what are effective, non-chemical, ways to control japanese beetles?

Question

I'm beginning to see adult Japanese beetles on my dahlias and other flowers. It doesn't look like a heavy infestation but I am wondering what are some non-chemical control methods. I've read that nematodes are one option. Are they effective? Are there others?

Answer 1

Milky Spore is another option. Apparently, it is very effective for some, not at all for others. I hear it is most effective if you can convince your neighbors to use it, as well, so a larger area is infected with the disease (which kills the grubs).

I put it down in my yard two years ago, as did a few of my neighbors, and I have noticed less beetles since, HOWEVER I put it down at the end of a boom season for the beetles (they almost completely defoliated all of the linden trees in the town I live in and the neighboring town, too), and I notice less damage all around. We had a record-breaking drought last year, too, which I'm sure killed a lot of the grubs. When I dig in my yard, I'm not finding many grubs at all, and have found none that appear to be infected, so I have no evidence that the milky spore is doing anything. I think we may be at in a "bust cycle" following the boom. I'll be interested to see how many beetles we have in a few years.

For smaller numbers of beetles, I hand pick into a bucket of soapy water. That seems to reduce the amount of damage I see in my yard, but during the boom year it was hopeless.