CEREALS 



353 



water-soaked sunken spots on the node 

 of the sheath. Spots upon the neck are 

 not water-soaked, and the skin does not 

 rupture until the head breaks off. Later 

 the spot becomes brownish or black, and 

 similar discoloration runs upward and 

 downward. The affected stem tissue 

 gradually extends laterally, shrinks, and 

 dies, cutting into or through the joint, 

 which results in an open wound. The 

 region above the wound becomes pale 

 and dies. 



Upon young plants leaf spots occur, 

 first brown with ashen center, later coa- 

 lescing and taking the whole leaf. If 

 the attack is early, the grain does not fill 

 at all; if late, it may partially fill. The 

 dead portion of the plant may bleach or 

 darken according to subsequent sur- 

 roundings, resulting in great variety of 

 appearances in the later stages of the 

 disease. In 70 per cent of the cases ex- 

 amined by Metcalf ^ the lowest joint of 

 the rachis was affected, and in conse- 

 quence the heads broke off at this place. 

 This gives rise to the common name 

 " rotton neck," but since the character 

 is not universal, the name is not an appropriate one. 



The chief damage results from the failure of the grain to 

 fill on the diseased stalks. An early attack may render a 



1 Metcalf, Haven, S.C. Agr. Exp. Sta. Bui. 121, May, 1906. 

 2a 



Fig. 150. — Rice blast. 

 After Fulton. 



