133 



8. Frenclimg or spotting of the leaves with white and green fre- 

 >quently occurs in the more advanced stages of the trouble, but can 

 hardly be considered a symptom. 



9. Slightly swollen, stained spots often occur on leaves of trees in a 

 medium stage of the disease. Any slight mechanical injury or injury- 

 due to the attacks of the six-spotted mite (red spider), which works in 

 definite spots, is liable to be followed by a swelling of the leaves at the 

 points injured, accompanied by the characteristic stains, thus forming 

 brown, swollen spots. These spots are evidently formed only in places 

 where the leaves are injured. 



10. The fruits of diseased trees early assume a pale, sickly green 

 <5olour, which is quite different from the dark-green colour of normal 

 fruits. Some fruits split and fall while in this condition, but by no 

 means as many as fall in the next stage of the disease. 



11. When the fruits reach a size of from 1 to inches in dimeter 

 they gradually change colour, turning light lemon yellow and commonly 

 showing a slight brown exudation in places on the rind. At this stage 

 many fruits fall ; this usually occurs after the appearance of the brown 

 fitains, but sometimes before. On trees slightly affected many of the 

 fruits fall early, while on trees badly affected it is seldona thet any 

 fruits remain on the tree until they reach full size. The fruits usually 

 .split before dropping. At first a slight crack appears around the eye 

 end or apex of the orange, accompanied by a slight gummy exudation. 

 Finally a large split opens across the fruit, exposing the segments and 

 -causing the orange to rot and fall. 



12. Both the fruits which fall early and those which come to full 

 maturity are usually more or less disfigured by irregular brown stains, 

 similar to those occurring on the twigs. These stains frequently cover 

 a large portion of the fruit, rendering it unsalable. 



13. Slight swellings are sometimes found on the rind, particularly in 

 the sour orange. These swellings are caused by gum pockets formed 

 within the tissue of the rind. Very frequently a formation of gum also 

 occurs ia the segments immediately around the axis, generally near the 

 seeds. 



14. The fruit of trees affected with die-back usually ripens consider- 

 ably earlier than that of adjoining healthy trees of the same variety. 

 As a rule, however, it is large, very coarse, thick skinned, and disfigured 

 with brown stains, and in consequence often unsalable. 



15. The roots of trees affected with the disease usually have a 

 healthy appearance, but in severe cases, on improper soils, they fre- 

 quently become ulcerated and die back for some distance, the dead 

 ends rotting away. Roots which have died back frequently have large 

 and somewhat swollen ends, from which later on a number of small 

 roots frequently arise. 



The order in which the symptoms appear and their severity vary 

 greatly, but generally are as follows : The first sign of the disease is the 

 unusually dark-green colour of the foliage, rank growth, and large, 

 thick-skinned fruit. These symptoms are soon followed by the staining 

 and dying back of a few twigs, and by brown stains formed on some 

 of the fruits. The fruits developed are very prone to split and drop 

 prematurely. In the first stage of the disease either the stained fruit 

 or the stained, dying twigs must be present to determine with car- 



