Answer: Borers will cut a double ring around the new tips of berry canes. Although I have never seen it on grapes, it is possible. To control it, cut off the tip below the girdling and destroy it by burning or put it in the trash to be removed. Continue doing this as long as you see the damaged tips. On a weekly basis, check your garden plants, surrounding plants and even wild plants in the area, too, beginning in late June and following through until September. The reason you need to keep doing it is that the borer lays its eggs in the cane and the larvae work their way downward over time, eventually reaching all the way to the crown. Pruning away the tip and the girdling should remove the borer and its eggs if you catch it early enough -- which is why you have to check so often. Good luck!
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