CITRUS DISEASES. 



t i 



trees in low or very sheltered places, indicating that it is dependent 

 iipon humid conditions. In no ease has an entire tree been killed, 

 attack ha.ving been limited to one or at most several branches onh'. 

 The disease very often begins at the l)ase of a liuil), or at a point 

 where several originate, probably due to the accumulation of mois- 

 ture at these points, permitting the germinating spores to gain an 

 entrance. Once established the spread of the fungus is quite rapid 

 along the limb. If very moist conditions prevail, the limb may ])e 

 speedily girdled, but more frequently one side only (that which is 

 most shaded) is attacked. 



The presence of the thin, bright pink, fruiting layer of the fun- 

 gus is striking, so much so that this disease could not be confused 



with any othei-. Tlie pink area with 

 its narrow white margin often reaches 

 an extent of several feet, advancing 

 with the rot of the bark produced b.v 

 the vegetative portion of the fungus, 

 and even at times growing out over 

 tlie sound bark in advance of the root. 

 Not oidy is there a soft rot of the 

 I)ai'k witli a characteristic odor, but 

 till' wood beneath is attacked as well, 

 ]vsulting in its drying out. and be- 

 coming discolored. Various insects, 

 particularly wood borers, soon ai)pear 

 in the wounds, as do also various sap- 

 rophytic and wood-rotting fungi. 



The fruiting layci-. at tii-st a bi-ight 

 salmon pink, fades with age to a dull 

 gray oi- dii-ty white'. It also eracks 

 into small irregiilai'ly. rectangular 

 pieces, giving the characteristic ap- 

 pearance which has resulted in its hav- 

 ing been sometimes called the "writ- 

 ing fungus," the fragments being 

 thought to resemble hieroglyphics 

 (Fetch). Reproduction is brought 

 about by spores developed in immense numbers on the pink areas 

 and spread by wind, insects, and rain. • Although acting in some 

 cases as a wound parasite, it is quite capable in the presence of some 

 moisture of penetrating otherwise uninjured bark. 



Fig. S. — Cortirium saJmouicolor. 

 Illustrating the fniitiiig layer 

 of the fungus causing ' ' pink 

 disease. ' ' Note the normal 

 twig on the uninjured side of 

 the l)7-anf'h. 



