THE ASCOSPORE AND OTHER FUNGI 



243 



Those that fall upon green and tender bark are likely to 

 germinate and start the disease again. 



As cold weather approaches, the tissues of the outer bark 

 become much harder, with many little cavities inside. The 

 fungus produces within these cavities 

 spores that germinate the following 

 spring and start the disease anew. 



The Black Knot affects most varie- 

 ties of plum and cherry trees, both 

 wild and cultivated, and the spores 

 are easily carried from one sort of 

 tree to. another. Consequently, it is 

 important that in any locality all 

 traces of the fungus should be ex- 

 terminated. The cutting down of 

 worthless trees and the pruning away 

 of diseased branches are the first 

 steps in the control of Black Knot. 



The cutting out of the injury as 

 soon as it appears and spraying with fungicides will also 

 help to control it. 



Black Knot on Wild 



Cherry ; winter 



condition 



Peach Leaf Curl 



Peach Leaf Curl is the name applied to a malady 

 that often affects the twigs and leaves of peach trees. It 

 causes the leaves to swell and curl soon after they expand 

 in spring, giving them an abnormal appearance that is at 

 once recognized as due to a diseased condition. The threads 

 of the fungus penetrate between the cells, growing rapidly 

 and causing a swelling of the tissues. The injured leaves 

 fall off in the spring or early summer. The twigs affected 

 also become swollen and distorted. Sometimes the disease 

 is confined to a branch or two, but frequently it involves 



