CARTER: ILLINOIS TREES: THEIR DISEASES 



43 



CHESTNUT 



Of the leaf and stem diseases that occur on chestnut trees 

 in Illinois, chestnut blight is the most destructive. 



Chestnut Bliiiht. — This disease, also called Endothia canker, 

 is caused by the fungus Endothia pa)-asitica. One of the most 

 destructive tree diseases in North America, it has practically 

 eliminated the American chestnut from the eastern United 

 States. Development of chestnut blight is indicated by yellowing 

 and browning of leaves on affected twigs and branches. Dead 

 leaves and burs cling to diseased branches and are conspicuous 

 during the dormant period. Young cankers develop as yellowish- 

 brown, oval to irregular areas on smooth-barked, vigorous-grow- 

 ing young stems (Fig. 41). They appear as brownish, discolored 



Fig. 41 (top). — Cankers produced by chestnut blight appear as yellow- 

 ish-brown, oval to elongate areas on smooth-barked stems of American 

 chestnut. The canker in this picture is swollen, and cracks have formed in 

 the diseased bark. The small bumps or raised spots in the bark are fruiting 

 bodies of the chestnut blight fungus. 



Fig. 42 (bottom). — Cankers on Chinese chestnut most often appear 

 on young trees growing in sites that have high humidity and poor circu- 

 lation of air. These conditions frequently prevail in nursery plantings. 



