38 MANUAL OF TREE DISEASES 



liquid or dust form. Gathering and burning the fallen leaves 

 will reduce the amount of primary infection in the spring. 

 During the summer, when it is desired to prevent the further 

 development of these fungi, flowers of sulfur or preferably 

 finely ground sulfur-flour may be dusted on the affected leaves. 

 For large trees, blowers must be used which wiU produce a fog 

 of the sulfur-dust that will settle all over the foliage. Lime- 

 sulfur solution (1-50) with the addition of three pounds of 

 iron-sulfate to each fifty gallons of the mixture is also effective. 

 'Bordeaux mixture and other copper mixtures are not advised. 

 If possible, the application of sulfur-dust should be made in the 

 early morning while the trees are still damp, and preferably at a 

 time when weather conditions are to continue warm and dry. 

 The fungicidal value of sulfur is much greater under such 

 conditions. For fuller directions on spraying and dusting, see 

 page 357. 



Refbhencb 



Salmon, E. S. A monograph of the Erysiphaceaa. Mem. Torrey 

 Bot. Club 9 : 1-292, pis. 1-9. 1900. (BibUography given.) 



Leaf-Cast of Conifers 



Caused by fungi of the genera Lophodermium, Hypoderma and 

 HypodermeUa 



Several similar diseases of pine, larch, fir, spruce and juniper 

 are known under the general name of leaf-cast. Other names, 

 such as leaf-browning, leaf-reddening and cracking-scurf, have 

 been applied to these diseases. In Europe the leaf-cast diseases 

 of conifers have often assumed the nature of epiphytotics and 

 serious damage is common in nurseries and in the forest. Before 

 the cause of the leaf-cast diseases was known, they were con- 

 fused with all types of leaf -browning of conifers. The Scotch 

 pine is the most severely injured of the various conifers affected 

 in Europe. In the United States the leaf-cast diseases have 



