256 



Bush-Fruits 



SPUR-BLIGHT OF RED RASPBERRIES (FlG. 36) 



Mycosphcerella rubina, Jacz. 



This disease appears in the form of brown or bluish-black spots 

 on the young canes of red raspberries, in late summer or early au- 

 tumn. The spots may be from one to 

 four inches long and may extend partially 

 or wholly around the cane. The bound- 

 aries are sharply defined but only the bark 

 is affected, the cane itself being uninjured. 

 The disease is common on red raspberries 

 and is also found on Purple-Cane varie- 

 ties, but not on black-caps. During winter 

 the spots change to a light gray color and 

 the boundaries become indistinct. In 

 spring they are thickly studded with small 

 black spore-cases, known as perithecia, but 

 the wood is still uncolored and the cane ap- 

 parently uninjured in growth. In this 

 respect it differs decidedly from the cane- 

 blight. 



Recent investigations at the Colorado 

 Station show that the disease may do con- 

 siderable damage by killing the buds and 

 thereby preventing the formation of 

 branches on the lower portion of the cane. 

 Hence the name spur-blight. It appears 

 highly probable that the disease may be 

 controlled by the use of bordeaux mixture, 

 Spur-blight of t he fi rst application being made when the 

 new canes are a few inches high, a second 

 one shortly before the blooming period and a third soon after the 

 fruit is harvested; but it is doubtful if the damage done is suffi- 

 cient to warrant the expense of spraying. 



This trouble was formerly thought to be due to a bacterial disease 

 and was figured as such in a previous edition of the present work. 



Fig. 



36. 



raspberry. 



