118 [ DISEASES OF THE OLIVE TREE 



and sometimes also on the roots. A protuberance is 

 developed from the size of a pea to that of a walnut, 

 within which the woody tissues are soft, and are in a state 

 of rapid growth; sooner or later the bark splits irregu- 

 larly, the outer part of the woody tissues dies, while the 

 inner part continues to develop, producing often a large 

 jagged and cancerous wound. The disease is common 

 everywhere the olive tree is cultivated, but is always less 

 severe on budded or grafted trees, although it is known 

 that the tubercle often forms on the wound soon after 

 budding, killing the bud or preventing its development. 

 The disease is more prevalent in badly ventilated groves, 

 and in the summer following a winter with severe hail- 

 storms. Small wounds made by hail or by any other 

 mechanical injury are too often the starting point of 

 infection, where a tubercle will develop sooner or later. 

 Unfortunately, against this disease, as well as against 

 other cryptogamic disease, such as the "blotch" of the 

 foliage, etc. there is no remedy of practical utility, beyond 

 good cultivation and regular pruning. Certain fungi of 

 the genus Polyporus etc. sometimes attack the olive tree, 

 and the infection is checked by removing the decayed 

 wood washing the wound with a solution of sulphate of 

 copper (5 p. cent.), and when dry painting it over with 

 liquid tar. 



Tviblydiella oliveforum Sacc., and Macrodiplodia 

 oleaginea Sacc. are frequently found on dry twigs, but 

 may be only saprophytic. Macrophoma Oleae (D.C.) 

 Berl. et Vogl. is found on dead leaves but is of no patho- 

 logical importance. The huge irregular pileum of 

 Polyporus biennis (Bull.) Fr. has been found growing out 

 of the cankered trunk of old olive trees. 





