78 



THE DESTRUCTIVE AGENTS OF FORESTS. 



practicable to carry on spraying operations. Another method of 

 control is to rake together and burn diseased leaves in the fall or 

 early spring. 



Leaf-spots are caused by a large number of minute fungi be- 

 longing to several genera. The fungi producing leaf -spots may 

 become troublesome here on such trees as silver maple, sugar 

 maple, red maple, chestnut, v^alnut, hickory, pawpaw, witch 

 hazel, and the buckeyes. A leaf -blight {Gleosporium nervise- 

 quum Sacc.) is commonly found on sycamores. A serious leaf- 

 blight of white pine occurs from New Hampshire to North Caro- 

 lina. The cause of this blight is not well understood but it is be- 

 lieved that fungi often found present are responsible in part. 



Leaf-spots and leaf-blights may be controlled in the man- 

 ner recommended for the control of rusts. 



Fungi That Injure Bark. 



The bark of trees is affected to some extent by nearly all the 

 wood-destroying fungi in their advanced fruiting stage. There 

 are, however, some fungous diseases which are distinctively bark- 

 destroyers. Among these are the slime-fluxes which work in the 

 inner bark of such trees as the white elm, the maples, the yellow 

 birch, and the flowering dogwood. The bark which is sometimes 

 killed by these diseases, in broad girdles extending around limbs 

 and trunks of trees, is affected by various forms of algae, bac- 

 teria, and fungi. Special attention should be called to a serious 

 bark disease which affects both chestnut and chinquapin trees. 

 The disease is caused by a fungus known as Diaporthe parasitica 

 Murr. It was first observed in the City of New York in 1904, at 

 which time it had already damaged a large number of trees. Dr. 

 W. A. Murrill, who first described the disease, estimates that it 

 has caused a financial loss in New York City and vicinity of "be- 

 tween five and ten million dollars." Over 16,000 chestnut trees 

 were killed in a single park on Long Island. So far the disease 

 has spread to Rhode Island and Massachusettes on the north, and 

 through New Jersey, Delaware, Pennsylvania, and Maryland to 

 Virginia on the south. The most recent reports of the occurrence 

 of this disease are from Boston, Massachusetts; Saratoga and 

 Cooperstown, New York; Derry, Greensburg, and Kittanning 



