INSECT AND FUNGOUS ENEMIES OF THE APPLE. 83 
, 
cent to cedar trees may become so badly affected that the trees appear 
yellowish, even from a distance. In such cases the function of the 
leaves is so interfered with that the fruit, the buds for the following 
year, and the tree itself are not properly nourished. ‘This results in 
small, immature, poorly colored fruit, as well as weak buds and a 
weakened condition of the tree. Badly affected leaves usually drop 
prematurely. 
Cedar rust appears on the fruit of the apple as bright yellow spots 
about one-half inch in diameter or sometimes larger. Both the black 
dots and the cluster cups occur on the spots, the latter usually 
forming one or more rings near the margin. (See fig. 18.) The 
spots may occur at 
any point on the 
fruit, but they are 
most frequently 
found near the blos- 
somend. In severe 
cases the affected 
fruit may become 
deformed or atro- 
phied, but as a rule 
there is no disfig- 
uration other than 
the presence of the 
yellow spot. The 
market value of af- 
fected fruit is natu- 
rally reduced, much 
of it being dis- 
carded as culls. The disease on the fruit is not so important as that 
on the foliage, the greater damage being caused by the latter. 
Fig. 18.—Cedar rust disease on the apple. 
LIFE HISTORY OF THE CEDAR-RUST FUNGUS. 
There are several different species of rust fungi which pass a part 
of their existence on the red cedar and are obliged to spend the 
remainder upon the apple or some other pomaceous plant. Perhaps 
the most common of these is the one known as Gymnosporangium 
juniperi-virginiane Schw. The spores produced in cluster cups which 
occur on the diseased leaves and fruit of the apple are carried by the 
wind to the red cedar trees, infecting the twigs of the latter and thus 
producing the well-known “ cedar apples.” (See fig. 19.) These are 
reddish-brown, globular swellings ranging in size from one-fourth 
to 1 inch or more in diameter when mature. The fungus thus estab- 
lished on the cedar passes the winter and develops during the follow- 
492 
