244 NEBRASKA STATE HORTICULTURAL SOCIETY 



/IVeatment: Since the disease is prevented by the prevention 

 of ap^le scab, spraying is about the onty remedy of economic 

 value. If the apples are healthy and free from injury no trouble 

 need be feared from pink rot. 



RUST. 



Cause: This disease is caused by a fungus {Gyinnosporangium 

 macropus) which hves during the summer on the apple twigs, 

 leaves or fruit, and in the winter on the red cedar. 



DescHption: The disease is the most noticeable on the leaves 

 of the apple tree in the spring or early summer. Orange 

 colored patches appear on the under surface of the apple leaves, 

 and often little projections occur directly over these on the 

 upper surface. The spores, formed at the spots on the lower 

 surface, germinate on leaves, or on the young twigs of the cedar 

 during the summer, and by fall they have formed the so-called 

 "cedar apple." The enlargement seen on the twigs of the red 

 cedar is not the fungus, but the abnormal growth of the red 

 cedar tissue caused by the presence of the fungus. This 

 growth continues throughout the winter and in the spring there 

 is an extrusion of a yellow gelatinous substance which contains 

 myriads of spores of the fungus. These find their way to the 

 apple tree and there begin their destructive work. It seems 

 necessary that the fungus shall have both the apple tree and 

 the red cedar in order to persist. The disease on the fruit had 

 not been observed in this State by the department of botany 

 until this winter. However, the fact that the fungus will attack 

 both fruit and twigs has been known for some time as shown by 

 B. T. Galloway, Report of the Chief of the Section of Vegetable 

 Pathology for 1888. He says in part: 



"Some species frequently attack the young fruit and twigs, 

 and in developing greatly distort them. This is particularly 

 true of Boestelia aurantiaca which infests several species of haw- 

 thorne, june-berry, apples and quinces." 



The Boestelia auraiitiaxM is the Boestelia stage of the Gynnios- 

 porangiuvi macropus, the common rust of the apple. 



A knowledge of the appearance of the disease can best be 

 gained from the accompanying cuts. 



