The don't eat natives. They like the roses, I don't know where their lineage is, I know some are Canadian and the multi-flora seems native??
They do not eat any native plant in my border!
Plants not touched:
Tomato Pepper Rudbekia Phlox Iris Daylily Annual vinca Pansy Petunia Viburnum Heuchera
Lily of the Valley Honey Locust Seven sons flower Peony Canna Begonia Mint Potentilla Sedum Evergreens
Ornamental Grasses Clematis Lilac Echinacea
The odd thing is, they do nibble on the zonal geraniums, but I find them dead under those! In the garden center, the geranium hanging baskets had a row of dead Japanese Beetles under them. Nowhere else did this happen. Then, the same thing happened at home. I found them dead inside the geranium pot and around the outside of it.
So, I looked around the internet for some more clues.
It's pretty simple: Scientists at the U.S. Department of Agriculture have determined that the flower petals of the common geranium can be deadly to the Japanese beetle.
In experiments at the USDA's Agricultural Research Service in Wooster, Ohio, within 30 minutes of consuming red, white, or salmon geranium petals, the beetles rolled over on their backs, legs and antennae slowly twitching, and became paralyzed.
They recovered within 24 hours, but here's the beautiful part:The USDA is working on a patent for a spray based on the geranium.
Were this to happen outside the lab - say, on a golf course, in fields of corn, soybeans, or grapes, or in backyard gardens - the immobilized beetles likely would dry up, rendering them easy prey to ants, birds, toads, and moles. from: http://articles.philly.com/2010-04-30/news/24957098_1_beetles-geranium-pest/3
It's like the crack cocaine, they eat the geranium and become drunk and paralyzed, falling on their backs, unable to move. Scientists have studied this and noticed that even when "healthier" beetle options were close, they couldn't stop themselves, returning over and over, and getting polluted and eventually dying.
Another interesting beetle fact: Japanese Beetles attract other Japanese Beetles. If you can get out in the middle of July and knock the first wave down, either by the soapy water method or Sevin, you can certainly effect the future numbers of these devils.
So next year, when picking annuals, remember: Geraniums are the death of Japanese Beetles!!