41 



It is mv opinion dial we are nisliiiig into tliis enormously ex- 

 pensive canipaii;!! a.i>ainst the cliestnvit bark disease williont con- 

 siderini^- as carcrnlly as we should the chances of success. The 

 first question to consider is, can tlie disease he controlled by Met- 

 calf's and Collins' method/ of destroying- advance infections and 

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

 fundamental im])ortance. It is a (question to l)e answered by ex- 

 pert mycologists and plant pathologists. 1 have observed that 

 the leading advoeates of the method avoid, as far as i)ossible, dis- 

 cussion of its probable effectiveness. In Farmers' bulletin 407, 

 the «(U('stion is dis[)os('d of by insert ing into the letter of trans- 

 mittal the following seidi'uce: "The experimental data u])on 

 which the recommeii<lations contained in this i)ublication are 

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

 liureau 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 NVashington, 

 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 l)ark disease.'' Uj) 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 

 lioix'd that it might be presented at this meeting. In jiistice to 

 the public it slioubl have l)een published before IJulletin 4(>7. 

 1 here is great need of some real evidence that the disease can 

 be controlled. Api)arently, the sole foundation for the optimis- 

 tic statements made by Metcalf and C'ollins in liulletin 407 is 

 the result of the tield test" which tlu'y made at Washington and 

 I hold that no delinite conclusions can l)e drawn from that test. 

 Tin; chief criticism to be made of it is that tliei-e is no means of 

 knowing what would have hap])ene(l if the diseased trees had 

 not been removed. There was no check, and ex])erimenters are 

 agreed that experiments without checks have little value. This 

 is one of the first ])rinci])]es of experimentation. Weather con- 

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



