion, do is nothing. "Nothing" leads to their wanton reproduction. Each female can lay 20 eggs a year.

Do the math for five years of doing nothing.

Traps have two attractansts: JB pheromones and rose scent. Both of which are going to attract beetles to your garden even if you don't buy beetle traps. Traps will, at the very least, knock the dickens out of JB populations.

    Bookmark   February 18, 2014 at 10:48AM
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AquaEyes 7a New Jersey

Maybe you need some chickens...see videos below. While this isn't a feasible option for everyone, it is rather entertaining to watch.



Part 1

Part 2

    Bookmark   February 18, 2014 at 1:42PM
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seil zone 6b MI

I've always heard that if you want to use traps, put them in your neighbors yard! Supposedly they only attract more of them.

I do use a Grub-X type product to kill them while they're in the soil. It has reduced the numbers I get considerably. You put it down on your lawn in the early spring before the grubs turn into beetles. It lasts for several years before it needs to be repeated.

This month's American Rose magazine has an article about someone who uses a small battery operated computer keyboard vacuum to suck them up! He says it works like a charm and does little to no damage to the roses. I'm tempted to give it a try.

    Bookmark   February 18, 2014 at 3:12PM
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Milky Spore Disease works here but takes a few years for full effectiveness. The advantage is that it is the gift that keeps on giving, that is, it will continue to spread and increase in effectiveness over time. I spread it over the treated area at about 50% recommended dosage to save money and because Milky Spore spreads, this system works. It can die out in a drought year but I have only had to apply it twice in about 20+ years. The birds also help a lot so bird baths and other bird accommodations may help.

    Bookmark   February 18, 2014 at 4:04PM
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AnneCecilia z5 MI

I like that little keyboard vacuum idea, Seil - I always seem to manage to knock a few beetles to the ground instead of into my bucket of soapy water and the little creeps burrow into the mulch and disappear in a blink. I'm tempted to see how much one of those vacuums would cost - and I wonder how many beetles will fit in the collection chamber?
Birds do indeed help a bit. I've witnessed Eastern Kingbirds and Bluebirds hard at work collecting beetles in my garden. A fountain with shallow bowls can be a terrific bird attractant as the moving water brings the birds in and they hang around to bathe in the water, then perch nearby to preen and dry...and perhaps spy a beetle or two! Plus IME there are always a few beetles that drown themselves in a fountain which makes for a little bonus.
Traps may *seem* to bring more in, but I suspect that is an illusion. At least those that enter don't get a chance to lay their eggs and increase the population.

    Bookmark   February 18, 2014 at 7:34PM
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catsrose(VA 6)

I also use Milky Spore and since my grass connects to my neighbors, they get it too as it spreads. It's expensive and I have an acre and a half, so I buy a canister every year and just keep expanding my coverage. The birds help and I put up bluebird boxes. When I was turning over one of my first new beds here, I hit a huge patch of the grubs. I just tossed them onto the drive way, intending to stomp on them when I got up. But a pair of bluebirds saw them and braved my presence to swoop down and munch them. I still get a few JBs but nothing like the first two years I was here. Oh, and they will eat leaves as well as blossoms. I've seen them devour a weeping cherry in a matter of days.

    Bookmark   February 18, 2014 at 8:14PM
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nikthegreek(9b/10a E of Athens)

Lambda-cyhalothrin (the active ingredient in Demand CS) is a pyrethroid, similar but not exactly equivalent to deltamethrin, permethrin etc etc. It is widely used for mosquito control. Pyrethroids are non-systemic insecticides and thus by definition have less of a residual effect than neonicotinoids (imidacloprid, thiamethoxam) thus making them somewhat 'safer' to beneficial insects. However they are broad spectrum insecticides too so most insects will be affected by them. The CS after the brand name signifies the pesticide formulation as 'Capsule Suspension' a way of delivery utilising 'microcapsules' that will reportedly increase residual activity. Sustained use of pyrethroids can have adverse effects on beneficials, may cause resistance to target insect populations and may cause mass infestations by non-target pests (e.g spider mites). Sustained use should be avoided IMO. If you choose to spray, try to spray during times of beneficial insect inactivity.

This post was edited by nikthegreek on Fri, Feb 21, 14 at 0:15

    Bookmark   February 19, 2014 at 8:10AM
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Milky Spore is not cheap, but as others have said, it is effective. What it does is significantly reduce but not eliminate the population of Japanese beetles. You do have to renew it from time to time.

