|About 2 months ago, my grape grower friend noticed "holes" in the main trunk of his grapevines. They are about 1/2 the size of a pencil eraser, extend about 1/16" into the trunk, and are about halfway up the trunk. The holes are in straightlines around the trunk. The "holes" fill-in (with sap?) within a day & you can hardly tell that the hole was there in the first place. He has applied pesticide for stem borers, which he had had a problem with before, but this has no effect on this new problem insect. What is this insect & what can be done to prevent it in the future?