356 STATE BOARD OF AGRICULTURE. 



the bark or they may protrude in the form of knotted swellings. When the 

 bark sloughs off the margins of the canker often show the attempt of the tree 

 to heal the wound by the formation of a roll of new tissue. Several different 

 fungi have been found to be the cause of cankers of the apple tree. They are 

 mostly wound parasites. Experiment Station Bulletin No. 70, University of 

 Illinois, 1902, discusses the princinal fungi causing these cankers. (See also 

 Black-Rot.) 



Badly cankered limbs might better be entirely removed and burned than to 

 attempt to save them. Cankers may often be healed by scraping or cutting 

 away all diseased bark and wood and treating with sulphate of copper wash, 

 and later coating with tar or paint. Spraying the trees as for scab will tend to 

 prevent attacks from canker-producing fungi of the apple. 



SOOTY BLOTCH. 



This is of quite common appearance on the surface of apples which seem to 

 have small patches of soot dusted on them. It is known to be of fungous 

 origin and while not injurious, produces an unsightly effect. Among the varie- 

 ties most effected are mentioned Greening, Northern Spy and Baldwin. It also 

 attacks pears, especially Anjou and Lawrence. The Bordeaux spray successfully 

 checks this fungus. 



LEAF SPOT. 



(Phyllosticta Pirina Sacc. & P. Limitata Pk.) (See Pear.) 



POWDERY MILDEW. 



(Podosphaera oxyacanthae (D. C.) D. Dy.) 



This fungus lives on the surface of the leaves and sometimes causes trouble 

 especially to seeding apples in the nursery. Prevented by spraying with Bord- 

 eaux. 



BUST. 



(Gymnosporangium Spp; roestelia stage.) 



Rust effects the leaves causing yellowish spots in which are located the spore 

 bearing organs of the parasite. The spores, which are of an orange color, attack 

 the twigs of the red cedar, causing swellings, the so called cedar apples. An- 

 other spore form from these "cedar apples" infects the leaves of the apple 

 causing the orange rust. This disease is quite injurious in some of the east- 

 ern and southern states but is not prevalent in this state. Paddock also reports 

 a rust of the same nature on the quince in Colorado. Cutting the cedar trees 

 which may be adjacent to affected orchards will tend to prevent this fungus from 

 becoming troublesome. 



FRUIT SPOT. 



(Phyllacora pomigena (Schw.) Sacc.) 



Fruit spot is not an uncommon trouble, especially on Baldwin apples. It 

 appears in the form of small circular, slightly sunken spots of a brown color. 

 This brown discoloration usually extends only a little way into the flesh of the 

 fruit and possesses a bitter taste. For this reason it is often confounded with 

 the bitter rot fungus. The disease spots give rise to spore producing pustules 

 if the conditions are favorable. This disease has been greatly reduced by spray- 

 ing as for scab. 



