52 



NEBRASKA STATE HORTICULTURAL ^OCIETY. 



spring or early summer from the leaves of the preceding year's 

 growth. Later the disease spreads from the parts first affected 

 to the new grow^th. 



In like manner cedar rust has two stages of growth. One stage 

 occurs on the fohage, twigs, and fruits of the apple in summer, 

 w^here it appears at first as definite yellowish spots, very unlike 

 the rather indefinite brownish spots caused by scab. On sus- 

 ceptible varieties the spots increase in size as the season ad- 

 vances, often running together to form large patches. By mid- 

 summer the affected parts of twdgs and fruits and the lower 

 surfaces of leaves show short thread-like growths. On some less 

 susceptible varieties, however, the diseased spots remain small 

 and undeveloped throughout the summer. The fohage of apples 

 is generally much more seriously injured by the rust than the 

 fruit is. Apparently only the most susceptible varieiies suffer 

 from diseased twigs. Figs. 3, 4, and 5 give some ide& of how the 

 disease appears on the leaves, twigs, and fruits of apples. Tlie 

 other stage of the rust occurs, not on the apple, but on the 

 fohage and twigs of cedar trees, where it appears during fall and 

 winter as small, brown knots, commonly called "cedar apples" 



Fig. 3 Leaves of the Wealthy apple, showing cedar rust. 



