41 



but little work has been done along this line for the special purpose 

 of securing resistance. 



Chestnut Leaf Spot: One of the most serious diseases of the 

 chestnut is a leaf spot caused by Marssonia ochroleuca. I have col- 

 lected this several times in southern Illinois. During damp seasons 

 it causes a decided, reduction in the leaf area. It will probably never 

 become serious enough to warrant spraying but no dtoubt it could be 

 controlled by this method. 



Striimella canker: A common canker of the oak is also prevalent 

 on the chestnut. It is caused by Strumella ,coryneoidia. It frequently 

 girdles the twigs and even large limbs and may prove to be serious. 

 It is probable that this can be controlled by cutting out the cankers 

 but the fact that the oaks are common hosts of this fungus makes it 

 doubtful if cutting out would be a practical method since reinfection 

 would constantly occur. 



The chestnut is subject to the usual wood and root rots and has 

 several other leaf spots of minor importance. 



It should be remembered that the chestnut is a close relative of 

 the oak and is consequently, subject to many of the same diseases. 



Walnut, H ichor y and Butternut Diseases 



I class tlie diseases of these three nut trees together since most 

 diseases are prevalent on all three hosts, 



A leaf spot caused by Gnoinonia leptostyla (Marssonia juglandis) 

 is the most serious and wide spread disease of these three hosts. It 

 is worse on butternut than on walnut but seems to be very erratic in 

 its behavior on hickory nut. I have seen it cause almost complete 

 defoliation on one hickory tree while neighboring trees seem to have 

 suffered very little. It is probable that this is a varietal difference in 

 susceptibility since hickories differ very markedly in their characters 

 when growing wild. This point should be taken into consideration 

 when selecting wild hickories for grafting. 



This leaf spot causes large, dark brown irregular spots on the leaf 

 and these are frequently so abundant that the entire leaf is killed. 

 Even when not killed defoliation frequently results. Last summer I 

 watched a seedling butternut tree which grew near my dining room 



