L)epartmental Activities. 27 



Blemishes of Citrus Fruits. — These may be classified under four 

 heads : Insects, fungus, mechanical, and physiological blemishes. 



(1) The blemishes due to insects are : Thrips scars, tortrix worm 

 holes, scale insects such as red, yellow, purple, and the sooty mould 

 which follows and grows upon the excretion of the black, gray, and 

 brown scales, mealy bugs, red s])iders, silver mites, grasshoppers, 

 and katydids. 



(2) Fungus blemishes. — The fungi which produce injury to the 

 fruit are brown rot (Phythiacystis citropJUhora) , blue mould {Peni- 

 cillium italicum), green mould (Penicillium digitatum), grey mould 

 {Botrytis cinerea), sooty mould {Miliola camellia), cottony mould 

 (Sclerotinia lihertiana), wither tip {Colletotrichum rjloeosporioides) , 

 and black rot of the navel {Alternaria citri). 



(3) Mechanical blemishes. — Serious losses are due to the follow- 

 ing : Bruises, thorn stabs, cultivator scars, clipper cuts, stem punc- 

 tures, machine injuries, and fumigation scars. These can to a large 

 extent be prevented by carefully handling fruit and using correct 

 equipment. The following are also responsible for bruises or 

 blemishes, but to a much lesser degree : Hail scars, soil scars, and 

 wind falls. 



(4) Physiological blemishes are due to sunburn, frost, off-bloom, 

 mottled leaf, brown spot, and cracks and splits. Seventy-five per cent, 

 of the culls in the citrus industry are due to six causes, which follow 

 in order of their importance : Splits, bruises, thorn stabs, thrips 

 scars, sunburns, and worm holes. Brown rot has not been takeii into 

 consideration, since it does not develop until the fruit leaves the 

 packing house. 



There is no effective control for splits or worm holes, but the 

 other four main causes of blemishes may be overcome to a large 

 extent; bruises may be controlled by careful handling of fruit, while 

 thorn stabs are being controlled by thornless vai'ieties, careful 

 pruning, and windbreaks ; pruning will also control sunburn to a 

 large extent; a spray of lime sulphur water and black leaf extract 

 is used against thrips. 



Frosted Citrus Fruit. — In sorting of frosted from unfrosted 

 citrus fruit, the successful segregation is impracticable from the 

 external appearance of the fruit. The principles of the method 

 now successfully adopted depends on the difference of the specific 

 gravity of frosted and unfrosted fruit, the former being consider- 

 ably lighter. The specific gravity of a well-grown unfrosted orange 

 is approximately .82, whilst that of one frosted is considerably 

 less. Before this difference in specific gravity is at its maximum 

 the fruits should remain on the trees for from 6 to 8 weeks — after 

 the occurrence of the frosting — which means that for export pur- 

 poses segregation should not take place for at least two months 

 after the injury if the frosted fruits are to be separated with any 

 degree of certainty. This time must be allowed for the changes 

 in the fruit to take place. 



Various methods and devices to effect this separation have been 

 tried, but the "Frank Chase Water Separator" is the only one 

 retained as being efficient and not expensive. The machine is thus 



