Tuesday

What You Need to Know About Getting Rid of Japanese Beetles


It's June, and my email account is overflowing with pleas from desperate gardeners. What's the big disaster? Japanese Beetles. From a purely visual point of view, the iridescent green carapaces of these insects are lovely -- but the little beetles themselves are evil, evil, evil. They can devastate your beautiful raspberries and lay waste to your rose bushes in less time than it takes to assemble that new patio furniture you're so proud of. If your landscape is experiencing a Japanese beetle infestation, you probably don't need any more descriptions of the damage they're capable of.

There is a lot of confusion about getting rid of Japanese Beetles. I'm a San Francisco Bay Area resident transplanted to the Midwest, so this particular garden pest wasn't on my radar a decade ago. When I saw my first Japanese beetle, I thought it was cute. Imagine. Here are a few hard won JB facts I've learned that you should know about:

Stopping a New Japanese Beetle Infestation Cold (Homemade Repellant)

Japanese Beetles overwinter in the soil. If your property has been spared in the past and this year you decided to plant, say, rose bushes, you are making your landscape more attractive to Japanese beetles and should be prepared to deal with them when they emerge in late spring. Here's the part that can be difficult to get a handle on:

If you haven't had beetle problems before, here's how it works: Scouts will follow the scent of new, tasty plantings to your property. Once they realize that you have good greens on offer, they'll invite their friends to come along for a free meal. Natural Japanese beetle control works great in this situation because you probably don't have beetle grubs emerging from your soil (more on that in a second). Here's how natural control works:

Snag JB scouts in June when they start to emerge from the ground and toss them in a bucket of soapy water. They're big enough that you can just grab them with your garden gloved hands. If you're squeamish about this method, you can knock them into the bucket by holding it next to the plant and shaking the branch. Plop, the beetle lands in the water and dies soon thereafter. Now, leave the bucket with the dead beetles inside near the plants that seem to be attracting the bugs. (By all means, keep adding to the carnage in the bucket as you discover new beetles.) Arriving beetles will get the scent of dead beetles and steer clear.

When Nabbing Japanese Beetle Scouts Won't Work As Well

This will not work nearly as well if you had a beetle infestation last year. Instead of the emerging beetles from down the block flying to a new location (your property), the grubs are probably already in your soil. When they emerge, lunch (your roses and other lovely plants) are waiting for them like an all-you-can-eat buffet. They just hop onboard and start chewing. Think of them as pesky residents. Your shrubs and plants are the first stop on their to-do list.

Other Ways of Discouraging Japanese Beetles

If you've had problems with beetles in past seasons and think they may be in your soil, there are a number of methods you can use to get rid of them:

Herbal and Organic Sprays - There are lots of natural methods for killing an established beetle infestation. You will probably have spotty luck, though. There are millions of beetles out there, and for every one you evict, another will be along in a few minutes.

It may not be quite that discouraging, but when you see your flowers so completely covered with voracious beetles that their stems are actually bending under the weight -- well, that's a sad day. Natural insecticidal soaps kill beetles that come into physical contact with the wet spray, but spraying the plant won't kill beetles that ingest the soap. Neem extracts are another natural option.

Insecticides -Multiple and diligent applications of insecticide over the course of the summer months can control Japanese Beetles, but it won't eliminate them. This may seem like the most efficient choice, but it probably won't be as effective as you expect -- and you'll have to keep reapplying the insecticide regularly. Insecticides aren't selective, either. They kill the beetles, but they also kill beneficial insects like honey bees and lady bugs. The following insecticides kill Japanese beetles, but they aren't the only varieties that will do so.

For adults, you may have success with Malathion.To control grubs, some gardeners prefer Diazinon.

Check the labels at your garden center for options like: Sevin, Malathion, Rotenone, Diazinon, Ortho Bug-B-Gon and Spectracide.

Traps - Traps attract beetles and kill them. This sounds like a great idea, but because there are so many beetles in some areas of the country, attractants are like ringing the dinner bell. The traps don't catch all the beetles (the USDA suspects they capture about 75 percent of beetles that approach), and the survivors eat well and attract more beetles -- and more -- and more.

