Effective protection against Japanese Beetles?
I am wondering if anyone has found an effective way to discourage Japanese Beetles from feeding on plants that they like? I mean, excluding any of the following methods: "biocontrols" of grubs (see other thread for comments), pheromone traps (counterproductive, increase beetle damage in their vicinity) highly toxic broad-spectrum insecticides such as Sevin (potentially kill beneficial insects), or replacing the vulnerable plants.
My restrictions would appear to leave "horticultural oils" such as Neem oil, and kaolin clay based products (physical barrier against insects, sold under trade name "Surround"), as possibilities. It should be possible to apply the product with a hose sprayer so that a small tree (10 to 15 feet high) can easily be treated.
Plants to be protected include Amelanchier "Autumn Brilliance" (small tree), Oxydendrum arboreum (small tree), Fothergilla "Mt. Airy" (medium shrub) and Clethra alnifolia (small shrub). The JBs go for foliage of the Amelanchier and Fothergilla (which have no flowers when the JBs are active), and flowers of the Clethra and Oxydendrum.
Here is a link that might be useful: Other thread on JB grub biocontrols