42 



ILLINOIS NATURAL HISTORY SURVEY CIRCULAR 46 



dieback on wild black cherry. In blossom blight, the flowers turn 

 brown prematurely and wither or appear soft and rotting. Twig 

 dieback appears as drying and death of young twig tips. Cutting 

 out affected branches as soon as they are found will usually give 

 satisfactory control. 



Twig Canker. — The fungus Valsa leucostoma attacks weak- 

 ened cherry trees. It produces cankers and may kill inner shaded 

 branches and branches weakened by injuries. Cutting out af- 

 fected branches and stimulating vigorous gro\\i;h of the trees 

 by feeding and watering them should overcome this disease. 



Fig. 40. — Verticillium may cause foliage wilt on only a few or on all 

 branches of an affected tree. However, affected trees may recover and not 

 wilt again in succeeding years. This catalpa tree, which wilted in 1940, 

 recovered from the disease and continued to live for many years. 



