Japanese Beetles are a nuisance for anyone East of the Mississippi River trying to grow roses or other fragrant flowers. They can kill a small rose bush in an afternoon, and they seem to be immune to any season-long insectides you'd want around roses. While I suspect that the Japanese Beetle traps, like bug zappers, may draw as many bugs as they kill, I can't resist the temptation to rid the world of as many of these horrid little beasties as I can.
Several companies sell excellent traps for the pests, including Sterling, SpringStar, and others. And they charge $5 or so for refill bags. Of course, this drops down to 50¢ in the fall, on closeout, which you then have to store the bags all winter. But you already have an endless supply of Plastic Grocery Bags (PGBs), so why should you buy more bags?
By curling the handles and the opening of the PGB inward, you can hook the bag onto the Japanese Beetle trap made by one of the nice companies listed above. Make a loop of a 6-inch piece of wire or twist-tie, girtling the bag with it to give about a 2-inch opening. If you run out of attractant, put a drop of honey (or cut flowers if you have a lot of bees around) in the bottom of the bag. The first bugs will find the nice-smelling honey, and after that the others will be attracted by the smell of other bugs. When the bag gets full (or starts to smell bad), knot it closed and let it sit in the sun to kill all of the bugs.
A Q&A from Gardens Alive doesn't speak highly of traps, but it has some great suggestions for dealing with Japanese Beetles, including ways to attract birds (who apparently eat them) and using beetle juice to repel the bugs. I don't know. We have about a dozen active bird houses around our house, and still every year I get to slaughter Japanese Beetles by the thousands.
And that beetle juice sounds fun to make.
This year, I didn't put any traps out. The difference is that the finches who live in our bird houses have found the rose bushes, and patrol them regularly. Finches love to eat Japanese Beetles! Yay!
Whether it's the finches, the lack of traps attracting them, or some downswing in the beetle population, our roses have not been hit by the beetles this year.