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BULLETIN 1118, U. S. DEPARTMENT OF AGRICULTURE. 



grapefruit are likely to be misleading. Rough-lemon and sour- 

 orange nurser}^ trees are exceedingly susceptible to scab infection 

 and are equally affected if not more severely attacked during the 

 hot rainy summer season than is the case in the spring. That this 

 condition exists is corroborated by letters on file in the Office of Fruit- 

 Disease Investigations from five of the larger commercial nurseries 

 in Florida. 



The United States Department of Agriculture maintains a nursery 

 of rough-lemon, sour-orange, and grapefruit seedlings at Orlando, 

 Fla., for experimental purposes. This nursery was set out in March, 

 1918. The flushes which developed during April and May of that year 



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2.— Precipitation and maximum and minimum temperatures at Orlando, Fla., during January, 

 February, March, and April, 1915 — a year of severe scab infection. 



were affected by citrus scab, but not nearly so severely as was the 

 case during the rainy simamer weather. The flush which developed 

 late in the fall was comparatively free from citrus scab, in spite of 

 foci of infection on the older leaves. Similar conditions were noted 

 in this nursery during the years of 1919 and 1920, viz, scab attacks 

 the nursery stock more severely during the ramy season in summer 

 than is the case during the spring or fall. As stated in another place, 

 the spring of 1921 was quite dry. Little or no citrus scab developed 

 in this nursery during that period. The same applies to a new seed 

 bed of similar seedlings. As soon as the rains set in citrus scab im- 



