LEMON AND ORANGE SCAB 311 



dusky, finally black. Trees growing in low, moist situa- 

 tions are most subject to scab; in fact, the spread and 

 development of the fungus requires the almost constant 

 presence of moisture in the air. The sour orange {Citrus 

 bigaradid) is especially susceptible to this disease. 



Preventive Means. — Spraying with ammoniacal solu- 

 tion of copper carbonate is effectual; so is Bordeaux 

 mixture, but the latter is more or less injurious to the 

 foliage and fruit. Spraying should commence when the 

 fruit is just set, and continued at intervals. 



All diseased fruit, whether on the ground or still on the 

 tree, should be collected and burned. 



Sour orange-trees should be cut down, also all shoots 

 from sour stocks. 



In planting avoid low-lying, damp situations. 



The fungus causing this disease has been referred to by 

 the authors as Cladosporium sp. I have added the specific 

 name citri, not for purposes of priority, but for convenience 

 of reference to the diagnosis in the systematic appendix. 



This Cladosporium species is evidently quite distinct 

 from Cladosporium elegans, Penzig, which forms arid, 

 brown spots on living leaves of oranges in Italy. 



Lamson-Scribner, Bull. Torrey Bat. Club, vol. xiii. p. 

 181. 



Swingle and Webber, U.S. Dept. Agric, Bull. No. 8, 



TOMATO LEAF RUST 



(Cladosporium fulvum, Cke.) 



This disease often proves destructive to tomatoes both 

 in Europe and the United States, especially where the 

 plants are grown under glass. The leaf is the part most 



