With the season just starting here in the midwest, I thought I'd share a homemade Japanese Beetle trap that works wonderfully well and is made out of items from your recycle bin.
Check out the tutorial for how to make one here.
A simpler trap version is to just knock the beetles into a container of soapy water. :-)
My gorgeous Fortex bean patch is being chewed on by Japanese beetles so I go out each morning and afternoon and grab my styrofoam cup that I leave in the garden. I roam the aisles and can see them on the leaves, usually in twos and threes. You have to put the container UNDER the beetles as you approach them since they'll fall downward through the leaves when disturbed unless they just fly away. But they seem to be so involved in their twosome or threesome that they'll hang onto each other and meet their watery grave together!
This year it's Japanese beetles and almost no Mexican bean beetles. Last year it was the reverse. The yellow fuzzy critters on the leaves are Mexican bean beetle larva and you can knock those into the solution as well.
Another option is to go after the grubs that are living in your yard (after they breed they deposit the eggs in the ground). Some options are nematodes, milky spore, and grub control chemicals.
Its not a sure fire method, but if more people would treat the grub stage, there would be less adult stage.
Its too bad they couldn't make a trap to just lure in the females...get rid of the females and the population will fall rapidly in the years ahead.
That is similar to the one I make. I put a bait in the top and cut holes for them to fly in and they can't fly out. I have killed thousands in previous years. You can't knock that many in soapy water. Last year I had less than 25 and this year have only seen three.
I have trapped thousand in recent years. I estimated 270,000 in '03. I have killed thousands more on wild grape vines, plum top growth, and on the edge of neighboring soybean fields. Also I have hand squished and also used a bit of Milky Spore....and prayed.
This year I have seen only a very few.