MARKET DISEASES OF FRUITS AND VEGETABLES 31 



SCLEROTIUM ROT 



(Sderotium rolfsii Sacc.) 



A rot seen occasionally on the market on citrus fruits from Florida, 

 Puerto Rico, and Cuba is caused by the soil-inhabiting fungus Sde- 

 rotium rolfsii. The decay on grapefruit and lemons is yellowish 

 green, slightly darker than normal, whereas on oranges it is dark 

 brown with slightly lighter margins. At room temperature the decay 

 spreads rapidly through the entire fruit and if the air is moist, exten- 

 sive white, fluffy mycelium forms on the surface. In and on this 

 mycelium many spherical sclerotia one-sixteenth inch or less in diam- 

 eter are found. They are yellow at first, changing to deep brown. 



Because the causal fungus is a soil inhabitant, fruits touching the 

 ground are usually the only ones affected. However, the decay may 

 spread from a decayed to a sound fruit during transit if the shipment 

 is moved without refrigeration. If the disease is prevalent in the 

 grove, fruits touching the ground should not be packed. 



(See 43.) 



SEPTORIA SPOT AND STAIN 

 (Probably Septoria citri Pass.) 



Spots or pits caused by a species of Septoria, probably S. citri, 

 sometimes occur on lemons, grapefruit, and Valencia oranges in Cali- 

 fornia. The pits seen on fruit on the tree are usually not over one- 

 twelfth of an inch in diameter and do not extend below the oil glands 

 (pi. 15, B). Later they may enlarge to deeper pits one-eighth to 

 three-eighths of an inch in diameter. The smaller pits are light tan 

 to buff-colored and are surrounded at first by a green area that even- 

 tually turns reddish to reddish brown. The larger pits may become 

 dark brown or even black. 



Occasionally the small pits occur in a pattern known as septoria 

 stain, which is somewhat suggestive of melanose tearstaining on 

 Florida citrus fruit (see p. 5). 



Septoria spot and stain is rarely seen on the market and usually is 

 of only minor importance in the grove. 



(See 43.) 



SPOTTING AND SCARRING 



Oranges arriving on the market show at times various kinds of spot- 

 ting, which are usually hard to relate to a definite cause. Most of the 

 spots are brown, some are purely superficial, others are more or less 

 sunken, and all are roughly circular in outline. Descriptions and 

 illustrations of such spots have been published at various times, as- 

 signing as the causes: Fumigation injury; tree freezing; fungus at- 

 tack; localized physiological break-down; hail injury (pis. 17, Z?, and 

 16, D) ; and wind and leaf scarring (pi. 17, C and D) . These are 

 all causal agencies, the results of which have been observed and 

 authenticated. 



Some of the spots are described and illustrated in this publication. 

 (See Fumigation Injury (p. 28), Pitting (p. 5), and Aging (p. 18).) 

 The difficulty, from the market point of view, is that in many instances 

 the history of the fruit is not known and cannot be obtained; so 

 definite diagnosis of the cause cannot be made. 



(See 43.) 



