14 



The Bulletin. 



other. The Iron variety of cowpea possesses a high natural resistance 

 to the wilt disease as well as to nematode injury. Certain hybrid 

 varieties, such as the Brabham, have been bred with a similar resistance. 

 Control. — Avoid spreading the disease by means of infected soil or 

 manure. Infected hay, either fresh or cured, is a source of danger to 

 the manure. Cowpea seed from an uncertain source may be treated 

 with formaldehyde solution, one pint of full strength or 40 per cent for- 

 maldehyde in forty gallons of water, before planting as a precaution 

 against spore contamination ; but it is not certain that this is a common 

 source of danger. Plant the Iron or' some other resistant variety of 

 cowpea on infected land. Tests in North Carolina for six years in 

 comparison with thirty varieties give the Iron cowpea a rank of 

 eighth in seed production and of first in hay production. 



GRAIN RUSTS. 



This discussion has reference to four species of rust, (1) the stem 

 rust or black rust of wheat, oats, and rye (Puccinia graminis) ; (2) the 

 leaf rust or orange rust of wheat (Puccinia rubigo-vera tritici) ; (3) 

 the leaf rust or orange rust of rye (Puccinia rubigo-vera secalis) ; and 

 (4) the leaf rust or crown rust of oats (Puccinia coronata). Besides 



Fig. 6. Leaf Rust of Rye. The granular appearance of these summer spore pustules does not show 

 distinctly in the photograph. 



these, barley is attacked by the stem rust named above, and in addition 

 by a leaf rust ; and corn is attacked by still another species. _ These last 

 are omitted from discussion because of their less economic importance. 



Any one of the four forms under discussion may be expected on the 

 appropriate crop in any section of the State, although there is consid- 

 erable seasonal and local variation in the amount of each. 



Symptoms. — Small, elongated spots with a powdery appearance and 

 a reddish-yellow or orange color, are the conspicuous features of these 

 rusts. Sometimes the term "rust" is applied erroneously to any disorder 

 that produces discoloration of the leaves. The stem rust develops on 

 stems and sheaths more frequently than on the blades; and in its later 

 development on maturing plants produces prominent granular black 



