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japanese beetles

Posted by fiddlrs3 NE Illinois (My Page) on
Tue, Jul 22, 08 at 14:51

This is admittedly of the fringe of this forum, but probably an area of common interest for native plant enthusiasts. My showy trefoil, coneflowers, and beebalm, but especially my birch trees, wild plums, and ironwood have been devestated by an unbelievable swarm of japanese beetles.We cannot use our deck, since we have to sweep bodies and beetle poop off of it every 15 minutes, and the area around the deck is inches deep in their stinking rot. The only solutions I have heard are all poison sprays, and what's the use of having host plants for butterflies, finches, hummingbirds, etc., and then using non-specific poisons? On the other hand, I've put a lot of time, money, and care into my natives, and hate to see them devestated and my houses' shade gone from this plague. there a solution? The birds won't even eat them; I've watched them spit them out!

Follow-Up Postings:

RE: japanese beetles

There is a good chance that their larvae come from your lawn or a neighor's lawn and that they thereafter become flying, annoying beetles. In a lawn you can apply Milky Spore to help kill off the larvae and thus the next generation of flying beetles. I've noticed that many people on GW advise against the hanging traps since they attract the japanese beetles from far and wide and only kill a relatively small amount (the more mercenary people say to put the traps across in a neighbor's yard). I randomly found some info from U. of Kentucky at but it did not mention Milky Spore. Ohio State has some info on a wasp that parasitizes japanese beetles at You can buy Milky Spore in a lot of stores or via mail order. I don't think it's intended to be a fast fix but more of a fix in the long run.

Here is a link that might be useful: Milky Spore

RE: japanese beetles

I don't have the massive swarm that you have. And I've only ever a seen a few JB on my native plants. I have been treating my lawn with beneficial nematods, so that might be why I don't have many JB's?...

However at my friends house, I am watering her plants while she was away on vacation, she had a swarm of JB chowing down on her clematis.

I filled a small bowl with soapy water and knocked the beetles into the bowl. I let them set for a few minutes, before I dumped the soggy dead carcasses into the compost pile.

RE: japanese beetles

Unfortunately japanese beetles are generalists when it comes to eating. Therefore, they can easily enjoy eating native plants whereas native insects generally prefer the native plants they have come to know and love and don't bother a lot of non-native plants (there are some exceptions, of course).

I treat the adults by squishing them and the larvae by destroying them if I find them in/near the lawn. If I had a large infestation, I would certainly try the Milky Spore.

RE: japanese beetles

Thanks for the suggestions. I put down a systemic treatment around the two most damaged trees, and hope it doesn't get taken in by too many unintended hosts. The beetles have been dying off for days now, and the destruction of the main plants has slowed. I have several inches of carcasses around the deck now, so the smell is almost as bad as having the bodies and poop raining down. I also tried the milky spore, although in looking up some details, I found that my infestation is probably not from my own yard/grubs, but at least it feels like I'm doing my share in an environmentally unobtrusive way.

RE: japanese beetles

As disgusting as it is, those dead beetles would make a good addition to your compost pile or can be put on the soil to add a little protein. The milky spore is supposed to help with any grubs that are down in the ground now (or maybe they are more active about a month from now?) munching away on the roots of your grass and waiting to emerge to give you another bad day.

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