Japanese Beetle season is over - thank goodness - but I wanted to share my personal experience with this curse.
I have numerous rose bushes, raspberry bushes and a multitude of perennials and annuals. Last year I got hit with the first onslaught of these pests and after most of my roses had been attacked I resorted to what seemed logical, I put up a Japanese Beetle trap. Then I heard from everybody how that was exactly the worst thing to do, that now I was attracting even more to my yard and I should kiss all my flowers goodbye. I did collect a fair amount of beetles but by then the damage had been done.
Fast forward to this year. When the beetles began to hatch it didn't take long to notice the damage. Leaves eaten through although nothing had yet bloomed. It wasn't unusual to kill 15-20 per day! This time I was ready - I put up not one, but two traps. The result? Within a month I had to replace the bags. Yes, they attracted lots of beetles - and frankly, that's what they are supposed to do. I did myself, and my neighbors, a great service. I don't know how much a beetle weighs but the combined weight of two bags was just short of four pounds! That's a hell of a lot of beetles. (The replacement bags are just as full now)
So, with all these beetles that I brought into my yard I suppose you think the effect was utter and total disaster. On the contrary, the daily count immediately dropped to 4-8 beetles, easily managed by pinching them (probably 1 out of 5 got away) or, my favorite, zapping them with a quick shot of insecticide spray (don't cringe, it works marvelously, none get away and the use was probably less than two teaspoons all year! And I really think the bees were thankful because the beetles rarely got to the flowers).
Yes, some of my roses suffered. Interesting was that some of them were real attractants and some of them the beetles left completely alone. But in the end I enjoyed a lot more than I had the year before. An interesting sidelight - I had no aphids this year and that I don't understand unless it had something to do with a very late freeze we had.
Next year I'm going to apply a pre-emergent spray to the lawns - and hang the beetle traps. Maybe between the two I might get even better results.
The bottom line? Beetle traps work.