Early in the spring the sapsucker tests many trees around its selected nesting site by making sample drillings before selecting ones it prefers. These trees, because of quantity or sugar content of the sap, are visited several times a day for the rest of the season and sometimes are used as a food source for several years. Feeding wounds serve as entry courts for a wide variety of wood decay or stain fungi and bacteria. Many forest trees are attacked high in the crowns, making light feeding wounds or sample drillings less evident. A condition known as black bark may develop which results from certain fungi colonizing the sap flow and discoloring the bark, and is good evidence that injury exists.
Black bands can develop on white birch as a result of a healing reaction to sapsucker injury.
To discourage sapsuckers from feeding on a favorite shade tree, wrap hardware cloth or burlap around the area being tapped or smear a sticky repellent material, such as bird tanglefoot, on the bark. In commercial forests or orchards, leave favorite feeding trees of the sapsucker untreated. Birds will concentrate their feeding activities on these favorite trees, which often protects nearby trees from serious injury. The Migratory Bird Treaty Act and Federal regulations promulgated under its authority prohibit shooting of sapsuckers. Shooting of this species would be an ineffective control anyway because transient birds tend to replace occasional losses to local sapsucker populations.