Nearly every other day, I've been picking Japanese
Beetles off our grapes, brambles, and cherry. Sunday morning,
I started to notice that our Japanese Beetles are showing a definite
preference for the thinner, entirely green leaves of our yellow grape
(which I thought was Golden Muscat, but now am not so sure about)
compared to the thicker, white-undersided leaves of Steuben. In
fact, only a few of the Steuben grapes had been touched.
Turns out that the distinction isn't just in my garden. This
Ohio Extension Service factsheet notes that the thin leaves of
French hybrid grapes (bred from a mixture of European and American
ancestors) are far more susceptible to Japanese Beetle damage than are
the thick leaves of American grapes. Steuben is a perfect example
of an American grape while our yellow grape is probably a French
hybrid. This page
gives a longer explanation of the two types of grapes, if you're
interested.
Since I actually prefer the purple fruits of Steuben to the yellow
fruits of the other grape, I'm tempted to pull out the latter in favor
of the former. For now I'll let the yellow grapes grow, but I
think I'll start considering them to be expendable.