GRAPES AND OTHER SMALL ERUITS 17 



When grapes are fumigated with sulphur dioxide, bleaching around 

 the cap stems or at cracks in the skin is sometimes observed within half 

 an hour after the gas is released in the storage room or car. There 

 may also be a uniform fading of the color within that time. Browning 

 or marked dulling of the color develops later, probably because of the 

 time required for oxidation to take place in the injured tissues. It is 

 usually noticeable within 24 hours after the grapes have been removed 

 from a cool car or a storage room. 



Injury produced^ by sodium bisulphite may not develop for about 

 24 hours, because time is required for sulphur dioxide to accumulate in 

 the containers to a concentration that will cause injury. The rate at 

 which this accumulation occurs depends on the tightness of the con- 

 tainer or the room, the velocity of air movement around the fruit, 

 and the quantity of sodium bisulphite used (20, 23, 24, 25, 48, 49). 



SULPHUR INJURY 



When grapes are dusted with sulphur to control powdery mildew, 

 severe hi jury to the skin sometimes results. This appears on the side 

 of the berry exposed to the sun as smooth brown areas, varying in size 

 from about one-sixteenth to more than one-half inch across. The 

 spots are superficial and do not seem to lead to decay. Most packing- 

 house managers try to keep them out of the table pack, because of their 

 effect on the appearance and consequently on the market value of the 

 fruit. They are of no significance in juice stock. 



Prevention of such injury probably depends mostly on sulphuring 

 when the temperature is below 110° F., since field tests have shown 

 that sulphuring when the temperature is higher than about 110° is 

 dangerous to both leaves and fruit. Even distribution of sulphur is 

 also recommended to prevent injury. 



SUN KISSED 



The condition known as sun kissed or sun kiss on grapes consists of 

 tan to sometimes dark-brown spots that vary in size from one-fourth 

 inch in diameter to areas that cover fully half the surface of the berry 

 (pi. 27, A). Under a hand lens these areas show a delicate streaking 

 lengthwise of the berry, in contrast to the lacy appearance of mildew 

 spots. They are largest and darkest on bunches most exposed to the 

 sun, that is, at the top of the vine or on the southwest side, yet they 

 can be found on any part of the vine where bunches are so located 

 that the sun's rays strike them. 



The condition seems to be due to injury by sunlight or sun heat, 

 or both, for it is frequently possible, in bunches at the top of the vine, 

 to find all stages from the mildest sun kiss to the most definitely marked 

 sunburn (pi. 7, B) (p. 11) and even berries that are shriveled and dead. 



Sun kiss, though most common on Malaga, is sometimes found on 

 Alexandria (Muscat), Ohanez, Emperor, and Olivette de Vendemain. 

 It apparently does not lead to decay during the ordinary transit period, 

 except where the browning is severe and the skin shrivels and cracks. 

 If present in shipments to a greater extent than about 3 or 4 percent 

 it is considered objectionable by many receivers on the market. 

 Possible reasons for this discrimination against it are that it is held to 

 be a serious blemish on the fruit, or that since it usually appears in 



