FIELD STUDIES OF THE DISEASE. 55 



Similar conditions were noted and followed through their course of 

 development in numerous other cases. Each time it was made 

 reasonably certain by careful examination that there was no disease 

 of the middle leaves, and then all of the lower infected leaves and 

 spikes were removed, one by one, and the trees left standing. In 

 the course of a few weeks the outermost flower spikes and swords 

 which had been left in an apparently healthy green condition now 

 became discolored and wilted. These were removed and only green 

 ones left. This was repeated until finally in every case a typical rot 

 appeared in the central leaves and quickly penetrated to the heart, 

 thus killing the tree. In all, 21 trees were pruned through a series 

 of months, as described above, and in each case the disease finally 

 lodged in the central leaves. These experiments seem to furnish 

 good evidence as to the origin and course of the infection. Although 

 no inoculations have been made to prove it, yet in no other way can 

 the condition be interpreted than that the water-soaked spots at the 

 base of the leaves and the black wet^rot of the strainer is the pre- 

 cursor of the central bud-rot (PI. X, figs. 1 and 2). Microscopic 

 studies of the water-soaked spots, showing numerous bacteria, confirm 

 this idea. 



With this evidence, then, as to the course of the disease, the ques- 

 tion as to remedies or preventives can be studied with a more thorough 

 understanding of the conditions. 



EEMEDIE8. 



When it was found that the disease often first occurred at the 

 inner leaf bases and gradually passed to the central leaves it was 

 hoped that some application might be made to the crown that would 

 destroy the incipient infections. 



If the leaf-base spots and external strainer rot could be removed 

 before the rot had penetrated to the deeper tissues there seemed some 

 hope of success. The methods of accomplishing this have been 

 varied. To remove the diseased tissues at the base of the leaves the 

 writer resorted to pruning. As mentioned in previous paragraphs, 

 21 trees were treated in this way. It appeared impossible, however, 

 to remove all of the infection. The germs could pass through the 

 strainer, and they might have been present in the tissues without 

 showing any sign of rot. For that reason it was difficult to tell how 

 much to prune. Cutting off merely the diseased area did not seem 

 efficient. As many as 15 to 20 leaves could be removed — leaving 

 5 or 6 — without seriously injuring the tree. To carry this further 

 would so weaken the crown that the ffi'st strong wmd would blow it 

 over entirely. In this work, as carried out by the writer, the trees 



228 



