Japanese Beetle Solutions

Japanese beetles on zinnia

Do you have Japanese beetles in your garden? I’ve had them for many years now, and I’ve tried several solutions for dealing with them. I'm happy to report that I’ve found a solution that helps. “Helps” is the key word. This method doesn’t eliminate them, but it definitely reduces the number.

leaf damage from Japanese beetles

Tell-tale leaf damage from Japanese beetles—they can quickly skeletonize foliage.

Before we discuss what's worked, what have you tried?

Methods I haven't tried:

  • I've never used beetle traps because most sources say they actually attract more beetles. Apparently, the traps (treated with flower scents and pheromones) and the dying beetles (also releasing pheromones) draw more beetles in.
  • I don’t use insecticides in my garden, so that option was off the table. Plus, they have to be regularly re-applied, and even the “organic” ones are harmful to other insects and pollinators. (With that said, I do use organic neem oil on indoor plants.)
  • Diatomaceous earth is another method—but it, too, can be harmful to monarch caterpillars and other garden critters. So, again, not an option I was willing to consider.
  • Applying nematodes is another method some gardeners recommend but one I haven’t tried. Several issues here: they have to be applied at certain times of day and certain times of year, they must be a specific species to be effective at eliminating Japanese beetles and the soil and soil moisture must be optimal for them to work.

 

Methods I have tried:

  • Soapy Water — With this method you can simply pick the beetles off the plants and drop them in the bath, or shake them off the plants into the water. Mix a couple tablespoons of dish soap with water in a small (approx. two cups) container. Empty beer or soda cans work well because the beetles have even less of a chance to escape. The soapy solution kills the beetles—they drop to the bottom and drown before they have a chance to release pheromones.
  • Soapy Spray — You can mix the same ratio of dish soap with water in a spray bottle, and spray it on your vulnerable plants. The problem with this method is that you’re likely killing and repelling beneficial insects at the same time. So, while I've tried it, I don’t feel good about it.
  • Japanese beetles on hibiscusStomping — If you only have a few Japanese beetles (other methods are working but the beetles aren’t eliminated), you can pick them off and quickly stomp them. This destroys them fast before they have a chance to release those pheromones.
  • Companion Planting — Some plants, like garlic, scallions, marigolds and catnip, tend to repel Japanese beetles. Try interplanting these repellents among other plants in your garden to help keep beetle numbers lower.
  • Milky Spore — This method works best for me. I’ve been using it for a few years now, and it seems to have significantly cut down on the number of Japanese beetles in my garden. The trick is that you need to place it in the garden in late summer or early fall (late August-September). The two main reasons? Ideal soil temperature for effectiveness is 60 to 70 degrees, and it only works on the grub stage of Japanese beetles, which are more active, close to the surface and prevalent late in the season.

Since milky spore is only effective against Japanese beetles, it won’t harm beneficial insects. It’s organic and extremely safe for use around children, pets and non-targeted species. It offers long-term, ongoing control, and only needs to be applied once per season. Follow the directions on the container for application, and then water the treated area to help the milky spore soak in and reach the grubs.

Don’t expect dramatic change after the first year of treatment; it can take up to three years to see a significant decline. I did notice a reduction after a couple of years, and even more each year since.

Here are two great sources for more information on eliminating Japanese beetles: HGTV and Growing a Greener World. Good luck!

 

Beth Stetenfeld is an organic gardener, native plant enthusiast and garden blogger and writer. She’s also a master naturalist volunteer and instructor.

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12 Comments

  1. Roberta Douglas Gale on August 6, 2022 at 6:06 pm

    Danger! When I first used a Japanese Beetle trap, after two days it was filled with BEES. I took it back to the store, and told them I thought they should not sell the product. So I pick the beetles and drop in soapy water.

    • MSHS on August 8, 2022 at 4:01 pm

      Oh no! That’s the tricky part with some of these control methods – other important species are inadvertently caught in the crosshairs, unfortunately. Thanks for making the effort to protect pollinators in your garden. The soapy water method can be time consuming but really does seem to help control beetle populations over time.

