DISEASES OF CULTIVATED PLANTS 593 



5. The varieties with straight, stiff leaves are affected less 

 than those which have weak foliage; and the varieties which have 

 thick skinned leaves, or whose leaves are either smooth, allowing no 

 holding-place for the spores, or very hairy, holding the spores but 

 at such a distance from the leaves that they fail to germinate, or 

 germinating fail to infect the leaves, are the best to plant. 



6. Don't sow wheat on stubble-land, where rust has been 

 abundant, for the stubble is often black with winter spores, or is 

 capable under certain conditions of lasting green and thus allowing 

 a place of development to the Uredospores. 



7. It seems that the red wheats are least affected, while the 

 white varieties, notably Velvet Chaff, are most subject to rust. 



8. Poor drainage and an excess of nitrogen in the soil seem 

 also to aggravate the evil. (Idaho E. S. B. 11.) 



DISEASES OF STAPLE PRODUCTS. 



BEET DISEASES. 



Leaf Spot of the Beet. This disease is one of very wide distri- 

 bution. It has long been known both in this country and in Europe, 

 and it probably occurs in all regions where beets are grown even to a 

 limited extent. It is a well-known disease of the red garden beet, but 

 many of the garden varieties are so resistant that the disease is not 

 there a matter of great concern. Observations in New York state 

 indicate that it is much more injurious to sugar beets than to the red 

 varieties. For this reason it needs to be brought to the special atten- 

 tion of those interested in the culture of sugar beets. 



The name well denotes the appearance of the disease, at least 

 in the early stages. It begins as small brown spots with a reddish 

 purple margin, these spots being scattered irregularly over the leaf. 

 The spots become ashen gray at the centers, with the border as be- 

 fore ; and they may become so numerous as to cover a large portion 

 of the surface of the leaf before there is any general discoloration 

 of the blade. In time, however, the blade shows a parched appear- 

 ance, begins to blacken gradually from the distal portions towards 

 the stalk, and finally the whole leaf is black and crisp. As soon as 

 the leaves begin to appear parched and dry, they stand more nearly 

 upright on the crown, and a whole field badly affected with this 

 disease makes a very characteristic appearance. The individual 

 blades that are badly affected are somewhat curled or rolled. (Cor- 

 nell E. S. B. 163.) 



The outer or older leaves are of course first affected, and after 

 the leaf stalks wilt these leaves are shed. In the meantime the plant 

 is endeavoring to supply this deficiency of leaves by continuing to 

 develop new ones from the center, or from the bud. 'in consequence 

 of this, the crown becomes considerably elongated. If this elonga- 

 tion is very marked, the roots are abnormally small, and much of the 

 energy of the plant is evidently directed to saving itself. Even 

 where the leaves are much less injured, it is undoubtedly a matter 

 of economy to resort to preventive measures. 



Sorauer has stated that the leaf spot fungus is not confined to 



