ORANGE AND LEMON ROT. 249 



ORANGE AND LEMON ROT.* 



The cause of the rot of oranges and lemons is the growth, 

 through their substances, of a mold fungus known scientifically 

 under the name of Penicillunn dujitaium. The growth of this 

 plant within the fruit causes a softening and breaking down of 

 the tissue, a very characteristic change in the flavor of the 

 juice, and, sooner or later, a very pronounced discoloration of 

 the afiected part. The fungus belongs to a genus consisting of 

 a number of well-known species, all having much the same 

 manner uf growth and producing decays on various substances. 

 The name "blue mold" applies to the whole group. The best 

 known species is Fcnicillium crustaccum, or, as it is more com- 

 monly called, PeniciUiuvi glaucum. This species is one of the 

 common forms of rot-producing fungi that attack deciduous 

 fruits, but it is probably even better known from its attack 

 upon all manner of substances in the household, such as cooked 

 foods, clothing, etc. While Pcnicillium crustaceurn is thus 

 found in a great \ ariety of situations, it appears iha,t Penicillium 

 digitatum attacks only citrus fruits, confining itself wholly to 

 these. 



The rot of citrus fruit is not usually a disease of the orchard. 

 In lemons the infection occurs almost entirely in the curing- 

 house; and in oranges, as a rule, after they are packed and on 

 their way to the East. Navel oranges, however, very often 

 come into the packing-house badly infected by the disease. 

 The trouble begins at the navel end, and may be scarcely 

 visible from without; though commonly a sliglit split, or per- 

 haps a little gum, will indicate the point of entrance of the 

 fungus. In this case the trouble clearly arose in the field, and 

 even began before the fruit Avas ripe. It is usually confined to 

 a limited part of the fruit, perhaps the upper end of one or two 

 sections, and very often produces spores within the cavity 

 caused by the shrinkage of the affected tissue, so that the 

 affected part n:;ay be badly discolored. In any citrus fruit a 



*tJv C. W. AV.jodwortl], in University of Calif.irniu Kulletin Nn. 139. 



