Circular No. 134. '••^■'ut-'i March 7. rjii. 



United States Department of Agriculture, 



BUREAU OF ENTOMOLOGY. 

 L. O. HOWARD, Entomologist and Chief of Bureau. 



DAMAGE TO TELEPHONE AND TELEGRAPH POLES BY 

 WOOD-BORING INSECTS. » 



By T. E. Snyder, 

 Agent and Expert. 



It has recently been determined through special investigations con- 

 ducted by the Bureau of Entomology, in cooperation with telephone 

 and telegraph companies, that serious and extensive damage is being 

 done in certain localities to standing poles by wood-boring insects. 

 The object of this circular is to give information on the principal as 

 well as other types of insect injury to poles, so that line inspectors 

 may distinguish the various types and determine and report on the 

 character and extent of the damage. 



CHARACTER OF THE IX.JURY. 



The principal injury to the poles consists in large mines in the wood 

 near the line of contact with the ground, necessitating the frequent 

 resetting or even the replacement of the damaged poles. These 

 irregular mines (fig. 1) run both transversely and longitudinally 

 throughout the heartwood, and are sometimes 7 inches long, but 

 vary in length. This injury is usually in the outer layers of the 

 wood for a distance of from 2 to 3 feet below and sometimes from 1 

 to 2 feet above the line of contact of the pole with the surface of the 

 ground. The greatest damage is to that area just below and just 

 above the surface of the ground; here the conditions of air and 

 moisture are most favorable. The mines, often very close together, 

 completely honeycomb the wood in a zone from 3 to 4 inches in from 

 the exterior of the poles (fig. 3); this so weakens the poles that they 

 break off close to the surface of the ground. The basal 2 feet is 



' Revised extracts from Bulletin 94, Part I, Bureau of Entomologv, U. S. Department of Afrriculture, 

 1310. 



77538°— Cir. i:{4— 11 1 



