An experiment in getting rid of Japanese Beetles organically

Two years ago I noticed something eating the grape leaves in our community garden. I was expecting the first fruit from it so I immediately investigated. I found a couple beetles and killed them. I thought I could control the problem if I stayed on top of it, but I did not know what they were or how much havoc they were going to raise in the next seasons.

After doing to my research and finding out they were indeed Japanese Beetles, I immediately started searching to find out if there were any organic ways to eradicate them. Apparently, when a Japanese Beetle or two first find you yard or garden and consider it tasty, they mark the territory to tell other Japanese Beetles, “Hey! Over here! This is a great Bed & Breakfast location! Check it out!” It’s all over from there once word gets out. They say if you catch those first few scouters and squish them, they won’t send out the signal, but I can’t see that being very effective. The only problem is there is only about a two month window depending where you live to try and squish all the beetles you can find, then they burrow into the ground after mating and the grubs that come after will eat eat eat grass roots and more until about June when they pop out to devour you beloved plants once again.

There were simple ways I found to try to lesson the population, like squishing them or collecting them into a bucket of kerosene… but the problem had persisted too long and had gotten out of hand for those means in the community garden. They had not only left a skeleton of leaves on the grape vine (apparently the veins don’t taste very good), they completely ate all the leaves off the rose bush, and devoured all the flowers that popped out on the hibiscus. It was time for these bugs to move on or suffer the consequences.

The next options for organic options included what is called white milky spores (or just milky spores) and predatory nematodes. Milky Spores sit there and wait for a Japanese Beetle grub to come along and ingest it. After that happens, it’s all over… That grub won’t make it out of the ground. They say every year after you introduce your milky spore you will see less and less beetles and after three years they will be gone! Then you have about 10 years of no beetles!! The spore will even naturally spread to other areas over time. It is most effective if you have neighbors (or even better, your community!) who also choose to use the spores, so their beetles won’t fly over to your garden to munch. Remember, they only kill grubs (baby beetles) not the beetle itself.

Predatory nematodes on the other hand are just that- predators. The seek out their food. From my research, they seem to be the most effective on the short term level, but it seems like they are easy to kill before they get a chance to get the job done. They have to stay moist, get onto moist soil in order to burrow and stay alive. They are microscopic so you won’t know you’ve killed them until you notice that nothing changed in beetle status the following season. So releasing them during the heat of the Summer would be a bad idea. They also die when their soil is frozen. Releasing them in the Fall or Spring is the best time, although if you expect your soil to freeze, I would think that releasing in the Spring would be the best. That way they would have all spring to feast on grubs, then all fall to feast on all the new grubs!

I plan on using both 🙂 Can’t hurt, they tell me. A couple weeks ago, I bought a 10 oz bag of organic St. Gabriel’s milky spore from Yard Garden Art. I picked them because they were a cool little co-op that I felt I should support. Although you can find the same thing through the actual brand name site for $10 cheaper, their customer service is A++! I highly recommend them! So when reading about this stuff on all the different sites, it talks about how easy it is, how it doesn’t harm anything, fine to use in veggie gardens, etc, etc… when I received it, the box told a different story. It was so scary! I read all four sides of the box. Warnings, cautions, don’t get it on your skin, wash your clothes and shower immediately after using, don’t let pets or children near, use on flower beds and ornamental gardens… said nothing about edible gardens!! Garden Yard Art’s customer service reassured me with stories from coworkers.

My e-mail:

Hello again :)
I just received
my box of Milky Spores, and after ready the box, I gotta say I'm pretty
intimidated! So, to build myself up again I have a few more questions:
Is it
safe to use on a garden you eat from? On one side of the box it says in big
yellow letters for use on lawns and grassy areas, ornamental gardens and flower
beds, mulched beds and ground cover beds....
Also, the active ingredient is
only .02%. What is the other 99.98% ingredients? That might be a question for
St. Gabriel's... And what does w/w stand for?

Their response (I had also asked about a product of their called “Grub Guard” in a previous e-mail, so there’s a blurb about that in here, too):

Hi Sarajoy,

It's wonderful to hear from you again! Sorry about the
intimidating box, but thanks for reading it, because again, these are very good
questions, and I went hunting for the co-worker who I knew had used it on her
garden, which is a mix of vegetables and ornamentals, and she is a grandmother,
so people of all ages are out and about in it, as well as pets (Her endorsement
of Milky Spore: "Look, it used to be when I dug out a hole for my tomato plants
every year, I'd see 30 to 40 grubs in the hole. The first year after I applied
the spore, I saw maybe 30 grubs, and it slowly reduced over time, but since the
third year, I haven't seen a single grub, and haven't had any problem with
moles. Now if I could only get my cat to stop feeling betrayed that he doesn't
have any moles to stalk").

So, in answer to your first question: Despite the
box not mentioning vegetable gardens specifically, it is entirely safe for
vegetable gardens. The bacteria in the power is only interested in Japanese
beetles and their grubs. You can eat it by the handful, if you like, have babies
roll around in it (I know it says that milky spore can be harmful if absorbed
through the skin, but no romping grandchildren were harmed in my co-worker's
garden, so I am pretty sure that you need *very* prolonged skin contact to be in
any sort of trouble), or have your dog play fetch with it, and no harm will come
to anyone--though you won't kill many Japanese beetles this way. Anyway, this is
a natural product, and can be set down anywhere.

As for the .02% active
ingredient, that is the beneficial bacteria, which is naturally microscopic. To
make it useful for someone who is putting it down, and give that bacteria a
place to call home while it's waiting to be used, the rest of the ingredients
make up the powder you see in the packets. Because the powder is so much bigger
and more weighty than the microscopic bacteria, it takes up a greater percentage
of the product. That w/w means 'weight by weight,' which is the scientific way
to say that these percentages are comparing the weights of the ingredients.
Basically, the 98.98% is just the powder, so you can actually apply the
bacteria, and it naturally weighs a lot more than the bacteria. 

If you would like way more information on what various abbreviations for solutions mean here
is a helpful guide:

To switch
topics to the Grub Guard that I recommended for fall application, my co-worker
(who has used it as well as the Milky Spore), reminded me that the South has had
some odd and severe winters that included unexpected freezing temperatures these
past couple of years. The autumn suggestion that I made would not be good if you
expect any kind of deep freeze in the winter. Grub Guard does not overwinter in
freezing temperatures--they live in the upper part of the ground, and so can't
survive if you get a serious frost line. It's a consideration I usually don't
take into account for anyone blessed to live near Georgia or further south, and
I'm sorry I didn't mention it when you first asked about Beetle

If you believe that the winter will be as cold and severe as it
has been for the last few winters, then I would hold off on purchasing Grub
Guard until the spring. Do you need any more questions answered? We're always
here for you.


Mari Customer

After being reassured (because even St. Gabriel’s website description stated the complete opposite of what their own box said!), I set out to the garden. You are suppose to put a teaspoon of dust every four feet by four feet on a windless day, then water. I chose instead to wait until the calm before the storm 🙂 You can buy what they call a “Lawn and Garden Dispenser Tube,” but I just used a measuring spoon that I never ever intend to use again. I’ll let you know in a few years what I notice about my Japanese Beetle population. I plan on buying some predatory nematodes to release come Spring. That will help BIG TIME I bet 🙂 I will share how that goes as well! Stay tuned!!

P.S. Sorry for the lack of pictures, I wanted to get this up tonight but forgot my pics at the shoppe… they will be up tomorrow though! Thanks!


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