MAKKET DISEASES OF APPLES, PEARS, QUI^-CES 55 



Pear scab is most common and most destructive in the northern 

 parts of the United States east of the Mississippi River. It can be 

 controlled by the treatment recommended for apple scab (p. 41). 

 {67, 100, 10 J^, m, lJi9, 1^2, 231.) 



SCALD 



COMMON FORM 



A brown to black discoloration of the skin of Bartlett, Bosc, and 

 some other commercial varieties of pears is known as scald. The 

 disease is apparently much less common on the market than apple 

 scald, and certainly is less understood. Although there is no defi- 

 nite proof that it is caused in the same way as apple scald (p. 44), 

 certain investigations have shown that, like apple scald, it is worse 

 on immature than on mature fruit and is most likely to occur when 

 ventilation is poor. In early stages the disease is entirely super- 

 ficial, but it progresses rapidly into the flesh at moderate or high 

 temperatures. In late stages the skin becomes weakened and sloughs 

 off readily, so that the scald is very likely to be followed by blue-mold 

 rot and other decays. 



The taste and odor of affected fruit are characteristically disagree- 

 able and sickening and can be detected in advance of the appearance 

 of actual discoloration. The ordinary form of scald has been found 

 to develop on pears of the Bartlett variety in 30 to 35 days at 43° F., 

 in 70 to 80 days at 36°, and generally does not develop at all at 31° 

 during the ordinary storage period for this variety. On other com- 

 mercial varieties, when these are stored at 32°, scald does not usually 

 develop to any serious extent until near the end of their maximum 

 storage period. Oiled paper as used for apple scald has not con- 

 sistently given control of this common form on pears. 



ANJOU SCALD 



On Anjou pears scald causes a brown or dark discoloration (pi. 

 18, D) which detracts materially from the appearance of the fruit, 

 but it is not accompanied by sloughing of the skin nor by unpleas- 

 ant odors as in the common form described above. The eating 

 quality is not impaired. The condition occurs (1) on both washed 

 and unwashed fruit, (2) on precooled fruit and on fruit that has 

 not been precooled, and (3) on fruit held constantly at 32° F., as 

 well as on fruit held for various lengths of time at other temperatures. 



The disease may be controlled by wrapping in oiled paper, so that 

 in these respects* Anjou scald seems to be similar to apple scald. 

 (92, 94, 96, 96, 139, IJ^, 170,) 



SILICATE INJURY 



On certain varieties of pears, both in car-lot shipments just arrived 

 on the market and in cold-storage lots, a brown spotting is sometimes 

 observed that is different in some respects from that caused by rub- 

 bing or bruising. It is often found on fruits that have been in con- 

 tact with the corrugated paper lining the boxes, or with the excelsior- 

 filled pads used in pear boxes to prevent bruising of the fruit. 



