52 MISC. PUBLICATION 16 8, U.S. DEPT. OF AGEICULTURE 



west, Bartlett, Bosc, Cornice, and Clapp Favorite have been found 

 most susceptible, and Anjou and Winter Nelis are rather resistant. 



Various names have been applied to the disease by different 

 authors; among these are internal breakdown, core rot, and brown 

 heart. As the various names imply, the disease is characterized by 

 a softening and browning of the tissues in the region of the core 

 (pi. IT, D). The disease may be closely confined to the core or may 

 extend to the surrounding portions of the flesh. Sometimes the 

 softening is most pronounced in a zone about halfway between the 

 center and the outside of the pear. In the incipient form of the 

 disease the affected tissues are soft and watery, and in any stage 

 they have a disagreeable, sickening odor. In late stages the color 

 becomes brownish or black, and in severe cases rapid breakdown 

 and browning of the entire fruit occurs. The internal condition is 

 often associated with a discoloration of the skin resembling scald. 



Core breakdown is classed as a market or storage disease of pears, 

 but the time of its occurrence depends largely upon the maturity 

 of the fruit at the time of picking. Experimental tests have shown 

 that it is only the fruit harvested after its best picking time that is 

 likelv to become seriously affected later in storage or on the market. 

 {88,^89, 90, 91, U2, 152, 170, 225.) 



FREEZING INJURY 



^Yhen pears of the Bartlett and Anjou varieties are exposed to 

 freezing temperatures for long periods they develop a condition 

 that is fairly definite and positive in its symptoms. In all cases 

 the affected specimens have, externally, a glassy, water-soaked ap- 

 pearance (pi. 18, B). When such fruits are cut the water-soaked 

 condition is seen to be confined to certain portions of the flesh. 

 Usually it is found just beneath the skin and involves several layers 

 of cells. It may also occur within the core area. The remaining 

 flesh is usually dry and pithy, and in cases of severe injury may be 

 badly cracked, so that there are numerous open spaces. This form 

 of the injury has not been seen in other varieties than Bartlett and 

 Anjou. 



Pears showing the symptoms just described often remain in an 

 unchanged state for several weeks. They seem to be rather resistant 

 to decay and do not undergo normal breakdown from overmaturity. 

 Affected fruits are inedible and have no commercial value. 



The injury has been found to develop in 4 to 6 weeks in pears 

 held at temperatures slightly below their freezing point (23° and 

 27° F.). {93.) 



GRAY-MOLD ROT 



{Botrytis sp.) 



Gray-mold rot (pi. 13, A) is one of the most serious storage 

 diseases of pears. The term gray mold is descriptive of the gray 

 mycelium that appears on the fruit in the late stages of decay. 

 The disease is also known as cluster rot, a particularly appropriate 

 name, since a large number of affected fruits are frequently found 

 at one location in the package. The fungus mycelium grows from 



