Paste Application Brush Head with handle. The most efficient method of treating the exterior ground line zone of a standing utility pole is with a paste preservative and a round brush. Our special, synthetic fill brush heads, are 4 ½” diameter and are small enough to easily fit into the excavated area around the pole. Larger heads would require more excavation. Apply the paste to the 18” to 20” specified treatment zone while taking special care to dab preservative into the cracks and other physical voids. Most paste applications are 1/16” thick but you should always consult the preservative’s EPA label for actual application rates. Worn out brush heads slow the application so occasionally replacing the head will help your efficiency.