28 



When it becomes necessary to undertake direct control measures, the broods 

 in the bark of the infested trees can be destroyed by whichever of the following 

 methods are best suited to local conditions: 



Floating the Logs. Where water is available, the simplest method is to cut 

 the infested T ogs during winter and float them as soon as cut or as early in the 

 spring as possible; this will kill the greater part of the broods in the bark. 



Sawing in Winter and Burning the Slabs. Where it can be done pro- 

 fitably, the infested logs may be sawn during winter, and the slabs, which will 

 contain the brood, burned before the spring opens. 



Barking the Trees. It is always possible to fell and bark the infested trees 

 during winter, and when necessary, to burn the infested bark before spring 

 opens. The presence of the greater number of the grubs in the middle layers 

 of bark renders burning the bark necessary in the control of outbreaks involving 

 the Western Pine Bark-beetle. Control operations should be completed usually 

 during the period between the first of November and the following June, but 

 the work should be finished as early in spring as possible. 



When it is not possible to utilize the timber profitably, and control measures 

 are necessary to protect valuable holdings against ravages of the beetles, the 

 infested timber should be treated by the cheapest effective method so as to des- 

 troy the contained broods. The infested trees may be cut and burned or 

 thoroughly charred before spring opens, frequently at less expense than by re- 

 moving and burning the bark. 



It will often be best to combine two or more of the available methods in 

 order to complete the control work during late fall, winter and early spring. 



This control work has reference solely to the freshly infested trees, with 

 green, yellowish, or moderately reddened foliage, having the bark filled with 

 the beetles and their grubs, and not to the old " red-tops " which have been 

 dead for one and a half years or longer, and from which the beetles have 

 emerged. 



Trap-trees may be utilized in the control of some species. The importance 

 of slash burning in bark-beetle control and the possibility of utilizing it as a 

 trap has already been mentioned. 



THE INTERRELATIONS BETWEEN FIRE AND BARK-BEETLES. 



It has been shown that ground fires which injure and kill such large numbers 

 of trees may provide material for the rapid development of bark-beetles. This 

 is particularly true if the burns succeed each other year after year in neighbouring 

 localities. This relation between fires and beetle development has probably 

 always obtained, since fires have occurred in our forests for ages through the 

 action of lightning and the agency of man. 



When fires run through infested slashings, immense numbers of beetles 

 may be destroyed and the fire may be very beneficial from that standpoint. 

 When light fires run through beetle-infested timber the greater part of the broods 

 are not affected by the heat, since only the bases of the trees are burned. If 

 the fire is very hot so that the trees are burned far up the trunk, many of the 



PLATE 7. 

 BARK-BEETLE BREEDING GROUNDS (ORIGINAL). 



Fig. 1, Beetle-killed timber, a clump of red-top yellow pine near Princeton, B.C. 



Fig. 2, Tunnels of Dendroctonus borealis, at base of white spruce in Jasper Park, Alta. 



Fig. 3, Tunnels of Trypodendron bivittatum in white spruce, Jasper Park. 



Fig. 4, Work of woodpeckers on a beetle infested yellow pine, Coldwater Creek Valley, B.C. 



