Beating the Beetles

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Posted by @LarryR on
Beetlemania reigns at Cottage-in-the-Meadow Gardens this month. The full force of the Japanese Beetle onslaught has hit our flower beds. Come on in, check out the damage, and see how I'm dealing with the invasion.

Many of my gardening friends here in Iowa have complained for several years about the damage their gardens sustained from an invasion of Japanese beetles. I considered myself fortunate because my only encounter had been the odd beetle here or there on a rose blossom.

Not this year. The scourge has descended upon us with a vengeance. Check out the damage below and follow me as I attempt to deal with it.

Plants in Our Gardens Favored by Japanese Beetles

 2012-07-05/LarryR/a9d118  2012-07-05/LarryR/a00520
Scents play an important role in a Japanese beetle's life.  Here the scent of one beetle has attracted a whole cluster. This Buck rose ('Carefree Beauty') was in full bloom when the beetles struck.  It has been completely stripped of blooms.
 2012-07-05/LarryR/ae37b5  2012-07-05/LarryR/891089
Beetles beginning a feast on Rugosa rose 'Charles Albanel' Once the beetle assault became really serious, rose buds were popular targets as well.
 2012-07-05/LarryR/4a93cf  2012-07-05/LarryR/2e6f5b
Other flowers were also victims.  Here is a double oriental lily under attack. Canna blossoms were favorites.
2012-07-05/LarryR/2821a3 2012-07-05/LarryR/9b9b35
A calla flower sculpted by a beetle with an artistic bent Sweet peas proved to be a sweet treat.
 2012-07-05/LarryR/b46870  2012-07-05/LarryR/c79543
Not only the blossoms but the leaves of cannas turned out to be beetle magnets.  Here is Canna musifolia.  Interestingly, the beetles much preferred plain green canna leaves as opposed dark or striped ones. Variegated Fallopia japonica leaves were popular, too.
 2012-07-05/LarryR/4e765b  2012-07-05/LarryR/99d2ee
Food-producing plants were not immune.  Here beetles munch on grape leaves. Even asparagus foliage proved popular.  Aside from that, our vegetable garden was spared.


I took a fairly aggressive approach to the invasion.  The first two days were spent spraying with Pyola (see photo below), an organic mixture of pyrethrin (a chrysanthemum extract) and canola oil.  I sprayed three times a day, usually during peak activity, which was generally from ten o'clock in the morning to four in the afternoon.  The spray was quite effective, incapacitating most beetles on contact. 

Pyola is an organic mix of pyrethrin and canola oil

  Commercial insecticidal soap
You can make your own by dissolving 4 teaspoons Murphy’s Oil Soap and 4 tablespoons vegetable oil in one gallon of water.


Two-gallon sprayer

I also bought a spray bottle of insecticidal soap (see photo below left).  It turned out to be just as effective as the Pyola.  I carried it around with me as I made my garden rounds and zapped beetles that were at arms length wherever I encountered them.  I found that that strategy was better than firing up the sprayer every time I wanted to spray, and the spray bottle is decidedly more portable.  One advantage of the sprayer, though, is that I can reach fairly high up into the foliage, given the three feet of hose and nozzle on the sprayer plus the five feet that the spray travels when I pump the pressure up fairly high.

On day three, despite my success with the two organic sprays, a new wave of beetles descended on our three-quarter-acre gardens and overwhelmed them.  Encouraged by a friend's success with traps, I bought three (see photo at right below), though with some hesitation, as I had read that traps weren't effective because they lured beetles from neighboring areas to your garden.  I decided I didn't really care about that, since the more beetles I killed. the fewer eggs they would lay in our gardens and throughout the neighborhood.

Bring 'em on!

I got quite a surprise after I had assembled the first trap and was carrying it to its appointed location.  Beetles from everywhere made a beeline right for that pheromone-containing capsule on the trap.  I literally had beetles swarming around me, so many that they kept bumping into my body, including my face and head.  That made a believer out of me on the spot.  By the end of the day, my three traps were all at least two-thirds full of dead and dying beetles (see photo at right below).

The traps provided another advantage.  Beetles swarming around them made an easy target for my sprayers.  One or two squirts brought down a dozen or more beetles at a time.

I was in for another surprise--actually two surprises--when I emptied a trap of captured beetles for the first time.  The stench of decaying beetles is overwhelming.  Nauseating, even.  They smell like rotting flesh.  A scene from "Silence of the Lambs," where the characters put a dab of Vicks Vaporub under their noses to avoid the stench of decaying bodies, flashed through my mind.  Then I made the mistake of dumping the dead beetles upwind from our gardens.  Having to resmell those beetles several times as I worked in our garden beds was almost worse than dealing with the current heat wave that has engulfed the Midwest and much of the rest of the country.

           First day's catch
Each of the three traps were at least two-thirds full of beetles
This two-gallon bucket is half full of soapy water.  The pile of dead beetles from just one trap extends from the surface all the way down to the bottom of the bucket.
Capsule and vanes at top of trap

The second surprise was seeing some of the trapped beetles seemingly springing back to life and flying away as I emptied the trap into a bucket.  (I'll explain the reason for this below.)  To avoid that from happening with the other traps, I filled a two-gallon bucket (at right below), recycled from a remodeling project, with soapy water and sought the help of my wife, Wilma.  One of us held the bucket under the trap while the other dumped the bugs into it.  A quick stir with a stick assured that all the beetles were covered with water before any could fly away.

How the traps work

The Japanese beetle traps that I bought use no pesticide.  The active attractants are a floral scent and beetle pheromones.  The capsule containing these ingredients is positioned at the top of the trap (see arrow in photo at right below).  The four plastic vanes (same photo) around the capsule provide a very slick surface to which beetles cannot cling.  As they seek to land on the vertical surface, they fall helplessly into the clear plastic bag below, which is also very slick.  There is no escape, and the beetles eventually die from lack of food or from suffocation.

When emptying the trap, it's important to remember that the most recent victims will be on top of the pile and not yet dead.  That fact necessitates the use of the bucket of soapy water mentioned above.  The traps empty easily via a zip lock at the bottom of the bag.


After installing the traps on day three, the beetle count decreased noticeably on day four. As I write this, I'm on the sixth day of my beetle eradication regimen.  Each day has seen a decrease in the beetle count--and in plant damage--from the prior day. I expect our gardens to be relatively beetle free in the next day or so, barring another significant hatch of beetles in the area.


Two-gallon sprayer  $21.50
2 16 oz. bottles Pyola @ $16.99    33.98
2 bottles Insecticidal soap @ $14.99    29.98
3 Beetle traps @ $6.97      20.91
Total $106.37

You can help

Have you had experience with Japanese beetles in your garden?  Let us know how you fared and what measures, if any, you took.  Together we can learn more about what it takes to control an infestation.  I'll update my progress in the forum at the end of this article.


Comments and discussion:
Thread Title Last Reply Replies
Japanese beetles by lindal19460 Jul 14, 2019 1:02 PM 0
Where did you get the traps? by threegardeners Jun 19, 2016 6:11 PM 27
Thank you for using natural ways to get rid of your garden pests! by bennysplace Jul 18, 2012 1:40 PM 5
Beetle battle update by LarryR Jul 17, 2012 2:25 PM 5

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