386 PRINCIPLES AND PRACTICE OF PRUNING 



not increase the strength of the trunk or limb to the extent that is 

 generally supposed. 



291. Dead or diseased branches. For the work of removing 

 branches, the most essential implements are a good-sized saw with 

 teeth so set as to make a wide cut, a gouge, a chisel, a mallet and a 

 strong knife. For cutting limbs near the ground these are the only 

 necessary implements. For limbs situated elsewhere a ladder may 

 be needed; also, at times, a rope. 



292. Treatment of cavities. During the last few years there has 

 been widespread popular interest in the treatment of decayed places 

 in old trees. This type of work comprises many inquiries addressed 

 to the Department of Agriculture and refers solely to methods em- 

 ployed in cementing cavities. This is a logical result of the present 

 extensive essential operations: (1) Removing all decayed and dis- 

 eased matter, (2) sterilizing and waterproofing all cut surfaces, and 

 (3) filling the cavity in a manner that will favor rapid healing and 

 exclude rot-producing organisms. 



The necessary tools for digging out decayed matter are two out- 

 side-ground socket-handled gouges (one with a curved cutting edge 

 of about s/4 inch, and the other perhaps l l / 2 inches), a chisel, a 

 mallet, a knife and an oilstone for ordinary work. The gouges, 

 chisel and knife should never be used near the cambium when they 

 lack a keen edge, as dull tools will injure it. In cutting out deep 

 cavities, longer interchangeable handles for the gouges may be nec- 

 essary. A ladder or a stepladder will be required if the work is 

 more than 5 feet from the ground. 



293. Excavating. Usually an old decayed spot may be partially 

 or wholly covered by a new growth of wood and bark at the edges, 

 and the visible decayed area be small as compared with that which is 

 hidden (Fig. 301 D, F). In such cases it is usually necessary to en- 

 large the opening with the gouges and mallet in order to make 

 sufficient room in which to use the gouges in the interior. This 

 opening should not be any wider than necessary, but it may be 

 sufficiently long to reach all the decayed and diseased heartwood 

 with little or no additional injury to the tree. 



If the decayed and diseased wood extends some distance above 

 or below the external opening, it is a common practice to cut one 

 or more holes above or below the main opening in order to facili- 

 tate the removal of the diseased wood (Fig. 305 A). This results in 

 one or more bridges of wood and bark spanning the long interior 

 cavity, a practice of doubtful value, partly because it is often im- 

 possible to see whether the diseased wood has been entirely removed 

 from the under side of the bridges, but mainly because there is a 

 strong tendency in most trees for the bark and the sap wood of the 

 bridges to die and decay as a result of severing the sap-conducting 

 tubes both above and below. If the holes are pointed above and 

 below, there is less trouble from this source. A practice that permits 

 a more thorough cleaning out of the cavity is to make a narrow 

 opening, pointed at both ends and sufficiently long to include all the 



