4 INSECT INJURIES TO FOREST PRODUCTS. 



Construction timbers in bridges and like structures, railroad ties, 

 telephone and telegraph poles, mine props, fence posts, etc., are some- 

 times seriously injured by wood-boring larvae, termites, black ants, 

 carpenter bees, and powder-post beetles, and sometimes reduced in 

 value from 10 to 100 per cent. 



PREVENTION OF INSECT INJURIES TO FOREST PRODUCTS. 



The problem of artificial control and prevention of insect injuries 

 to forest products offers less difficulties perhaps than that relating 

 to many other branches of the general subject of forest-insect control. 

 In most cases the principle of prevention is the only one to be con- 

 sidered, since the damage is done soon after the insects enter the 

 wood, and therefore it can not be repaired by destroying the enemy. 



Crude Products. 



The proper degree of moisture found in the bark and wood- of 

 newly felled trees, saw logs, telegraph poles, posts, and like material, 

 cut in the fall and winter and left on the ground or in close piles 

 during a few weeks or months in the spring and summer or during 

 the period when the particular species of injurious insects are flying, 

 are some of the conditions most favorable to attack. The period of 

 danger varies with the kind of timber and the time of the year it is 

 felled. Those felled in late fall and winter will generally remain 

 attractive to ambrosia beetles and adults of round and flat headed 

 borers during March, April, and May. Those felled during the 

 period between April and September may be attacked in a few days 

 after they are felled, but the period of danger from a given species 

 of insect may not extend over more than a few weeks. Thus certain 

 kinds of trees felled during certain seasons are never attacked, while 

 if they are felled at other times and seasons the conditions for attack 

 may be most favorable when the insects are active, and then the wood 

 will be thickly infested and ruined. The presence of bark is abso- 

 lutely necessary for successful infestation by most of the wood-boring 

 grubs, because the eggs and young stages must occupy the inner 

 and outer portions before the latter can enter the wood. Some 

 ambrosia beetles and timber worms will, however, attack barked logs, 

 especially those in close piles or otherwise shaded or protected from 

 rapid drying. A large percentage of the injury to this class of 

 products can be prevented, as follows : 



(1) Provide for as little delay as possible between the felling of the 

 tree and its manufacture into rough products. This is especially 

 necessary with trees felled from April to September in the region 

 north of the Gulf States and from March to November in the latter,. 



[Clr. 128] 



