Some of the organic gardening books I have say that these traps may actually be worse than not doing anything because you are attracting more bugs than you would have naturally. A product that works on smaller areas, like normal size yards is milky spore. It selectively attacks just the japanese beetle grubs. You have to apply it a few times a year to your yard for I think for 2 years to properly innoculate your soil. There are specific times of the year it has to be applied to be most effective. Then it is good for a while. Neem will decrease their damage. But you have to apply every few days. I have some hazelnut and apple trees that are completely defoliated from these little beasties.