2 BULLETIN 1118, U. S. DEPARTMENT OF AGRICULTURE. 



is important. It is not uniformly serious throughout the citrus- 

 growing sections of the Gulf States, but in certain well-defined 

 localities scab is of the greatest importance. 



The damage done to leares on bearing trees is more unsightly 

 than harmful (Pis. I and II; PL III, Fig. 2). There is no tangible 

 evidence to show that the functioning power of moderately affected 

 leaves is seriously impaired. 



In orchards where a large proportion of scab has recently developed, 

 especially where the infection is serious enough to cause a marked 

 distortion of the fruit (PI. Ill, Fig. 1), the dropping of fruit recently 

 set is considerably greater than where scab does not occur in serious 

 proportions. A large percentage of this dropped fruit is distorted 

 by scab. In addition to the rather intangible financial loss brought 

 about by the abnormal early drop of green fruit due to scab infec- 

 tion, a more tangible loss is occasioned by scabby fruit reaching 

 maturity. A badly blemished fruit is a cull; a slightly blemished 

 fruit has to be sold by the producer at a discount of at least 50 cents 

 per box in years of fair prices. An average estimate made by con- 

 servative business men familiar with the citrus industry covering 

 the scab losses to citrus growers in Florida is about 1,000,000 boxes 

 infected annually. With the production of citrus fruits in Florida 

 increasing rapidly, the average annual losses from scab are likely to 

 increase. Under the most favorable circumstances the cost of pro- 

 duction of grapefruit, kid-glove oranges, tangelos, and lemons of first 

 quality is greatly increased in districts where scab is a serious factor 

 and has to be controlled by sprays. 



The damage done to groves before they come into bearing is con- 

 siderable, but usually not sufficiently great to render control measures 

 imperative. Nevertheless, a reasonable investment in protective 

 measures may be used to financial advantage. 



Scab is the only parasitic fungous disease of consequence occurring 

 in the citrus nursery. There it is extremely serious. It produces a 

 very marked stunting effect upon seedling stocks for budding (PI. IV), 

 frequently reducing the growth by about 40 to 50 per cent. Where 

 citrus scab is held under control vigorous seedlings are sufficiently 

 large to be budded after having been transplanted to nursery rows 

 for a growing season. Where the disease occurs in quantity and is 

 not held in check by treatment, seedlings may require from 2^ to 3 

 or more years to make sufficient growth to be budded. This disease 

 is of such serious consequence to rough-lemon and sour-orange nursery 

 stock that nurserymen are in search of a desirable stock immune to 

 citrus scab. Grapefruit leaves are most susceptible to infection as 

 they begin to expand. They become entirely resistant to infection 

 by the time they reach a half inch in width. Fruit is susceptible 

 until it is about three-fourths of an inch in diameter. 



