152 Bulletin 272. 



are Kiefer, Seckle and Anjou. We believe most growers will agree 

 with this, although it is not rare to see Kiefers, for example, severely- 

 attacked by the disease. The same variety will suffer more in one 

 section or in one season than in another. Among the apples, the crab 

 and its allies are most severely attacked; of the other varieties, no 

 strikingly constant difference in susceptibility has been recorded. The 

 whole question of varietal susceptibility to this disease is, we believe, 

 so bound up with other factors, such as source of infection, abundance of 

 disseminating agents (insects), and the like, that only a series of care- 

 fully conducted infection experiments on a large number of varieties 

 at the same time and under the same conditions can give correct con- 

 clusions. Suffice it to say that all varieties of apples and pears are known 

 to suffer at times to a greater or less extent from this disease. 



Manuring, cultivation, etc., as related to severity. It is the common 

 belief of growers, horticulturists and pathologists that, in general, 

 cultivation, the application of nitrogenous manures, or anything that 

 tends to induce rapid and succulent growth favors the serious develop- 

 ment of Blight, at least in pear trees. So far as the writers are able 

 to discover, this general opinion is based alone on observation. No 

 carefull}' conducted experiments appear to have been made to determine 

 anything definite on this phase of the question. After having seen old 

 pear trees that had stood in the sod all their lives, with no food other 

 than that which they could wrest from the sodded soil of a stony hill- 

 side, blight to the ground in a single season, the writers reserve judgment 

 until proof is forthcoming. In the meantime we advise growers to 

 cultivate their pear orchards if they desire crops of fruit and depend on 

 tried methods of controlling the disease, as indicated in the latter part 

 of this bulletin. In this view we are supported by Prof. U. P. Hedrick 

 of the State Experiment Station at Geneva, N. Y., who after several 

 years of careful observation on this point is of the opinion that cultiva- 

 tion and manuring do not play the important part in Blight epidemics 

 commonly attributed to them. 



THE DISEASE 



Names. Blight, Pear Blight, Fire Blight, Blossom Blight, Twig 

 Blight, Fruit Blight, Sun Scald, Canker and Blight Canker are among 

 the names frequently given to this malady on different kinds of trees 

 or different parts affected. The term " Fire Blight " is perhaps the 

 most appropriate since it applies equally well to the characteristic 

 symptoms of the disease on any of the trees on which it is now known 



