330 



STATE HORTICULTURAL SOCIETY. 



Careful watch should be 

 kept at all times, and when- 

 ever a knot is seen, it should 

 be cut off and burned. An 

 old knot may contain millions 

 of spores, and if dropped on 

 the ground it will scatter its 

 spores the same as if still on 

 the tree. If the knots are cut 

 off the first spring, before 

 growth has started, no spores 

 will have been developed, but 

 by the next spring two crops 

 will have matured, and the 

 spores scattered, that may 

 destroy every tree in the 

 orchard. Especial attention 

 should then be paid to the 

 destruction of the knots while 

 still green and soft. If the 

 knot is on the trunk of the 

 tree it should be cut off, and 

 the wound painted over with 

 linseed oil. Another remedy 

 that is highly recommended 

 is tincture of iodine applied 

 in the same way. If the tree 

 is badly affected, it should be 

 cut down and burned. A law 

 was passed by the last legisla- 

 ture, placing black knot in 

 the same legal position as 



■ S 



peach yellows, and the same 



methods can be used in 



securing the destruction of 



affected trees. Many of the 



spores could undoubtedly be 



killed by applications of 



fungicides, but it would need o be frequently repeated in order to secure 



entire immunity. 



Fig. 6.— Black Knot. 



1. Section through deceased stem, showing mycelium. 



2. Spermagonia. 



3. Asci and spores. 



4. Perithecium with asci. 

 5 and 6. Kipe Ascospores. 



7 and 8. Ascospores germinating. After Farlow. 



