Orchard and fruit Garden 



FIRE BLIGHT 



BY PROF. F. C. HARRISON, O. A. C. , GUELPH, ONT. 



THAT species of blight which is some- 

 times called the " fire blight," fre- 

 quently destroys trees in the fullest appar- 

 ent vigor and health, in a few hours turn- 

 ing the leaves suddenly brown as if they had 

 passed through a hot flame and causing a 

 morbid matter to exude from the pores of 

 the bark, of a black ferruginous appearance. 

 This happens throughout the whole course 

 of the warm season; more frequently m 

 weather both hot and moist." So wrote 

 William Coxe in a book on the " Cultiva- 

 tion of Fruit Trees," published in 1817, 

 which is said to be the oldest American book 

 on fruit culture. 



Nearly forty years before this we have a 

 record of the disease mentioned in a letter 

 written by one, William Denning, who first 

 saw the disease in the highlands of the Hud- 

 son in 1770. He described the disease 

 fairly well and thought it was due to a borer 

 in the trunk of the tree. 



From 181 7 almost to the present time we 

 find in horticultural literature many theories 

 as to the cause of the blight. It would be 

 tedious to give an account of all the differ- 

 ent theories put forward by various writers 

 during this period. The most diverse views 

 were entertained as to the cause of the dis- 

 ease, and it was a constant topic for discus- 

 sion in the horticultural journals and socie- 

 ties. These discussions were so wearisome 

 and so barren of results that the Western 

 New York Society resolved that the subject 

 should not be discussed at their meetings 

 imless some one had something entirely new 

 concerning the disease to communicate. 



'Amongst the numerous theories put for- 

 ward to explain the cause of pear blight, we 

 may mention the following: 



1. Insects. 



2. Rays of the sun passing through va- 

 pors. 



3. Poor or deleterious soil. 



4. Violent changes of the temperature of 

 the air, or the moisture in the soil. 



5. Sudden changes from sod to high til- 

 lage resulting in surfeit or overplus of sap. 



6. The effects of age ; old varieties being 

 most subject to it. 



7. Autumn freezing of unripe wood, 

 which engendered a poison which destroyed 

 the shoots 'and branches in the following 

 season. 



8. Electricity, or atmospheric influence. 



9. Freezing of the sap, or freezing of the 

 bark. 



10. The heat of the sun, assisted by rain- 

 drops acting as lenses causing the scalding 

 of the sap and bursting of the cells. 



11. Fermentation of the sap. 



12. The absence of certain mineral mat- 

 ters in the soil. 



13. An epidemic transmitted from place 

 to place by the air. 



14. Fungi. 



Each of the above theories was sustained 

 by various writers, and it may be of interest 

 to note that Henry Ward Beecher was an 

 advocate of the theory that the cause of 

 blight was due to the autumn freezing of the 

 unripe wood. 



A. J. Downing, the distinguished author 

 of " Fruits and Fruit Trees of America," 



