EXPERIMENT STATION BULLETINS. 479 



rally rich in organic matter. The disease may appear upon the new growth, 

 upon fruit spurs, or at any openings upon the branches and trunk where 

 the bark has been cracked so as to permit the entrance of the germs. 

 They can also enter through the flowers, or through the soft succulent 

 tissues of the leaves or stems. The leaves upon the diseased portions 

 turn dark brown and dry up, but remain for a considerable time upon 

 the branches. The bark of the diseased portions also dries and becomes 

 nearly black in color. When the disease is at work in the tissue* the 

 bark cracks and a thick sap exudes. This has a distinct taste and odor 

 of fermentation and the disease itself is nothing more than a fermentation, 

 brought about in the sap by the action of the bacteria. The remedy for 

 pear blight is much the same as for "black knot," and, when any of 

 the leaves show the characteristic appearance of the blight, the branches 

 upon which they are should be cut off a foot or more below where any 

 signs of the disease can be seen, and immediately burned. By the prompt 

 removal of the diseased branches, the disease can generally be checked, 

 while, if this is not done, it may spread until all of the surrounding trees 

 are affected. 



Agricultural College, Mich.. March 10. 1898. 