Nematodes - Nematodes are microscopic worms. You introduce them to your soil in spring or fall and they kill Japanese beetle grubs before they have a chance to emerge. There are lots of nematode varieties; some are beneficial in the garden and some are not. Using nematodes to control beetles can be a twofer: Nematodes that kill Japanese beetle grubs also kill other pests like flea beetles and bagworms. This is an all-natural option and nature's way of handling the problem, too. One nematode variety that kills Japanese beetles is the Heterorhabditis bacteriophora, but there are probably others, too. Ask your local garden shop for suggestions. Once you eliminate the next generation of beetles on your property, you can use another method, like an organic spray, to get rid of any wayward newcomers.

Milky Spore - This is another organic choice, a bacteria (Bacillus popillae-Dutky) that kills the grub stage of the beetle while it's in the soil (like nematodes) and isn't destructive to plants or beneficial garden insects. Milky spore reproduces in the dying grubs and creates a generation of millions of microscopic warriors blanketing your soil with organic Japanese beetle protection.

As with nematodes, this option won't help get Japanese beetles out of your backyard this season - it will help you control the pests next season and beyond, though. Milky spore comes in granule form. You can apply it to your lawn the way you would fertilizer.



Best Practices

You can see that the best way to control Japanese beetles is to tackle the problem before they become active on your property. After they're present in big numbers, your best option is:
  1. Deal with the infestation as best you can this season using herbal methods or insecticides.
  2. Apply nematodes or milky spore soil treatments to kill the immature stages of the pest before they emerge next year.
  3. Start watching for Japanese beetle scouts next year around the time they're scheduled to emerge and use the soapy water/bucket method to kill them and keep them from spreading the word to other beetles. You can contact your local Cooperative Extension Office to get a better idea of the date Japanese beetles are likely to emerge in your area. They're pretty reliable, and the experts can narrow it down to a two week period or so.
Plants that Attract Japanese Beetles

The easiest way to avoid problems with Japanese beetles is to steer clear of landscape plants and trees that attract them -- if you can bear to forgo some of these garden favorites. If you were a Japanese beetle, these plants and trees would be on your birthday wish list of tasty things to eat:

  • Althaea (Althaea spp.)
  • American mountain-ash (Sorbus americana)
  • Apple, crabapple (Malus spp.)
  • Apricot
  • Asparagus (Asparagus officinalis)
  • Beech (Fagus grandifolia)
  • Birch (Betula spp.)
  • Black walnut (Juglans nigra)
  • Cardinal flower (Labelia cardinalis)
  • Cherry
  • Clematis (Clematis spp.)
  • Common mallow (Malva rotundifl ora)
  • Crape-myrtle (Lagerstroemia indica)
  • Dahlia (Dahlia spp.)
  • Evening-primrose (Oenothera biennis)
  • Gladiolus (Gladiolus spp.)
  • Grape (Vitis spp.)
  • Hawthorn (Crataegus spp.)
  • Hibiscus (Hibiscus moscheutos)
  • Hollyhock (Alcea rosea)
  • Horse-chestnut (Aesculus hippocastanum)
  • Japanese maple (Acer palmatum)
  • Larch (Larix laricina)
  • Linden, American, European (Tilia spp.)
  • Lombardy poplar  (Populus nigra var.)
  • Morning-glory (Ipomoea purpurea)
  • Norway maple (Acer platanoides)
  • Peach
  • Pennsylvania smartweed (Polygonum pensylvanicum)
  • Peony (Paeonia spp.)
  • Pin oak (Quercus palustris)
  • Plum
  • Red raspberry (Rubus idaeus)
  • Rhubarb (Rheum rhabarbum)
  • Rose (Rosa spp.)
  • Sassafras (Sassafras albidum)
  • Soybean (Glycine max)
  • Summer-sweet (Clethra spp.)
  • Sunflower (Helianthus annuus)
  • Sweet corn (Zea mays)
  • Virginia creeper (Parthenocissus quinquefolia)
  • Willow (Salix spp.)
  • Zinnia (Zinnia spp.)

[source: USDA]

Good luck and happy gardening.


