FRUITS 253 



become crumpled and mottled with yellow, the twigs 

 exude drops of gum, and these symptoms are fol- 

 lowed by the more or less extensive dying back of 

 the branches. In the case of severe attacks the tree 

 may ultimately die, but more often it lingers on in an 

 unthrifty and unprofitable condition. Such trees may 

 ultimately be restored to health by pruning out the 

 diseased wood and giving great care to fertilizing and 

 cultivation in order to carefully avoid the exciting 

 cause. When an orchard is seen to be threatened with 

 "die back," cultivation should be stopped at once so 

 that the grass may grow and thus take up some of the 

 excess of nitrogen, and some benefit may be derived 

 from additional applications of potash and acid phos- 

 phate, which would tend to restore a proper balance 

 in the food supply. 



Foot rot, or mat di gomma^ as it is called by the 

 Italians on account of the flow of gum which accom- 

 panies it, is an obscure disease, the cause of which 

 has not been clearly ascertained. It causes the dy- 

 ing of more or less extensive areas of the bark usu- 

 ally at or near the crown of the tree. As a rule it is 

 worse on wet, heavy lands. The sweet orange, when 

 on its own roots, is particularly susceptible to this 

 disease, while the sour orange is quite resistant. 

 The disease often girdles and kills the trees, but it is 

 by no means always fatal, and old trees are often 

 seen still fairly thrifty and bearing heavy crops while 

 their bases are badly scarred by old attacks of this 

 disease. Serious losses can usually be avoided by 

 giving good drainage and especially by planting 

 trees budded on sour orange roots. 



