19 1 4 



BETTER FRUIT 



Page 13 



The Battle of Cider Mill Ridj 



(Courtesy of tlie SpokecmaD-Review) 



Some Factors in the Control of Pear Blight 



By P. J. OTiaia, Chief in Charge of Agr 



THE interesting subject of pear 

 blight and its control has been so 

 frequently discussed before the 

 meetings of the various horticultural 

 organizations of the Pacific Coast and 

 Pacific Northwest that I take it for 

 granted that practically every grower 

 of pome fruits fully understands the 

 nature of this disease, which should be 

 properly termed the Bacterial Blight of 

 Pome F'ruits. Besides attacking all 

 pome fruits in a more or less serious 

 manner, the bacterial organism of pear 

 blight also attacks, in a limited way, 

 various members of the stone-fruit 

 family. I take it for granted that the 

 fruitgrowers who have heard the sub- 

 ject of pear blight frequently dis- 

 cussed know of its early history and 

 native origin, namely, that it is a 

 strictly North American disease anil 

 was first noted on the highlands of the 

 Hudson, New York, by William Den- 

 ning in 1780. Until a few years ago the 

 disease was confined to the North 

 American continent, but it is now 



icullural Investigations, American Snicltin 



known in two or three parts of Europe, 

 having been noted as occurring there 

 by certain agricultural explorers of the 

 United States Department of Agricul- 

 ture. However, from all accounts of 

 its occurrences in Europe we are led 

 to believe that it has not as yet be- 

 come a serious menace to fruitgrowers. 

 With this introduction, we will pro- 

 ceed to discuss some of the important 

 factors in the control of a disease 

 which in many ways is more de- 

 structive than all the other diseases 

 which the fruitgrower must combat. 



Cause of Serious Infection. — In order 

 to have a serious i)ear-blight epidemic 

 the following conditions are neces- 

 sary: (1) The germ must be present: 

 (2) insect or other agencies for the 

 "sowing" or spread of the blight or- 

 ganism must he plentiful and active; 

 (.3) conditions for the best develop- 

 ment of the germ after it has been 

 "planted" must be favorable. Another 

 factor, and an important one, might he 

 added, and that is lack of adequate 



Utah 



and Refining Company, Salt Lake City, 



means for the eradication and control 

 of the disease. It is easily seen that 

 there can be no infection if the blight 

 germ is not present, and, furthermore, 

 there can be no epidemic even though 

 the blight germ be present providing 

 the other factors are wanting. Those 

 who have had experience with pear 

 blight know that it will attack all 

 species of the pome family, and that 

 any part of the tree may become in- 

 fected, — blossom, twig, limb, body, 

 crown, root or fruit. Such exi)ressions 

 as "blossom blight," "twig blight," 

 "bodv blight," "collar-rot phase," "root 

 blight," "I'ruit blight," "lire blight," etc., 

 are all in a measure misleading, as 

 fruitgrowers are often mistaken in 

 thinking that the.se terms indicate a 

 dilferent disease in each case. The 

 term "(ire blight" is not a good one, for 

 the reason that fire-scorched trees do 

 not resemble trees badly blighted by 

 the blight germ. Furthermore, serious 

 infection which may result in the death 

 of the tree may not show any indica- 



