DISEASES OF CITRUS TREES ] 55 



the roots and transpiration or evaporation from the 

 leaves, by which the foliage is deprived of its moisture at 

 a greater rate than the loss is made good. As a result 

 the leaves curl and dry up, and soon drop off, at the 

 same time the tree shedding most of the young fruit 

 along with the foliage. Very often many twigs and 

 branches are killed in the same manner, and in graver 

 cases entire trees are severely mauled or killed outright. 

 These cases of sudden death are fortunately very rare. 

 They are known by the name of brontesis, but the term 

 is also applied indiscriminately to cases of death by 

 lightning and to cases of equally sudden death caused 

 by root-trouble, in which an apparently healthy tree 

 succumbs in a day or two, to an insidious attack of root- 

 fungus ( A rmillaria mellea) or of gummosis of the roots. 



Citrus trees are more liable to ''sunstroke" after a 

 prolonged drought, or if they have been suffering at all 

 from want of irrigation. It often happens that an orange- 

 grove which in the morning showed no trace of this 

 disease, is found to be severely affected in the afternoon, 

 with shrivelled twigs and dried up leaves, which give the 

 impression that the trees had been exposed to the hot 

 blast of a furnace. In less severe cases only the leaves 

 are killed, the twigs remaining green and forming new 

 foliage soon after irrigation. The bitter or sour orange, 

 the mandarin orange and the shaddock are less liable to 

 this disease than other Citrus trees, and it is very 

 exceptional to have a slight attack of this disease within 

 three or four days after irrigation, and no severe attack 

 ever takes place within the first week. 



3. CARPOPTOSIS. All Citrus trees set considerably 

 more fruit than they are able to bring to maturity. At 

 the end of May or in the first days of June, the small 

 fruit begins to drop off, and by the end of June a certain 

 amount of selection will have taken place ; but this 

 shedding of the young fruit continues until the first week 

 of August, after which time it is stopped completely. 



