10 



HOST RELATIONS. 



This disease must be viewed with some additional concern 

 since it is not confining its attacks to a single species. As a 

 disease of the chestnut it is much less virulent than the End- 

 othia blight but it occurs on the chestnut beyond the present 

 range of the chestnut bark disease. Various species of oaks are 

 affected and in some localities the disease has made such head- 

 way as to cause some alarm. In the short experience with this 

 disease up to date it has been found attacking the following 



species : 



American chestnut, .Castanea dentata (Marsh.) Borkh. 



Chestnut oak, Quercus Pf^inus L. 



Black oak, ^' velutina Lam. 



Red oak, ruha L. 



Scarlet oak,, coccinea Muench. 



White oak, " alha L. 



The disease appears to be more severe on the red and black 

 oaks, and also produces more pronounced cankers on these 

 species. The most typical development of the disease upon oaks 

 has been observed in fairly dense stands in which a single 

 species predominates. The disease is more obscure on the white 

 oak than on any other species of oaks. This is due to the very 

 rough character of the normal bark, which may render incon- 

 spicuous lesions of some extent. The Strumella cankers on the 

 chestnut (fig. 9) are rarely as conspicuous as those caused by 

 Endothia. In some Strumella infections in this species the lesion 

 may reach a considerable size without showing much discolora- 

 tion or depression of the bark. There is but rarely any indica- 

 tion of concentric zonation in lesions on this species, while it 

 may be recalled that this character is especially marked in the 

 oak species. Ii. old cankers in all species there is gejj^rally 

 more or less corrosion at the center, so as to leave a rough, open 

 wound. It seems probable that all species of oaks will be found 

 susceptible to this disease. 



