43 



Wood rots are common on the walnut and butternut but not so 

 common on the hickory. 



A leaf spot of rather common occurrence is prevalent on the liickory 

 but is rare on the other hosts. This is known as "leaf mildew" but 

 is not the "powdery" mildew mentioned above. The fungus causing it 

 is called Microstroma juglundis. The leaves show white powdery 

 patches on the under surface early in the summer and later, yellowish 

 spots are noticed on the upper surface. A witches broom effect on 

 the shagbark hickory is supposed to be due to this fungus. 



Filbert 



Two "blights" are prevalent on the filbert. One caused by a 

 bacterium, seems to be confined to the Pacific Northwest while the 

 other, a fungous blight, is at present confined to the region east of 

 the Rocky Mountains. 



By far the more serious of these blights is the latter. It has been 

 stated that this alone has kept the filbert indjiistry from becoming es- 

 tablished in the Eastern United States. The fungus, Cryptosporella 

 anoviala is prevalent on the wild' American hazelnut throughout its 

 range but is not virulent enough on this host to cause serious trouble. 

 However, when the filbert becomes diseased, it is quickly killed back 

 to the roots or to the main stem. It is certain that the filbert in- 

 d^istry will be a very unsatisfactory venture until satisfactory methods 

 of control are secured. I am informed by some growers that they 

 are able to keep this disease in check but it will take a number of 

 years to establish this beyond question. This disease is similar in 

 its life history to the chestnut blight in that it is caused by a group of 

 fungi known as the Ascoviycetes. It produces enormous numbers of 

 fruiting bodies, black or ash-grey in color, on the twigs and' larger 

 branches. The fungus girdles the branch causing a sunken con- 

 stricted area. 



It is probable that the control of this disease will be obtained by 

 rigid cutting out and burning all affected branches. Also all wild 

 hazel plants in tlie neighborhood of the plantings will have to be re- 

 moved. 



Another disease of filberts not known to occur in this country but 

 common in Italy is caused by a species of yeast (Nematospora coryli). 



