CITRUS CULTURE 1ST PORTO RICO 



31 



HARVESTING AND HANDLING 



The work of harvesting and handling the fruit in Porto Rico 

 is better systematized than any other part of the industry. The fruit 

 is picked by means of clippers, and generally it is carefully handled. 

 It is transported from the field to the packing house in field crates, of 

 which several suitable kinds are to be found on the market. Most of 

 the packing houses are equipped with standard machinery, and use 

 standard methods throughout. Packing-house problems awaitino- 

 solution include coloring, cleaning and grading, and decay. 



Coloring the fruit artificially is necessary early in the season be- 

 cause citrus fruit does not change color from green to yellow as soon 

 as it reaches the stage of maturity at which it is edible. Coloring is 

 induced by keeping the freshly picked fruit in an air-tight compart- 

 ment for varying lengths of time, at varying temperatures, and with 

 varying amounts of ethylene. Variations in the above-mentioned 

 factors are clue to variations in the coloring quality of the fruit. 

 These have been studied by the writer for many years, and some of 

 them may profitably be discussed at this time. 



One set of variations is due to differences in dormancy of the rind 

 tissue. Starvation of the tree or prolonged drought causes the rind 

 of immature fruit to turn yellow, after which irrigation and fertili- 

 zation with nitrogen may cause it to turn green again. Fruit which 

 has turned partly yellow because of tree dormancy is readily colored 

 by means of ethylene even when very immature ; whereas fruit which 

 has again turned green because of renewed growth is very difficult to 

 color by any method. This helps to prove that the trees should not 

 be fertilized and cultivated later than about June 1 if they are to 

 produce marketable fruit in September. Of course 'adverse "weather 

 conditions may- upset all calculations, and some trees may remain in 

 a vigorous condition long after others have become dormant. The 

 desirable state of dormancy or colorability of the rind can be deter- 

 mined by measuring the catalase content. This has not as yet been 

 correlated with the amount of gas needed nor with other coloring- 

 room conditions. 



Rind blemishes and covering of various kinds cause differences in 

 colorability. For example, the rind of fruit which is attacked by 

 scab can not readily be colored artificially, probably because of a 

 change in the surface tissue which practically inhibits respiration. 

 The effect of the purple scale (Lepidosaphes beckii) is similar to 

 that of scab. Fruit which is infested with scale may color perfectly 

 when left to mature on the tree. However, when the fruit is picked 

 green and colored artificially the spots underneath and immediately 

 surrounding the live scale will be found to remain green and the 

 green spots to contain more catalase than the surrounding tissue. 

 The rufus scale (Selanaspidus articulatus) produces the very 

 opposite effect. The spots covered by it are light yellow long before 

 the fruit reaches maturity, and the colorability of the intermediate 

 rind is not affected. Fruit that has been sprayed with oil emulsions 

 shortly before it is picked is not readily colored by ethylene, prob- 

 ably because of the oily covering which inhibits respiration. The 

 same effect is produced by any covering which leaves a thin film 