References:


Blue Horizon Farm. "How to Control Japanese Beetles In Your Organic Vegetable Garden."
http://www.bluehorizonfarm.com/organic-gardening/japanese-beetles.html

Featured Creatures. "Japanese Beetle"
http://entomology.ifas.ufl.edu/creatures/orn/beetles/japanese_beetle.htm

U.S. Department of Agriculture. "Managing the Japanese Beetle: A Homeowner's Handbook." (This is a free PDF download.)

University of Kentucky. "Japanese Beetles in the Urban Landscape." 2010.
http://www.ca.uky.edu/entomology/entfacts/ef451.asp

Photos:

Image 1 - JapaneseBeetlesWiki.jpg By D. Gordon E. Robertson (Own work) [CC-BY-SA-3.0 (www.creativecommons.org/licenses/by-sa/3.0) or GFDL (www.gnu.org/copyleft/fdl.html)], via Wikimedia Commons

Image 2 - JapaneseBeetlesWiki2.jpg By Lamba at the Italian language Wikipedia [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/)], from Wikimedia Commons

10 comments:

  1. Great article. We moved to zone 7 OK from northern CA and have been appalled at how challenging it is to grow stuff here.

    Keep giving us good tips.

    ReplyDelete
  2. Thanks for the info. The JBs are all over our grape vine now (early July), and I have been knocking dozens and dozens of them into a bucket of soapy water, but then I dumped it way away from our yard, because I thought I had read that even the scent of dead beetles attracted more. Sounds like I am mistaken?

    Anyway, I think the vine is lost to the beetles now, and we will have to try nematodes or something to help battle next year's hordes.

    ReplyDelete
    Replies
    1. Hi Nicole,

      As I understand it, Japanese beetles aren't attracted to the smell of dead beetles. They're attracted to the sex pheromones and a floral lures added to Japanese beetle traps.

      Delete
    2. I agree -- the floral lure is what attracts the beetles. Unfortunately I bought a JP trap our first summer in our new home...soon, every beetle in South-Central PA was in my yard buzzing around the trap. Yes, I caught hundreds, but honestly I think the lure attracted more to my garden than dissuaded them. :(

      The following year I kept a jar filled with soapy water on my back porch step -- picked 'em off and drowned 'em as I saw 'em. I was surprised at the decline in beetles. I would agree the smell of the dead beetles keeps other beetles away!! :)

      Delete
  3. I had never seen a Japanese Beetle in Texas until last week. Now they are everywhere. Flying through the air, and flying right into me. I know my brother had trouble in Indiana with these creatures and I want to get rid of them NOw!!!!!I am going to the store to get everything that was mentioned. I could never live with theses bugs. They wreck the daytime hours. Then you have to deal with Mesquitoes and June bugs at night.

    ReplyDelete
  4. Oh My Gosh!!! I was looking down at what was eating the leaves of my beautiful flowers, when I happened to see something fly by, making me glance upwards. To my horror, there were tens of thousands of Japanese beetles making my wisteria tree their lunch! It was like a bad movie! I couldn't waste time making anything organic - I ran to the basement and grabbed my Ortho insect killer and started spraying like a mad-woman! They were flying around me everywhere and making these evil noises! I will most certainly be having nightmares tonight. UUGGHHHHH!!!!

    ReplyDelete
  5. You've listed a list of plants that attract JBs. Are there ANY plants that they shy away from? And catching them with a gloved hand is not as easy as it sounds - they can be very quick. I usually try and nab them when they are mating on the plants. Most plants that they eat may look terrible, but usually make a comeback and survive.

    ReplyDelete
  6. Does milky spore or nematodes harm earthworms? Cuz i actually raise earthworms to release and help my garden. thx !

    ReplyDelete
    Replies
    1. Both parasitize destructive earth dwelling grubs and insects but leave earthworms alone.

      Delete
  7. I cut mint sprigs & played them in the branches of my infested giant hibiscus. The number of Japanese Beetles declined immediately. Then the ones remaining I drowned in my soapy bucket. They were also munching on Crepe Myrtle.. The ssooo much ..

    ReplyDelete

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