58 



ILLINOIS NATURAL HISTORY SURVEY CIRCULAR 46 



each one-fourth to one-half inch long and about one-eighth inch 

 in diameter. They swell during periods of rainy weather in April 

 and May and elongate until they are approximately 2 inches in 

 length (Fig. 54). In dry periods following rainy weather, they 

 contract and appear as thin, wrinkled threads (Fig. 55). In late 

 May or June, they become dry and brittle, and finally drop off the 

 galls. The galls dry, shrivel, and turn black. The shriveled and 

 dried galls do not produce spore-horns in succeeding years, al- 

 though they may remain attached to the juniper. 



On apple and crab apple, cedar-apple rust infects leaves and 

 fruit ; however, it is not especially noticeable on fruit of crab 

 apple. The rust appears on leaves in May, first as very small, pale 

 yellow spots visible only on the upper surfaces. These spots be- 

 come orange and raised as they enlarge. By the time they are 

 about one-eighth inch in diameter, orange-colored drops of exu- 

 date appear near their centers. Later, because of the yellowish 



Fig. 54. — During rainy weather in April and May, each mature gall of 

 the cedar-apple rust is covered with numerous gelatinous, finger-like, orange- 

 colored spore-horns, which protrude from the gall. 



