Pomaceous Fruits 51 



are more or less covered with a white or grayisli fungous 

 growth, in the later stages of which are found numerous very 

 small black fruiting bodies approximately 0.25 mm. in 

 diameter. This fungus, while of comparatively little sig- 

 nificance to old apple trees, causes much injury to nursery 

 stock, often becoming so serious as to prevent successful 

 budding. Mildew has been reported as especially serious in 

 California and other states west of the Rocky Mountains, 

 and is of some importance in all apple regions. In the Pajaro 

 Valley the fungous mycelium has been shown to hibernate 

 in the buds, resulting in early spring infection of shoots. 



Another species of mildew, P. oxyacanthce (DC.) De Bary, 

 shows the same general characters as the mildew described 

 above, but is of less economic importance. Three or four 

 lime-sulfur sprayings at intervals of about two weeks, 

 beginning when the buds commence to open, have given best 

 results. 



Crown-gall. See peach. 



Soft-rot, blue-mold rot {Penidllium expansum Lk.). — Per- 

 haps the most common apple rot is found upon stored apples 

 late in the year. The light, tan-colored rotted area is soft 

 and watery. The decay results in the complete loss of the 

 affected fruit, and, by contagion, in loss to the fruit mass. 



Upon cracks in the decayed surface, and eventually over 

 the whole rotten part, appear tufts of very short delicate 

 fungous threads, at first white, soon bluish-green, very like 

 the common blue-mold so familiar to the housewife upon 

 canned fruit, the seal of which has permitted air. to enter. 

 This blue substance upon the rotten apple consists of myriads 

 of the spores of the causal fungus. This fungus is compara- 

 tively unaggressive and cannot force its way into perfectly 

 healthy tissue; a bruise or rupture of the skin is necessary 

 to its invasion. The best preventive is care to avoid bruising. 



Root-rot^'' (various fungi). — Death^ of trees, without 

 apparent reason from evidence above ground, is frequently 

 due to disease and decay of the roots. While the earlier 

 symptoms may vary, in general they include an abnormally 



