I planted new grapevines - seedless Reliance, Mars, and Marquis varieties -...
I planted new grapevines - seedless Reliance, Mars, and Marquis varieties - in our garden (in full sun) this spring. A couple of weeks ago, I noticed that the leaves are being eaten(?) by something. It seems to be getting worse over time. Last pic is a bug I found on one of them, but the damage looks more like worms/larva of some sort. I will probably have to spray them, but would like to know what I'm possibly dealing with before doing so. Any help would be appreciated!
the damage to your young grape leaves is caused by beetle feeding, possibly a rose chafer. The larvae of these beetles overwinter as grubs in the soil and after going into pupation in the spring, emerge in late spring as adult beetles. It would appear that your grape leaves were the first vegetation they encountered as they emerged. Unless there is some other damage to the roots or stems, the vines should continue to grow.
It's too late to apply any control methods.
Thanks for the information. After asking around, the culprit appears to be something called a "grape rootworm" which matches the damage pattern and the bug I saw. Unfortunately, the larvae appears to target the roots (as the name suggests) and needs to be controlled by killing the adults. I had had a different variety of grapes in this same spot before replanting, so it is possible the larvae were left over in the soil from that period, despite mulching.