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on the cedar, are a familiar sight. (Fig. 10.) These galls are 

 dull reddish brown in color and vary from the size of a pea 

 up to nearly 2 inches in diameter. On the surface are scat- 

 tered small circular depressions. In the spring, brown horns 

 about an inch long protrude from these depressions, and in 

 rainy weather these horns become gelatinous and bright orange' 

 in color. At such times, when there are many "cedar apples" 

 on a cedar tree, the tree appears at a distance to be in blossom. 

 It is from these gelatinous horns that the spores of the causal 

 fungus spread in the spring to the apple. On infected apple 

 leaves small yellow spots , develop, and these soon become 

 larger and orange-colored. Clustered in these spots, on the 

 lower side of the leaf, are minute cuplike bodies in which the 

 spores of the fungus are formed. These give the name "clus- 

 ter-cup" stage to the summer form of apple rust. (Fig. 11.) 

 The fruit may be similarly affected, usually at the calyx end. 

 From this stage the spores are blown to the cedars, which thus 

 become infected to produce the "cedar apple" stage. 



Apple rust cannot be spread from one apple tree to another, 

 nor from cedar to cedar; hence, if either host is absent from 

 a region, the fungus cannot complete its life cycle and therefore 

 becomes exterminated in that area. 



The obvious line of attack on apple rust in the orchard is 

 therefore through destruction of all the cedars within infection 

 distance of the orchard. In regions where the disease is most 

 serious it has been determined that the cleaning up of cedars 

 within a radius of 1 mile of the orchard will reduce infection 

 to a very small amount and that 2 miles' clearance will prac- 

 tically free the orchard of rust. In Massachusetts, where in- 

 fection is seldom very heavy, a clear radius of half a mile 

 should be sufficient to keep the orchard relatively free of rust. 



It is not, of course, always possible for one man to control 

 the land over such a wide area, but co-operation among neigh- 

 bors will accomplish much and is worthy of a trial. In some 

 States there are laws which require the destruction of all cedars 

 which menace an orchard. 



