Interesting article. However, I'm with you on still not using this per one of the comments below the article .."I tried your suggestion, and I regret it. The cedar oil discolored the leaves of my tree, made the young branches wilt and the leaves are turning brown (I just hosed them down to help get rid of some of the cedar oil). It didn't repel the beetles at all either. My poor trees, I hope they recover. Those Japanese Beetles are a real pain in the butt. They are defoliating all of my deciduous trees".
I don't have roses or my Redmond Linden anymore (2 of their favs) so I will continue with the bucket trick. The did totally shred my Cuphea ignea so no harm to most of my Hummer plants. 'Vermillionaire' was attacked good only for a couple of days recently but it is still in good condition & didn't see any on it for the past 3 days.
They started with my Plum tree which was covered & also saw a few on my Black Chokeberry, which always is a medium attractant. Didn't see them on my Quince which was used quite heavily in the past.
BTW, I didn't know Salvia was in the mint family. Smells like it should be in the skunk family ha ha. Never saw a JB on my Monarda or Catmint for that matter.