CARTER: ILLINOIS TREES: THEIR DISEASES 41 



eral successive years may become stunted. Two or three thorough 

 applications of a fungicide, either dodine or zineb (Table 1) at 

 10- to 14-day intervals, will help to prevent defoliation. The first 

 spray should be applied when the leaf buds are opening. Trees 

 severely defoliated for several successive years can be given plant 

 food to stimulate vigorous growth, as described in the section 

 "Feeding." Leaves from affected trees should be burned in au- 

 tumn to eliminate the main source of the fungus, which over- 

 winters in fallen leaves. 



Buckeye and horsechestnut trees planted in Illinois should, 

 whenever feasible, be varieties that have shown resistance to leaf 

 blotch. A list of these may be obtained from the Illinois Natural 

 History Survey. 



Scorch. — Foliage scorch occurs on buckeye and horsechest- 

 nut trees occasionally during July and August. It is most likely 

 to occur on trees growing under adverse conditions. Scorch is 

 described under "Types of Tree Diseases." Feeding and watering 

 may aid trees in overcoming the eifect of scorch. 



CATALPA 



Catalpa trees occasionally are affected by powdery mildew 

 and leaf spot. However, most damage to these trees is caused 

 by a vascular disease called Verticillium wilt. 



Verticillium Wilt. — This vascular disease of western catalpa 

 is caused by the fungus Verticillium albo-atrum. Affected trees 

 may have one to several branches wilt occasionally or for sev- 

 eral years in succession. Loss of many branches destroys the 

 ornamental value of a tree. Some trees affected with wilt may die 

 within 1 or 2 years; others may live for many years (Fig. 40). 

 The treatment for trees affected with Verticillium wilt is given 

 in the section on maple. 



CHERRY 



Wild cherry trees are affected occasionally by leaf diseases 

 and stem diseases. 



Rust. — The fungus Tranzschelia pnini-spinosae causes leaf 

 rust on chokeberry, wild black cherry, and wild red cherry. The 

 small, dark brown to black spots produced on leaves are relatively 

 inconspicuous. Rust causes insufficient foliage injury to require 

 spraying. 



Brown Rot. — This disease, caused by the fungus Monilinia 

 fructicola, produces a limited amount of blossom blight and twig 



