I often get questions regarding holes in trees, especially pecan trees. The holes are not random, but rather in straight lines. I wrote an article on this a couple years ago for the Oklahoma Pecan Growers Association newsletter (Stafne, E.T. 2010. Trunk damage from sapsuckers: Cause and effect. In: M. Smith (ed.). OPGA newsletter vol. LI no. 2:1-2.)
Here is the text:
Have you ever noticed certain pecan trees with holes? Lines of holes in perfect rows, row after row? The cause is not always obvious. Holes like these are caused by one thing, but may be confused for another. Wood borers are often blamed, yet they do not possess the acumen to make the holes into perfect lines. Holes in perfect lines are most definitely caused by another creature – the Yellow-bellied sapsucker (Sphyrapicus varius).
Sapsuckers are close relatives to woodpeckers. They overwinter mainly in Mexico and Central America and spend the summers in the U.S. and Canada. Oklahoma is directly in their migratory pathway and pecans are one of their preferred food sources. The birds are about 7 to 8 inches long with a black head and a white stripe extending down its neck. The yellow-bellied sapsucker has a red forehead with some pale stripes on the chest with a black border to the throat area. Its back is black with white bars and has black wings with some white as well. The yellow breast (or belly) fades to a creamy white from front to rear. The tail is often black with white bars.
It is often thought that the birds are after insects under the bark. While this might be true in some cases, they are more likely after the tree sap that exudes once the bark and wood have been penetrated, hence the name sapsucker. The damage caused by the holes themselves is minimal; however, those holes can be entry points for fungi and bacteria (Photo below). Numerous holes on the same tree may actually weaken the trees, causing stress and susceptibility to other maladies. Rarely, the tree may be girdled if an excessive amount of holes are made that surround the entire trunk.
Control of the sapsucker is not easy. Sapsuckers are a migratory, non-game bird and are protected by federal law. Options for control can include exclusion by wrapping the tree trunk with burlap or other material to discourage the birds from returning. Another option is frightening techniques like visual or sound devices. Sometimes, however, these deterrents do not work or work only for a short period of time. Tactile repellents such as Tanglefoot may be another option to discourage landing upon the trunk.
Above all, one should remember that unless the damage is severe, the tree will likely show little or no problems. It may be best to just let these elegant creatures have their nourishment from a few of their favorite pecan trees and for us to learn to live together in harmony.