40 



ILLINOIS NATURAL HISTORY SURVEY CIRCULAR 46 



Canker diseases frequently can be overcome by the cutting 

 out of diseased parts, followed by the feeding and watering of 

 affected trees to stimulate vigorous growth. However, trees se- 

 verely affected and trees growing in unfavorable sites probably 

 will not respond favorably to treatment. 



BUCKEYE AND HORSECHESTNUT 



Buckeye trees and horsechestnut trees in Illinois are affected 

 almost every year by leaf blotch, but they are relatively free of 

 other diseases. Occasionally they are affected by scorch. 



Leaf Blotch. — This disease is caused by the fungus Guignar- 

 dia aesculi. It produces, on the affected leaflets, small to large, 

 irregular reddish-brown areas with narrow yellowish margins 

 (Fig. 39). The diseased areas of an affected leaflet may be con- 

 fined to the margins or to tissues between the veins, or they may 

 cover most of the leaflet, including midrib, veins, and tissues be- 

 tween the veins. In time, the whole leaflet may turn brown and 

 fall prematurely. Fruiting bodies of the fungus appear as black 

 specks on the diseased tissues. Trees severely defoliated for sev- 



Fig. 39. — Leaf blotch of horsechestnut and buckeye causes small to 

 large reddish-brown areas with narrow yellowish margins to form on in- 

 dividual leaflets. Extensive blotching of leaflets results in premature 

 defoliation in late summer. 



