DISEASES OF PLANTS. 905 



DISEASES OF PLANTS. 



Some fungus diseases of beets, B. D. Halsted {N'ew Jersey Stas. 

 Bnl. 107, pp. 13, figs. 5). 



Syno2)sis. — The author reports upon beet scab, root rot of beets, leaf spot, beet rust, 

 white rust, and downy mildew. 



Beet scab (pp. 3, 4). — The ideuHty of the scab of beets and potatoes^ 

 is mentioned, and the necessity of avoiding the i)lanting of one crop 

 where a diseased crop of the other has previously grown. 



Boot rot of beets (pp. 4-6). — While examining a store pit of beets a 

 fungus was obtained which affected the roots, causing them to be 

 slightly shrunken and almost coal black in color, this discoloration 

 sometimes extending fully to the center of the root. The surface or 

 affected part was dotted with minute specks, which upon examination 

 proved to be the pycnidia of a species of PhyJlosticta. When placed 

 in moist cloths and kept warm the young patches on the diseased roots 

 soon develop the pycnidia in abundance. It was noticed that the fun- 

 gus easily j)enetrates the cloth and develops the pycnidia on its upper 

 surface; and this fact was taken advantage of by the author to secure, 

 in a comparatively easy way, pure cultures of the fungus. Two years 

 before a Phyllosticta was found upon the leaves of garden beets, and a 

 comparison of the pycnidia taken from the roots in question and com- 

 pared with those on the leaves showed that they are probably the same 

 species. It was noticed that the beets in the storage pit in several 

 instances still had adhering to them shreds of old leaves, and in some 

 cases the patches of decay were located beneath such closely adhering 

 leaves. Healthy roots obtained from a field where no Phyllosticta was 

 found on the foliage were placed in a box and surrounded with fresh 

 leaves obtained from a field at a considerable distance. In 10 days 

 several diseased patches developed upon the surface of the beets and 

 appeared the same as those previously studied. As the leaf is more 

 susceptible to the disease than the root the author thinks a practical 

 preventive of the spread of the disease to the root may be secured by 

 exercising care in the removal of all foliage before roots are stored. 



Beet leaf spot (pp. 7-11). — This is a leading fungus disease of the beet 

 in i>rew Jersey and is caused by Gercospora beticola. It seems to affect 

 all varieties of the beet, and makes no distinction between the early and 

 later planted ones. Its appearance uj)on the leaves is first noticed by 

 the presence of small, light, a.shy colored spots, which later often become 

 holes by the disappearance of the tissue previously killed by the fungus. 

 During the past season field experiments were made with fungicides for 

 the prevention of this disease. The ones tested were Bordeaux mixture 

 and ammoniacal copper carbonate, each being used in three strengths. 

 The Bordeaux mixture full strength was made from freshly slaclced 



» North Dakota BuL 4 (E. S. E., 3, p. 619). 



