Q: I found this growing on a wild grapevine off my deck in late summer at my cabin in Rabun Gap. Very curious looking spikes.

A: They are grape tube galls. They are caused by a small flying insect called a midge. Adult midges lay their eggs either on the backside of leaves. Orange, maggot-like larvae hatch from the eggs and enter the leaf tissue.

The larvae secrete hormones that affect how the leaf tissue grows: like a horn in this case

Truthfully, not much damage is done to the grape vine so no control is needed.

If you’re curious, use a sharp knife to split some of the galls to see what’s inside. If you open them before the insects emerge from the gall, you’ll see yellow immature insects inside.

Grape Tube Galls