n 



J I is iiiv (t])iiii()ii iliMi \\<' arc nisliiiiii iiilo lliis ciioriiujii.sly ux- 

 peii!si\i* caiiipaij;!! a.uainsl ilic (•licsiimi haik disease without cou- 

 sidci'iiiii as carcrullv as we should the chances of success. The 

 lirsi (juesl ion 1(» consider is, can 1 he <lisease h«' conii-(dhMl hy Met- 

 calfs and ("ullins' melhod,' <»(' desiioN ini; advance infectious and 

 establishing an "ininnine /.one?" This is a te<-huieal (question of 

 fundanienlal inijioi-lance. It is a (jueslictn to \ut answered hy ex- 

 ]»eii niycoh)<j;isls and jdani pal h()h)uists. 1 have observed that 

 I he h-adini; advocates <d' the ineihod a\<»id. as far as ]»ossihh% dis- 

 cussion of its probable efl'ecl iveness. in I'arnieis" Ilnlletin 4U7, 

 (he (pU'stion is dis[»osed of i»y inserting into tin.' letter of trans- 

 mil lal the followinji senleiici*: "The ex[)erluiental (lata upon 

 Nvhich ihe recoininendal ions contained in this publication are 

 ltase(| w ill he pnliiislied in full in a forthcouiiug bulletin cd" tiie 

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

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

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

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

 D. C, conclude with the following stiitement : ''It is therefore 

 believed that this uiethod of attack will prove equally i)racticable 

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

 nltimately in the conti-oj of the I)ark disease." Up to the present 

 time the j»romise(| b!illetiii has not aj)i»eare(l and we are still in 

 the dark as to the nature of the ''experimeutal data." I had 

 hoped that it might be ])resented at this meeting. In justice to 

 the public it shouhl have been ])ublish(Ml before I5ulletin 4<»7. 

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

 l»e c(»ntt'olled. .\]»]>areiit ly, the s<de foundation for the optimis- 

 tic statements made by Metcalf and (Ndliiis in riulletiu 4(*m is 

 the result of the Held test" which they made at ^^'ashillgto^l aud 

 T hold that no delinite c(ni( Insions 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, ami ex]terimenters are 

 agTe(Ml that experiments without checks have little value. This 

 is one of the lirst ininciples of ex])erimentation. AVeather con- 

 ditions may have Iteen unfavoralile foi- the spreail of the disease. 



