Home > Great Big Greenhouse Blog > June 2014 > GARDEN TALK with DOUG - JAPANESE BEETLES ARE EMERGING


The best defense in fighting Japanese Beetles is knowledge.

The best strategy in eliminating, or at least, reducing the damage done by Japanese Beetles is through learning the life cycle and applying control measures at the appropriate times.

                Right now the Japanese Beetle is in the pupation stage of life and is emerging out of the soil to feed on plants.  I recommend a three different strategies at this point.  First, spend time outside and handpick the beetles off the plants and bag them.  The more you handpick then the less egg laying will occur which will reduce the number of larvae (white grub worms) which equals reducing the population and damage.   A second strategy is to place Japanese Beetle traps, with bait, in a remote area in order to lure them away from your plants.  Both these strategies are effective and environmentally friendly.  A heavy infestation may require insecticidal spraying.  I strongly recommend BONIDES CAPTAIN JACK’S DEADBUG BREW.  The main ingredient is SPINOSAD.  Spinosad is an environmentally friendly, certified organic product.  Captain Jack’s Deadbug Brew is toxic to a wide variety of chewing insects, including Japanese Beetles, and relatively non-toxic to mammals and beneficial insects, such as our bees, lady bugs, and praying mantis.

                While the Japanese Beetles are out and about, they will mate and lay eggs.  In August these eggs will hatch into larvae that will move to the soil.  This larvae stage of the beetle is called the white grub worm.  September is the month for the best control of Japanese Beetles.  You want to apply a product called Milky Spore to the soil.  The larvae will ingest the milky spore and die and, at the same time, will help multiply the amount of milky spore in the soil for even more control.  Milky Spore is also a very environmentally friendly product.  You want to kill as many of these white grubs at this time before they go down deep in the soil for the winter.  Then in late February and early March you will want to reapply Milky Spore for further control of the white grub worm.  Keep in mind that early spring is when the white grub worm works its way to the surface and feeds on grass roots, thus damaging our turf.

                My overall battle strategy is for you to do some handpicking,  place beetle traps in remote areas, spray the adult beetle with Captain Jack’s Deadbug Brew, and spread some Milky Spore in September and again in late winter.


Posted: 6/21/2014 by Doug Hensel | with 5 comment(s)
Mark Bliss
Oops, one final note, they do love my hardy Hibiscus.
And I am having trouble finding replacement lures for my J-Beetle traps.
7/5/2014 6:58:24 PM

Mark Bliss
Oh, and just a note, I have NEVER seen any J-Beetles in my Boston Ferns! And I have a bunch of ferns hanging on my porch every summer.
7/5/2014 6:54:37 PM

Mark Bliss
Catherine, the traps I have had success with are basically a yellow plastic "vane" and a replaceable bag that hangs below, combined with an attractant. The bugs fly in, fall into the bag and cant get out.
Note that the bags need to be emptied regularly and many bugs will be alive. Dump them into a zip-lock bag and dispose of them. If you neglect to do this you get a bag of dead bugs, combined with rain water and, well, nasty odors.
The traps are commonly available, but you may find a shortage due to seasonal high demand.
Stores have them in stock Doug?
7/5/2014 6:49:24 PM

Thank you for this straightforward and helpful advice on dealing with Japanese Beetles!
7/3/2014 8:08:05 PM

Catherine miller
What in the world is a Japanese beetle trap?
Otherwise thank you so much for the information
We have boston ferns on our patio and they love them.
7/3/2014 2:28:04 PM

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