36 SOME INSECTS INJURIOUS TO FORESTS. 



DISEASE AND SAP FLOW. 



Dead larvae are frequently found in the mines, covered with white 

 flour-like spores, and sometimes these spores are so common that a per- 

 ceptible cloud rises from the wood when it is split open. Experiments 

 in placing some of the spores with healthy uninjured larvae in bottles, 

 as well as with those in the normal position in the wood, resulted in 

 the death of the larva? and the development of apparently the same 

 disease, while the duplicate larvae kept under the same conditions, but 

 without contact with the spores, remained normal and healthy. 

 Therefore this is a fungus which will kill the borers and one which is 

 evidently of considerable importance. 



The profuse flow of sap together with a gummy substance in the 

 wounds made in the living bark and cambium is evidently detrimental 

 to the normal progress of the young larvae and apparently many of 

 the latter are thus destroyed. 



METHODS OF CONTROL. 



It should be remembered that all the holes found in a tree and all 

 other damage by the borer are not the work of one generation, but 

 usually that of repeated annual attack during the life of the tree; 

 also, that a burrow in the sapwood of a young tree remains the same 

 burrow in the heartwood of the old tree, without change, as long as 

 the tree exists, except in the healing of the original entrance. The 

 number of borers and the annual amount of damage is not so great, 

 therefore, as might appear, and, while each female is capable of depos- 

 iting a hundred eggs, only a small percentage of the larvae hatching 

 from them survive the bark-infesting stage or complete their develop- 

 ment to adults. This suggests that any method of management which 

 will insure the destruction of a large per cent of the surviving larvae 

 and beetles each year will reduce the damage to a point where there 

 will be practically no loss. 



With our knowledge of the life history and habits of the insect it 

 is now possible to make definite recommendations and suggestions for 

 its control. Some of those of immediate practical importance are as 

 follows: 



TIME TO CUT LOCUST TO DESTROY THE YOUNG LARVAE. 



The cutting of locust for all purposes, including thinning operations 

 and for private or commercial use, should be done during the period 

 between the 1st of October and the 1st of April, the bark removed 

 from the crude product, such as posts, poles, and the like, and the 

 tops and thinnings burned. The removal of the bark from all desira- 

 ble portions of the trunks of the trees felled during this period is 

 important and necessary in order to destroy the larvae before they 



