42 PROTECTION' OF PLANTS, 1915-16 



FIRE BLIGHT 

 Prof. F. Letourneau, Oka Agricultural Institute 



Fire blight is the worst disease attacking fruit trees in the Province 

 of Ontario. In the Niagara district it causes an annual loss amounting 

 to several thousand dollars. It exists also in the Province of Quebec. In 

 our orchards at La Trappe it has killed some pear trees. It is on this 

 account I have chosen Fire Blight as the subject of this paper. 



What Fire Blight Is; Its Causes. 



Fire Blight, also called Twig Blight, Pear Blight, and Blight Canker, 

 is a bacterial disease, attacking and killing different kinds of fruit trees. 

 It is caused by a micro-organism called Bacillus amylovoriis. This micro- 

 organism finds a ready nourishment in the plant tissue of our most common 

 fruit trees. Plants or animals cannot always resist the attacks of para- 

 sites or outside organisms. They struggle for a while and sometimes recover, 

 but, frequently, if man does not protect them, they soon die. In the case 

 of Fire Blight, the leaves suddenly turn brown as if scorched by fire, thus 

 explaining the name of the disease. 



Origin and Distribution. 



Fire Blight is peculiar to North America, where it has been known 

 for a century. Today we find it not only all over the United States but also 

 in Ontario, Quebec and British Columbia. 



Fruit Trees Susceptible .to Attack by Fire Blight. 



The disease does more harm to pear trees than any other fruit trees. 

 It is for this reason that most authors call it Pear Blight. It appears that 

 certain varieties have more resistance than others. In particular, the 

 Kieffer and Seckel seem to be more immune than Flemish-Beauty, Duchess, 

 Bartlett and Clap's Favourite. However, Fire Blight attacks not 

 only pear trees, but also apple trees, especially during the early stage of 

 its existence. In British Columbia it is said that Spitzenberg is the apple 

 tree that suffers the most. Mcintosh Red, in the same province, seems to 

 be very resistant. 



Besides pear and apple trees. Fire Blight attacks quince and even 

 plum trees, hawthorn, and mountain ash. 



