SHADE TREES. 



195 



Schw.) grows in the secretions of woolly aphis, causing a large spongy black mass 

 on the leaves. 



Hawthorne {Cratcvyus) . — The leaves of the English hawthorne are affected 

 often seriously with Entomosporium thumenii Cke., which produces spots. 



Ash {Fraxinus) . — The stems and leaves of the ash for the past few years have 

 been troubled v/ith a rust (^■Ecidiuni fraxini Schw.). The worst cases have been 



Fi<i. «7 



Lirnien leaf spot {Cerrosponi) . 



found in the vicinity of Cape Cod. The ash is also subject to a leaf spot (Septoria 

 leucostroma E. & E.) and mildews {PhijUactinia suffulta (Reb.) Sacc. and Phyl- 

 losticta viridis E. & K.). 



Locust (Robinia). — The locust is unusually susceptible to borers, and when 

 attacked by them often l)ecomes infected with various species of fungi. 



Linden (Tilia). — The leaves of the linden are sometimes .badly affected with 

 leaf spots, svich as Cercospnrn microsora Sacc, which may be largely controlled by 



Fig. 6S.- 



Linden tree in center sprayed twice witli Bordeaux mix- 

 ture; otliers unsprayed. 



si)raying. The linden in some locations suffers very badly from frost cracks. The 

 American basswood {Tilia aniericana) is subject to a leaf mildew (I'ltcinulu clin- 

 tonii Lev.) and to the leaf spot (Cercospora tilia Pk.). 



Elm {Ulmus). — The most common leaf spot found on the elm is Dothidella ulmi 

 (Duv.), which is characterized by numerous small black spots on the upper surface 

 of the leaves. Another leaf spot cau.sed by Phleospora ulmi Wallr. is characterized 

 by numerous small spots from which gelatinous masses exude in damp weather. 



