MARKET DISEASES OF FRUITS AND VEGETABLES 15 



Field observations and experimental work indicate that oil spotting 

 is a form of bruising injury. It is particularly likely to occur on 

 green citrus fruit if it is handled while wet. The immediate cause 

 of the injury is oil that is liberated from the oil glands by mechanical 

 injury. Pressure incident to the picking and handling of green- 

 colored fruit is particularly likely to cause the green spots, and bruises 

 incident to packing degreened fruit cause yellow or brown spots, the 

 severity of the injury depending upon the quantity of oil released. 

 Field freezing may also liberate oil and cause spotting. Fruits with 

 raised, prominent oil vesicles are more likely to suffer from oil spot- 

 ting than those with less prominent ones. 



(See 39, 43, 75. 119.) 



PETECA 



Peteca resembles pitting, but the depressions are more gently 

 rounded at the edges (pi. 1. C). The collapse begins with the albedo, 

 and the outer layer of the rind sinks without at first losing its normal 

 color. The oil glands soon begin to darken, and in extreme cases the 

 whole surface layer may collapse and become discolored. 



Peteca may develop in storage, but its occurrence seems to be largely 

 determined by previous orchard and climatic conditions. It is most 

 common on fruit picked in cold, wet seasons. 



(See 24, m 



PITTING 



Lemons sometimes become pitted if held for prolonged periods in 

 low-temperature storage (32° to 40° F.). The depressed areas of the 

 rind may range from one-sixteenth to one-half inch in diameter. 

 They sometimes retain their normal color but more often become 

 light brown or dark brown approaching black. 



The disease is rare on lemons held at a temperature of 50° F. or 

 higher, but it is likely to become serious on those held at 40° or lower 

 for more than a few weeks. A comparison of these statements with 

 those made in this publication relative to the control of other lemon 

 diseases brings out an important fact; namely, that the temperature 

 commonly used for the storage of lemons. 55° to 58°, is really a com- 

 promise. Below that range there is danger of serious loss from physi- 

 ological diseases — membranous stain, pitting, and red blotch — where- 

 as at higher temperatures heavy loss from fungus diseases is almost 

 sure to result. Within the range chosen there is a balance between 

 the two groups of diseases that permits profitable commercial opera- 

 tions. 



(See also 80 and references under Grapefruit, Pitting, p. 5.) 



RED BLOTCH (ADUSTIOSIS) 



Red blotch, or adustiosis. is a superficial scaldlike browning of the 

 surface layers of the lemon rind (pi. l.B). At first it may be a light 

 cinnamon brown, but in later stages it may darken into a chestnut 

 brown. 



The disease is limited largely to fruit picked in cold, wet seasons 

 and appears to be aggravated by forced curing. It seldom develops 

 in transit or on the market, but it is sometimes found on fruit that 

 has been held at 36° or 40° F. 



(See ftj, 42, 43.) 



