4 82 



DISEASES OF CULTIVATED PLANTS 



fragments. On the other hand, if warm weather is suddenly 

 followed by a chill, conidia are produced in abundance. The 

 disease may appear during any period of the growth of the 

 host. 



Conidiophores gregarious or subfasciculate on large, dry, 



FlG. 144. Helminthosporium turcicum. i, portion of a 

 maize leaf with fungus ; 2, a cluster of conidiophores, two 

 bearing conidia, highly mag. 



brownish spots, septate, 150-180x6-9 /A; pale olive, apex 

 almost colourless, often nodulose; conidia spindle-shaped, 

 ends acute, 5-8-septate, pale olive, 80-140x20-26 /z. 



A difficult disease to check, perhaps burning the stubble 

 after corn has been gathered, if practicable, would to a certain 

 extent prevent future infection. Rotation of crops, however, 

 would be the most certain method, and as maize impoverishes 

 che soil to a great extent, this course is advisable. 



Bancroft, Proc. Roy. Soc. Queensland, 8, p. 108. 



Helminthosporium teres (Sacc.) sometimes proves destruc- 

 tive to the barley crop, causing the leaves to shrivel and die. 

 It forms rather large olive blotches on the leaves. 



