They seem to appear like alien crop circles in a British wheat field, mysteriously and overnight. Rows of holes drilled into the bark of your favorite nut tree. Some trees seem especially prone to this malady like this Stuart pecan tree (photo at left) growing near New Madrid, MO. The holes are typically conical in shape, wider near the surface of the bark and coming to a point at the bottom. Holes are drilled in near perfect rings around the trunk and large limbs. Many growers become alarmed when they see the holes and suspect an attack of wood boring insects. However, these holes are made by the yellow bellied sapsucker, a member of the woodpecker family (photo below).
Sapsuckers drill holes in the bark each spring to enable them to feed on tree sap that is flowing in the tree's trunk. Once these holes are opened, insects are also attracted to the tree's sweet sap and the sapsucker returns to the hole to feast on both insects and sap. Although the rings of holes look troublesome, sapsucker feeding does not affect nut production. In the world of nut trees, I have seen sapsucker holes in pecan, hickory, black walnut, and Persian walnut.