54 MISC. PUBLICATION 4 4 0, U. S. DEPARTMENT OF AGRICULTURE 



may become brown and shriveled. The disease is of considerable 

 economic importance in Florida and it is occasionally found affecting 

 Florida celery on the market. It also affects carrot, dill, and parsley, 

 as well as a wide variety of other plants in Florida. What is ap- 

 parently the same disease has been reported on celery in several other 

 States. 



The most important mosaic disease of California celery is the 

 western celery mosaic. It differs from the southern celery mosaic in 

 that the causal virus can be transmitted only to members of the 

 parsley family. Although the two diseases have many symptoms in 

 common they differ in some respects. Thus the rust-colored necrotic 

 spots and streaks that are characteristically present on the upper 

 surface of older leaves on plants affected with the western celery 

 mosaic have not been reported for southern celery mosaic. At the 

 same time the brownish water-soaked spots and sunken streaks found 

 on the leakstalks of plants affected with southern celery mosaic have 

 not been observed on plants affected with western celery mosaic. 



Calico, crinkle-leaf, and yellow spot, all of which produce chlorotic 

 spots on the leaves of affected plants, have likewise been described 

 from California celery; and poisonhemlock ringspot has been 

 experimentally transmitted to celery. 



There are several other virus diseases found on celery, carrots, and 

 related plants. Thus yellows, caused by the aster yellows virus, is 

 frequently of importance on carrots in the field. Although attempts 

 to transmit the virus to celery have been unsuccessful it has been 

 transmitted to anise and dill, and is responsible for a yellows disease 

 of parsnip. In California, however, celery is affected with a yellows 

 disease that can be transmitted to aster, carrot, parsnip, parsley, and 

 other plants. The disease has been called California aster yellows to 

 distinguish it from aster yellows, which as noted above cannot be 

 transmitted to celery. Finally, there is the curly top disease in the 

 States west of the Rocky Mountains, which affects sugar beets and 

 a wide variety of other crop plants including carrot and which has 

 been experimentally transmitted to celery; and there is the spotted 

 wilt disease found affecting celery in California. 



Control of the several virus diseases is based upon such measures as 

 eradicating the weed hosts that perpetuate the disease from season 

 to season and serve as the source of virus infection for the new crop, 

 controlling the insect carriers, and planting resistant varieties 

 or strains. The virus diseases are of importance on the market only 

 when an attempt is made to market plants seriously affected with 

 this kind of disease in the field. 



(See 168, 174, 184, 185, 186. 196, 199. 208. 209, 210, 211. 216, 218, 

 219, 220.) 



PHOMA ROOT ROT 



(Phoma apiicola deb.) 



OCCURRENCE. SYMPIOMS. AND EFFECTS 



Phoma root rot lias been reported from Michigan, Ohio, and New 

 York. Although found in plantings only on celery the disease has 

 been produced by artificial inoculation on caraway, carrot, parsley. 



