MARKET DISEASES OF FRUITS AND VEGETABLES 5 



found in. or on the edge of. the wounds from which the gum exudes. 

 They vary somewhat in size but are rarely more than three-eighths of 

 an inch in diameter. 



HEAT INJURY 



(See Oranges. Heat Injury, p. 29. and pi. 12. C.) 



MELANOSE 



(Phomopsis citri Fawc.. 4 which also causes stem-end rot) 



Melanose occurs in all citrus-growing regions of the United States 

 and is also found in many other parts of the world where Citrus is 

 grown. In the United States it is probably of greatest importance 

 in Florida and the other Gulf States. Leaves, young twigs, and 

 fruit of various plants belonging to the genus Citrus are affected. On 

 the fruit the disease can be recognized as small, brown, raised spots 

 produced by the causal fungus* attacking and killing a few epidermal 

 cells of the rind (pi. 2. A). In these spots the fungus usually dies 

 long before the fruit matures. In mo^t cases the individual spot- are 

 about the size of a pinhead. although they may coalesce to form 

 rather large scablike patches known as •'mud-cake*' melanose (pi. 

 2. B). Sometimes the spots appear in a kind of tearstaining, but 

 they can readily be distinguished from the blemish of this name, 

 caused by citrus rust mites, by their brown, glazed appearance and 

 by the fact that they are slightly elevated above the surface of the 

 surrounding healthy skin. Melanose tearstaining is much more com- 

 mon than that caused by citrus rust mites. Melanose can be dis- 

 tinguished from the pimple stage of exanthema (ammoniation) by 

 the facts that the pimples of melanose are dark brown surrounded by 

 gray and when examined under a hand lens they are seen to be 

 cracked away from the healthy skin around them (pi. 3, A) ; those of 

 exanthema are dark reddish brown and, if they are cracked at all, the 

 cracks appear across the top (pi. 3, B). 



Melanose does not spread in transit. It is of importance merely 

 as a blemish, and its chief effect is to cause the fruit to grade lower 

 than it would if melanose were not present. 



In the average season in Florida the disease is readily controlled 

 by one or two applications of standard 3-3-50 bordeaux mixture. 

 Cutting out dead wood is an aid to control. 



(See J. 43, 96, 98, 135. 142.) 



OIL SPOTTING (OLEOCELLOSIS) 



(See Lemons. Oil Spotting (Oleocellosis), p. 14. and pi. 11, A 

 and B.) 



PITTING 



Pitting of citrus fruits, as its name indicates, consists of abruptly 

 sunken spots in the rind. It is sometimes called pox. but the use of 

 this term is undesirable. The spots are not discolored at first, but 

 later they may become slightly pink on grapefruit and eventually 

 brown on both grapefruit and oranges (pi. 4. A). Pits on Pineapple 



4 The perfect stage, Diaporthe citri Wolf, has been reduced by Wehmeyer (IS*) to 

 synonymy with D. medusaea Nitschke. 



