MARKET DISEASES OF FRUITS AND VEGETABLES 7 



SCAB 



(Sphaceloma fmvcettii Jenkins 5 ) 



Scab is found chiefly on Temple oranges and on grapefruit. It 

 attacks tangerines to a lesser degree and is sometimes found affecting 

 King oranges, Tahiti (Persian) limes, and some tangelos. It is ex- 

 tremely rare on sweet oranges and kumquats. Lemons are susceptible 

 but are generally grown where climatic conditions prevent scab de- 

 velopment. The disease occurs on fruit in Florida and Texas and in 

 the West Indies but has not been reported from California. It is 

 believed to have been introduced into the United States on Satsuma 

 orange trees from Japan and is widely distributed over the world in 

 citrus-growing countries where climatic conditions are favorable to its 

 development. On the fruit the earliest symptoms are small raised 

 areas in the rind, which are whitish at first but later assume a pinkish 

 or tan color. Scab occurs on leaves, twigs, and fruits but attacks these 

 parts only while they are young. On all three it starts in much the 

 same way. namely, as small pale-yellow to orange-colored elevated 

 spots, which as they grow older become irregular scabby areas or warty 

 protuberances ranging in color from drab to dark olive gray. These 

 protuberances may be single or they may coalesce to form large raised 

 patches of gray or tan-colored scab. Fruits severely infected while 

 young may become misshapen because of excessive development of the 

 warty outgrowths. On mature grapefruit the skin around the scabby 

 areas tends to remain green. 



On the fruit, the disease affects only the skin but makes the fruit 

 unsightly and therefore less valuable on the market. Since infection 

 takes place only when the fruit is small there is no danger of new 

 infection in transit or storage. Areas affected by scab are not invaded 

 by other fungi. 



As scab is a field disease, it can be controlled by spraying with bor- 

 deaux mixture. It is also desirable to cut out and burn all infected 

 sour orange and rough lemon sprouts from rootstocks of grove trees. 



(See 21, 37, !fi, 1*3, 69, 87. 96. 99. 136, 137.) 



SCLEROTIUM ROT 



(See Oranges, Sclerotium Rot, p. 31.) 



SEPTORIA SPOT AND STAIN 



(See Oranges. Septoria Spot and Stain, p. 31, and pi. 15. B.) 



SPRAY INJURY 



(See Oranges, Spray Injury, p. 32. and pis. 6, D, and 11, C-E.) 



STEM -END ROT 



(Phomopsis citri Fawc. 6 and Diplodia natalensis Pole-Evans 7 ) 



OCCURRENCE. SYMPTOMS. AND EFFECTS 



Stem-end rot caused by Phomopsis citri and Diplodia natalensis is a 

 destructive and widely distributed disease of citrus fruit in the Gulf 



5 Perfect stage, Elsinoe faiccetti Bitanc. and Jenkins. 



6 See footnote 4. 



7 Perfect stage, Physalospora rhodina (Cke.) Berk, and Cke.' 



