202 FIELD CROPS 



favorable to its development. The stem rust of oats is very 

 similar to the stem rust of wheat, appearing as black spots 

 or blotches on the leaves and stems shortly before the grain 

 ripens. The stem rust is rather less common than the leaf 

 rust, but when it occurs it injures the crop more seriously. 

 Both these rusts are very common in the South, appearing 

 practically every year. In the Northern states, where 

 climatic conditions are more favorable to the growth of oats, 

 rust injury is decidedly less frequent. It is most likely to 

 occur in wet seasons, when the growth of the crop is rank. 

 Oats on rich, wet land are particularly likely to be damaged 

 by rust. The conditions favorable to the development of 

 this disease are soft, rank growth; damp, cloudy weather or 

 heavy dews; and land which is particularly retentive of 

 moisture. No effective remedies have yet been discovered. 

 Some varieties or strains of cats appear to be more rust 

 resistant than others, and plant breeders are attempting to 

 develop this quality to a still greater degree. The best pre- 

 ventive measure is to sow this grain on well drained land 

 which is not too rich, thus avoiding as much as possible the 

 danger of too rank growth and the moist conditions so con- 

 ducive to the development of rust. 



Oat smut is also of two kinds, the loose and the covered. 

 These smuts differ but little in appearance, and their life 

 histories are practically the same. The spore enters the 

 growing point of the plant about the time germination takes 

 place, and the slender threads of the smut fungus develop 

 in the tissues of the plant along with its natural growth. 

 The smut reaches its mature form in masses of black, powdery 

 dust, or .spores, which replace part or all of the oat head. In 

 loose smut the chaff as well as the grain itself is replaced 

 by the smut masses, while in covered smut the chaff remains 

 in its natural state, enclosing the smut spores. Smutted 



