DISEASES OF SHADE AND FOREST TREES. 97 



ANTIIBACNOSES. 



These diseases are very common and attack many different 

 s]M-cies of plants. They are due to fungi and many of them 

 arc also found on stems and fruits. On the foliage they 

 niav cause spots or holes, or a withering very 



> J Sycamore. 



similar to that caused by irost. 



The most important of the anthraciioses on shade and 

 ornamental trees is that on the Sycamore, caused by the 

 fungus Gnomonia veneta* (Sacc. and Speg.) Kleb. In. the 

 ( arlier stages of the disease it follows the veins of the leaves, 

 from which it eventually spreads. It also attacks the young 

 shoots. In severe cases the leaves are entirely browned and 

 withered and have very much the appearance of those in- 

 jured by frost, for which the disease is frequently mistaken. 

 It often kills the young shoots and sometimes kills the seed- 

 lings and young trees. This fungus is also said to cause leaf 

 spots on several species of oak. 



Treatment. 



Dead branches should be pruned out and the rough, loose 

 bark which may retain the disease should be removed and 

 bumed. The trees should also be sprayed with copper sul- 

 phate or lime-sulphur during the resting period, then with 

 Bordeaux mixture soon after opening of the buds, again in 

 ten days and again ten days later. 



POWDERY MILDEWS. 



The powdery mildews are due to fungi and are well known 

 on many plants. These fungi, unlike the preceding, do not 



*One stage of this fungus has been described under the name Gloeosporium 

 ncrrifteyuuiri Fckl. by which it was long known and by which is was referred 

 to in the Fourth Annual Report of the Forest Park Reservation Commission 

 of New Jersey 1908. 



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