36 



CONTROL MEASURES. 



Serious outbreaks by this beetle may evidently be controlled by the 

 destruction of the broods during the winter months, by any of the methods 

 already recommended. If water is available, the infested logs should be cut 

 and floated between November and the last of March. The infested logs 

 may be cut during the fall and winter, sawn during the winter and the slabs 

 burned before April. The infested logs may be barked between November 

 and the middle of March and the logs left for later sawing. The removal of 

 the bark from the lower and middle trunk of over three-fourths of the infested 

 trees in a district should suffice to bring ttiis insect under control. It is not 

 necessary to burn the bark. 



It is probable that where cutting is carried on during winter, spring or 

 early summer, the stumps, logs and slash will attract the beetles and protect 

 the green timber. Slash-burning between the first of October and the first of 

 March, should prove an efficient control. 



Trap trees might be used with advantage in control of outbreaks in valuable 

 holdings, at a distance from cuttings. A few trees to the acre cut in the infested 

 area during late winter or early spring should attract sufficient beetles to protect 

 the surrounding timber. These trees must be treated during the following fall 

 and winter so as to destroy the broods contained in the bark. 



AMBROSIA BEETLES. 



These insects, also known as Timber-beetles, or Pin-hole Borers, are small 

 elongate wood-boring beetles, which excavate round black tunnels, the diameter 

 of a pencil lead, for several inches into the wood of dying trees, logs or stumps. 



Fig. 19 Gnathotrichus retusus Lee.; The Douglas Fir 



Ambrosia-beetle. Greatly enlarged. 



(Original) . 



The species found in British Columbia confine their work to the outer seven 

 or ten inches of the wood, but frequently ruin that portion of the logs for all 

 valuable purposes. 



