22 



By counting the trees attacked in each year in each of a sufficiently large number 

 of clumps of " red-tops," and estimating the annual percentage of newly-infested 

 acreage it is possible to arrive at a fairly definite estimate of the rate of spread. 



Mr. H. H. Thomas and Mr. J. B. Gareau, of the Provincial Forest Branch, 

 have been in close touch with the outbreak about Princeton, and have made 

 careful and valuable observations during the late sum ner and fall. Counts of 

 the infested trees in and about five isolated clumps of red-tops, made by them 

 after the flight of the beetles was over, gave the following results: 



It is found that about some clumps of red-tops there are no trees attacked 

 this season, indicating that many 01 the beetles emerging therefrom this summer 

 had migrated some distance. In other places streaks of recently infested timber 

 are found at some distance from any red-tops, and isolated groups of red-tops and 

 isolated trees are frequently seen. Many of the emerging beetles migrate in 

 swarms to some distance and thus either increase the number of the clumps, or 

 settle about those already started. It will be seen that in the five typical instances 

 detailed above, the number of infested trees has increased from 10, in 1911, to 

 139 in 1913. Mr. Thomas considers a conservative estimate of the annual 

 increase in acreage infested at approximately one to three. 



POSSIBILITY OF NATURAL CONTROL. 



Bark-beetles are preyed upon by various parasitic and predaceous insect 

 enemies which destroy the eggs or brood, as well as by fungous diseases. Insect- 

 feeding birds help to some degree in keeping down their numbers. There was no 

 indication of any effective natural control in connection with the Princeton out- 

 break. 



RECOMMENDATIONS FOR THE CONTROL OF AN OUTBREAK SUCH AS THAT AT PRINCE- 

 TON, B.C. 



When bull pine is found dying as isolated trees and clumps of trees, with the 

 foliage fading during winter and turning red in early summer, with the 

 bark of these trees filled with bark-beetles and their grubs, and the trunks 

 studded with gum-tubes, a more or less serious bark-beetle outbreak is indicated. 

 Before control measures are adopted a forest entomologist should be consulted 

 for the exact determination of the species concerned; for the details of the control 

 measures will depend upon the life-history and habits of the beetle or beetles, 

 and the reaction of the trees to their attack. 



The infested area should be cruised for dying trees, and the infested trees 

 (containing the broods) marked for cutting. If the area is extensive, a rough 

 map should be made to locate the badly infested parts. The trees may be 



