IQQ MISC. PUBLICATION 273, U. S. DEPT. OF AGRICULTURE 



the amount of space available so that neighboring living trees will 

 not be injured. If this precaution is not taken, the scorched trees may 

 draw in additional infestation and more or less nullify the effects of 

 the control work. 



The oil-hurning method 



Recent control technique has developed an economical method of 

 killing bark beetles in thin-bark trees, such as lodgepole pine, by 

 spraying the bark with fuel oiL firing it, and letting the bark be 

 scorched deeply enough so that the beetles will be killed by the 

 heat. The trees may be either felled and burned or burned in a 

 standing position. 



A fuel oil is used that has a high caloric content and burns evenly 

 and without too quick a flash. An explosive oil burns too quickly to 

 give good heat penetration. For burning standing trees a light oil 

 of gravity 32° to 34° Baume and a flash point of 160° F. has given 

 the best results. For burning trees on the ground ordinary fuel oil 

 with a gravity of 27° + Baume and a flash point of 225° F. has been 

 found most satisfactory because of its slower burning, greater heat 

 penetration, and lower cost. In either case from one-half to three- 

 fourths of a gallon is required to burn the average lodgepole pine. 

 The oil is applied with a hand pump through a long nozzle. 



With the burning-standing method, the oil is sprayed as high on 

 the bole of the tree as the equipment will permit, about 30 feet at 

 present, and the entire top of the tree is "crowned out" with lire. 

 The treatment is effective only to the height of the burn, and unless 

 the bole is thoroughly scorched as high as to a 6- or 8-inch diameter, 

 which is usually the upper limit of infestation, the tree must be 

 felled and the scorched portion burned with additional oil. When 

 lodgepole pine bark has been adequately burned to kill the beetles 

 underneath, the bark flakes will curl and show white on the edges. 

 Frequently when this method is used, the spotting and treating are 

 performed at the same time. A pack tra'in carrying the i^ressure 

 sprayers, oil, and felling tools follows the spotting crew, and in- 

 fested trees are treated wherever they are found. This method is an 

 economical one, and costs have averaged between 68 cents and $1.05 

 per tree. "\'\^iile the method is effective in ordinary weather it can- 

 not be used on windy or stormy days, and during dry or windy 

 weather great care must be used to avoid serious conflagrations. 

 This method is limited to the treatment of thin-barked trees such as 

 lodgepole pine, to trees of moderate height that can be burned as 

 high up as the infestation, and to situations where the fire hazard is 

 not too great. 



Lodgepole pine growing in dark Avoods or in dense thickets of 

 underbrush where the sun-curing method is not effective, or tall trees 

 which cannot be successfully treated in the standing position, can 

 be felled and burned with oil in places where decking and burning 

 in piles would not be feasible. A slow-burning fuel oil is used, and 

 the fire is carried along and confined to the bole of the tree by spray- 

 ing on oil from a hand pump. Two men follow, behind the fireman 

 and quickly extinguish any fire left on the tree or starting on the 

 ground. It is surprising in what hazardous areas this method can 

 be used without difficulty. 



