CITRUS DISEASES. 99 



No damage is caused, except through the cutting off of light from 

 the food-manufacturing tissues of the tree by the lihick fungus layers 

 growing superficially over fruit, leaves, and twigs. A variety of 

 spore forms are produced, but whether they are of one species or sev- 

 <eral has not been definitely worked out. 



Sooty mold can be eliminated by killing the scale or other in- 

 sects, which it follows, by the use of oil emulsion or some other scale- 

 cide. Freedom from scale and hence from sooty mold, will elimi- 

 nate in large part the necessity of washing the fruit, a procedure 

 which increases the amount of rot. 



FRUIT ROTS, OR SHIPPING ROTS. 



The several fruit rots, or shipping rots as they are also known 

 because of their developing during shipment, qnite probably cause 

 the greatest financial loss of any of the citrus diseases. They \v\\\ 

 even take first place over scab, since all rotted fruit is a dead loss, 

 but much of that which is scabby can be sold in the lower grades. 

 The amount of rot varies from season to season, depending upon 

 moisture conditions, and other factors. The time of year, or in other 

 words the maturity of the fruit, has an inijiortant bearing on the 

 prevalence of rot, the percentage running high, as a rule, during 

 the latter part of the shipping season, when much of the fruit is 

 overmature. The actual loss will vary from one to fifty per cent 

 ::;f each shipment, possibly averaging five per cent for the season, 

 wild oranges excepted, which have a much higher percentage. In 

 estimating the loss, there nuist be taken into account not only the 

 actual rot, but the lowering of price of the remaining sound fruit, 

 the cost of repacking at New York, and the damage to the reputa- 

 tion of a brand showing heavy rot. 



Several fungi are involved in the rotting, so that distinct types, 

 stem-end rot, blue mold, anthracnose, and blossom-end r'ot are dis- 

 tinguished. 



STEM-END HOT, DII'LODIA ROT.' 



This rot may attack the fruit at any tim(> from ])artia] maturity 

 to delivery on the market. Certain groves oi' l)l()('ks of trees ai'c 

 much more subject to it than others, due in part at least to the greater 

 abundance of the causal fungus on dead wood in the trees. 



In a great majority of cases infection occurs at tlie stem end 

 of the fruit, and hence the common name. A soft i-ot ensues, in- 

 creasing very rapidly in extent until the entire fi-iiit is involved. 

 The rot works through the eenti'iil pith portioti of the fruit. api)earing 



