DAMAGE TO CHESTNUT POLES BY INSECTS. 7 



wood-boring insects except to that portion near the surface of the 

 ground. Conditions of drainage are more important than different 

 soil combinations, and the condition of the soil is more important 

 than its composition; i. e., where the soil is hard packed there is 

 apparently less damage than where it is loose. The quality and con- 

 dition of the poles before setting is a very important factor to con- 

 sider before arriving at any conclusions as to the relative longevity of 

 poles under various conditions of site. Green (unseasoned) or im- 

 perfectly seasoned poles are less durable than those thoroughly 

 seasoned. Poles that are defective " before setting, as they very 

 often are (i. e., showing evidence of incipient decay), and poles that 

 have the heartwood mined by the chestnut timber worm, '' the work 

 of which is ■ very abundant, will, of course, decay much more 

 rapidly than poles that are in an absolutely sound condition. 

 The galleries of the chestnut timber worm afford an entrance to 

 the spores of wood-destroying fungi, and thus greatly accelerate 

 decay. White mycelium compactly filled these galleries throughout 

 many standing poles, thus clearly proving that these mines aid 

 greatly in enabling the fungous heart rot more rapidly and 

 completely to penetrate the entire heartwood of the poles. If the 

 injury by both wood-boring beetles and wood-destroying fungi 

 (between which there is a varying interrelation) be considered, then 

 in several lines from ten to twelve years old in North Carolina, 

 Virginia, and West Virginia at least 50 per cent of the poles are either 

 rendered unserviceable or their length of service is much shortened. 



ASSOCIATED WOOD-BORING INSECTS. 



It is not to be concluded that this wood-boring beetle is the only 

 insect that injures standing chestnut poles. Indeed, the most 

 common injury is by the "wood hce" or white ants.'' In lines from 

 ten to twelve years old these insects have seriously damaged as high 

 as 15 per cent of the poles, and their work is often present, at least 

 superficially, in as high as 75 per cent of the poles under all conditions 

 of site. However, the damage is usually to the outer layers of the 

 wood, where it is moist or there is incipient decay, and is more 

 superficial and locahzed than that of the chestnut telephone-pole 

 borer. Nevertheless, white ants often completely honeycomb the 

 sound heartwood of poles, especially at the base. They work both 

 in sound wood, "doty" (dry rot) wood, and "sobby" (wet rot) wood. 

 Sometimes a large channel runs up through the core of the heart 



a Sometimes this evidence is the old galleries of the destructive two-lined chestnut 

 borer {Agrilus bilineatus Web.), showing that the tree must have been dead before 

 it was cut for a pole, and hence is more likely to be defective throughout the interior; 

 in other instances heart rot is clearly present. 



b Zymexylon sericeum Saxi . " 



c Identified by Mr. Theodore Pergande of this Bureau as Termes flavipes Kollar. 



