APPLE BLIGHT IN REVIEW. 211 



portions, cutting several inches below the affected parts, being care- 

 ful not to spread the disease by infection from the knife; that in- 

 fection takes place chiefly through the blossom and at the tips of 

 young or rapidly growing shoots ; that in all other cases breaking 

 of the surface is necessary to infection ; that highly cultivated and 

 heavily manured orchards are more susceptible to the disease than 

 those making a slower growth, and that insects are the chief agents 

 in distributing the disease. 



There is an abundance of literature oi"k the subject, but the sub- 

 stance of Burrill's work will be found in Illinois Hort. Report for 

 1879; Arthur's Report of N. Y. Ag. Exp. Station for 1884, 1885 

 and 1886; Waite's in Year Book of Dept. of Agr. 1895 ; and report 

 American Pomological Society, 1901. 



Waite gives full directions in this Year Book of 1895 for the 

 cutting and removing of blighted portions, and as the book may be 

 had for the asking I shall not give details here. 



Mr. Yahnke: I would like to ask Prof. Robertson a question, 

 and it is this : This blight usually makes its appearance after a heavy 

 fall of moisture when the weather turns warm. The atmosphere is 

 very heavily laden with moisture, which is the time when the condi- 

 tions for tree growth are the very highest. That is the time when 

 blight generally appears. Now, how is it that it appears at just 

 this season? I have found that trees which are heavily pruned in 

 a dormant condition are affected the most of all by blight. You 

 heard what Mr. Smith said about the Hibernal and others blighting. 

 He cut the tops very nearly off and then had them top-grafted. The 

 roots were very well developed, very strongly developed. They 

 pushed the sap from the roots to the top, the top had no leaves to 

 evaporate the abundant moisture, and the result was that the limbs 

 were smothered and choked and fermentation took place. This fer- 

 mentation of this sap which is being pumped from the roots to the 

 top is not yet explained, but at the same time Mr. Smith would have 

 found if he had root pruned his trees as much as he pruned the top 

 and then top-grafted he would have had the best results and the least 

 blight. I had a row of Duchess trees that had stood in sod for a 

 few years and then they did not make much growth, but as a gen- 

 eral thing if a tree does not have a chance to make growth it de- 

 velops a strong root system. I was not satisfied with their growth, 

 and as the trees were on high ground I put on a heavy coat of manure 

 in the winter time. In the spring came plenty of rain, and the re- 

 sult was that the blight took nearly all the trees. The root system 

 of those trees was very strongly developed, the atmosphere furnished 

 the moisture to produce this blight, the sap was forced from the roots 

 to the top, and the top of the tree was not sufficiently developed to 

 use it up. If a man has been sick and his system is weakened, if you 

 feed him strong beef tea and heavy and rich food he is going to die, 

 and that is just the condition those trees were in. 



Prof. Robertson : If you noticed it I gave a little sketch of this 