Nothing that wipes them out will altogether offer any lasting protection. If you were somehow able to kill every last one of them, a new wave of the beetles will move in, leaving you as badly off as you were beforehand.

    Bookmark   February 19, 2014 at 7:27PM
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Susanne27(5a Ontario Canada)

I have sandy soil, which they love. I have been dealing with rose chafers (not japanese beetles) since I planted my first rose. They stay for about 3 to 4 weeks starting in mid june and going into early july. My strategy so far is this: I plant repeat flowering roses so I will get to enjoy blossoms after the bugs are gone. I pick off the bugs several times a day and drop them into a soapy container. I know this isn't practical for many people with a lot of roses but I like the fact that the ones I kill aren't going to be mating. I have some 'trap' plants eg. fragrant old fashioned rose bushs that they prefer. These bushs don't ever amount to much in my garden anyway because of the chafers, so I keep them away from my rose garden and they attract the most bugs for me to pick off and kill. I bring blossoms into the house to enjoy if the chafers are going to get them anyway. The milky spore sounds like a good plan and I will look into that too. I personally don't notice too much damage to the leaves but rose blossoms are destroyed within minutes. The chafers love drought and are much worse on my sandy soil during a dry season or two. Keep up the good fight everybody and don't give up on roses.

    Bookmark   February 20, 2014 at 9:16AM
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nikthegreek(9b/10a E of Athens)

What exactly is Milky Spore? Some biological control agent, such as a bacillus, targeting beatles or their larvae? Will it target other kinds of chafers? Btw, resistance can develop to most such biological control agents.

This post was edited by nikthegreek on Thu, Feb 20, 14 at 10:07

    Bookmark   February 20, 2014 at 10:03AM
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Milky spore is a disease caused by Bacillus popilliae, a bacillus that attacks Japanese beetles. It is what keeps their numbers under control (at least in part) in their native Japan.

I would imagine that they do indeed develop resistance, just as we humans have developed resistance to diseases such as measles, once upon a time a widely fatal disease, though still so occasionally and still with the potential for serious side effects. This might explain why people report inconsistent results. My father had excellent results in his two-acre garden in rural western Pennsylvania, so I tend to consider it highly effective. Others are less convinced by their experiences.

There are other biological controls, both nematodes and parasites. I've listed a link to a University of Tennessee report that goes over this in detail, including the most effective chemical insecticides. I myself hesitate to use such insecticides because of their bad side effects, including harm to our honeybees, already at risk.


Here is a link that might be useful: U of Tennessee report on controlling Japanese beetles

    Bookmark   February 20, 2014 at 12:23PM
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Timing is important in Milky Spore application. It needs to be applied when the grubs are active near the soil surface. Here it is around June, shortly after mating season.


    Bookmark   February 21, 2014 at 3:41AM
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nikthegreek(9b/10a E of Athens)

Hi Cath,

My interest is purely out of curiosity since we don't have these pests over here. We do have other kinds of chafers that feed on roses though. We also have the horrible melolontha whose grubs can cause large scale damage. Regarding effectiveness and resistance take a look at the link below.

Here is a link that might be useful: Paenibacillus popilliae

    Bookmark   February 21, 2014 at 4:06AM
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thanks for all the response, really appreciated. I put grub-ex down every year and it works somewhat but living out in the country and with fields across the road and behind the house plus the fact that neither of my neighbors on each side of the house does anything to try and control it on their property makes me wonder if I'm just throwing my money away. we've used the traps and they definitely took out a lot of beetles, but i couldn't tell if it was just bringing more in or was it actually helping out. I've used soapy water spray and organic sprays and they help but in the end I still have them eating my roses. also the Japanese Beetles hang here generally from mid June through mid August so there here during the 2nd flush of my rose bushes which they just destroy which leaves me with the first bloom and the last bloom in September. again thanks for all of your responses i'm not abandoning the ship, and will continue to fight these invaders to the bitter end

    Bookmark   February 23, 2014 at 10:24PM
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Again - get a half dozen chickens and let them free range. The first year after I did this, I had SIX - yes, 6 - JB's.
I believe they grab the beetles as they emerge from the sod. Anyway, the year I didn't let them out much, due to new plantings that i wanted to protect from their dust baths, I had more beetles.

    Bookmark   February 26, 2014 at 8:59PM
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