41 



It is my opinion that we are rushing into this enormously ex- 

 pensive campaign against the chestnut bark disease without con- 

 sidering as carefully as we should the chances of success. The 

 first question to consider is, can the disease be controlled by Met- 

 calf s and Collins' method, 3 of destroying advance infections and 

 establishing an "immune zone?" This is a technical question of 

 fundamental importance. It is a question to be answered by ex- 

 pert mycologists and plant pathologists. I have observed that 

 the leading advocates of the method avoid, as far as possible, dis- 

 cussion of its probable effectiveness. In Farmers' Bulletin 467, 

 the question is disposed of by inserting into the letter of trans- 

 mi ttal the following sentence : "The experimental data upon 

 which the recommendations contained in this publication are 

 based will be published in full in a forthcoming bulletin of the 

 Bureau of Plant Industry." The authors then go on to say (page 

 10) that "so far as tested" the method is practicable; and on 

 page 11, after giving an account of what they consider a success- 

 ful attempt to control the disease in the vicinity of Washington, 

 D. C., conclude with the following statement: "It is therefore 

 believed that this method of attack will prove equally practicable 

 in other localities and if carried out on a large scale will result 

 ultimately in the control of the bark disease." Up to the present 

 time the promised bulletin has not appeared and we are still in 

 the dark as to the nature of the "experimental data." I had 

 hoped that it might be presented at this meeting. In justice to 

 the public it should have been published before Bulletin 467. 

 There is great need of some real evidence that the disease can 

 be controlled. Apparently, the sole foundation for the optimis- 

 tic statements made by Metcalf and Collins in Bulletin 467 is 

 the result of the field test 2 which they made at Washington and 

 I hold that no definite conclusions can be drawn from that test. 

 The chief criticism to be made of it is that there is no means of 

 knowing what would have happened if the diseased trees had 

 not been removed. There was no check, and experimenters are 

 agreed that experiments without checks have little value. This 

 is one of the first principles of experimentation. Weather con- 

 ditions may have been unfavorable for the spread of the disease. 