    • Gardengirl on August 9, 2022 at 10:15 pm

      Thank you gir protecting our bees. ❤

  2. Maggie merkow on August 6, 2022 at 10:35 pm

    Beetlejus works pretty well for me especially in big areas like trees and respberries

    • MSHS on August 8, 2022 at 4:07 pm

      Good to know – thanks for sharing, Maggie. Another reader just shared the same tip!

      • Gardengirl on August 9, 2022 at 10:02 pm

        My urban landscape 70 x 120 ft was stripped of all foliage due to Japanese beetles. No foliage on plum and apple trees, no foliage on roses, garden gone. I ripped out all of my Rose’s because they are reputed to attract the beetles. I picked beetles the first 2 hours on the am but i didnt make a dent in the problem, nor could I pick my trees (15 to 30 ft tall). Insecticides were not an option so I used Milky Spore BUT I did not apply as directed….droo a spot every (3 meters?). I had a major infestations and it was too hard for me to measure and apply so I poured it in a lawn spreader and away I sent over the lawn, through the garden, and under the trees. The next year i had NO beetles. Haven’t had beetles in 10 years but my immediate neighbors do and whine continually. I just smile because 10 years ago I suggested using Milky Spore and they ignored me. Now I ignore them, . I have since learned that linden trees attract beetles and our street is lined with lindens so if possible, remove the main draws.

  3. Jay H Steele on August 7, 2022 at 12:45 am

    Japanese beetles have taken some of the joy out of gardening for us in Burnsville. We once had more than 50 roses, shrub and tea. For several years we just trimmed them all back for several weeks until the beetles declined in early August. But what’s the fun of having roses if you can’t have flowers. We also removed a large Linden tree in our front yard that would be be full of beetles and defoliated by summers end.

    We have controlled by knocking them into soapy water, hundreds a day sometimes.

    However, over the last couple years we have seen more and more beetles with the tell-tale white dots on their heads of eggs of the winsome fly. This year we are seeing significant numbers of these beetles with white specs on their heads.

    This summer we have noticeably fewer beetles. Still too many. Cold winter? Parasites? Or just luck? I don’t know but I am hopeful we might be reaching a nuisance rather than pestilence phase.

    • MSHS on August 8, 2022 at 3:57 pm

      Sure hope you’re right about a nuisance rather than a pest phase, Jay. They just decimate those roses, don’t they? So frustrating. We’re rooting for those winsome flies! Great news that they’re taking hold and hopefully having some effect on the beetles in your yard. Keep us posted.

    • Gardengirl on August 9, 2022 at 10:12 pm

      Not a coincidence. Theyvhavr found that fly will kill the beetles and are now using it for beetle control. UW Minnesota just released info and you might want to look at it.
      Sounds very promising.

      Removing the Linden probably made a HUGE difference as that is one of the primary draws for JB. My street was lined with lindens and I am convinced that was the reason we were decimated in my neighborhood. Two of the lindens on the terrace I had removed due to disease and I had fewer beetles. 10 years ago I gave up on my rides, ripped them all out when I learned that like the lindens they were a JB favorite.

      Theres hope! After being jp free, I’m planting Rose’s again.

      Good luck!

  4. Susan Kirchner on August 7, 2022 at 11:38 am

    I pick beetles and drop them into soapy water as my main method of control. I have utilized the BTg product called BeetleJus from Gardens Alive on my raspberries when the infestation is very heavy. I also use drip irrigation in my raspberries so it minimizes the area of soft soil in which the beetle can lay eggs.

    • MSHS on August 8, 2022 at 4:06 pm

      Good tips – thanks, Susan.

  5. Grace Leung on August 10, 2022 at 12:23 pm

    I catch them one by one. First year I got 500 and drown them in soapy water. Next year I have 380-ish…this year because of dry season (?), I caught only 10.

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