416 MANUAL OF FRUIT DISEASES 



ARMILLARIA ROOT-ROT 



Caused by Armillaria mellea (Fries) Quel. 



Raspberries are seriously injured by the shoe-string fungus 

 in the Pacific Northwest. (See fuller account under Apple, 

 page 96.) 



BLUE-STEM 



Caused by Acrostolagmus caulophagus Lawrence 



This is a raspberry and blackberry disease peculiar to the 

 Pacific Northwest. It has been increasingly troublesome in 

 the Puget Sound region since 1904. All blackcap varieties of 

 raspberries are susceptible. It also affects red raspberries. 



Symptoms. 



In general, when raspberries are affected with blue-stem the 

 plants fail to mature the crop properly and they may die during 

 the summer. The canes usually are first to show signs of the 

 disease. The fruit begins to dry up and harden before maturity. 

 This change in the fruit is accompanied by a discoloration and 

 wilting of the leaves and a darkening of the canes. Symptoms 

 vary with the severity of the attack. 



The first discoloration of the shoots occurs a few inches 

 above the ground. A blue-black stripe extends from some point 

 a few inches above the ground upwards on the shoot. The 

 stripe may be narrow, or the whole side of the shoot may be 

 dark-blue. Very commonly shoots are discolored throughout 

 their circumference for three feet from the ground. This dis- 

 coloration may increase three to six inches in length each day 

 during the growing season. At the ends the dark-blue area is 

 fringed and fades into a reddish brown color. The margin is 

 quite distinct. As a result of this affectation some shoots may 

 die. Death occurs throughout the entire growing season, al- 



