188 

 Septoria Diseases 



Of these diseases there are two. One attacks the leaves of the wheat 

 and is known as speckled leaf-blotch, the other appears especially on the 

 glumes and is commonly known as glume blotch. Little is known of their 

 early occurrence in Illinois. Between June IS and 28, 1010, three slight 

 infections and one of 10 per cent were found by workers of the United 

 States Department of Agriculture, but the localities are not known. The 

 seriousness of these diseases emphasizes the need for effective control 

 measures. 



Speckled Leaf-Blotcii 

 Caused by Septoria tritici Desm. 



Every season there appears on the leaves of wheat plants spots of 

 discolored, diseased tissue. In unusual seasons this spotting may become 

 so severe as to injure all of the leaves seriously and to kill many of them. 

 The disease first appears as a more or less oval brown spot. Later, 

 several spots may grow together, occupying a large part of the leaf sur- 

 face. As the spots grow older, they show tiny black specks irregularly 

 distributed over them. The presence of the specks— which are the fruit- 

 ing bodies of the fungus causing the disease — gives the disease its name. 



There are no early reports of the presence of speckled leaf-blotch in 

 Illinois, but in 1919 S. C. Chandler collected it at Ashley, Washington 

 county, April 14, and in Perry county April 10. These two collections 

 constitute the first actual record of this leaf blotch in Illinois. During- 

 1922 it was found in Saline county, but the abundance of leaf rust that 

 season probably prevented its being noticed elsewhere. In 1923 leaf 

 rust was markedly less abundant, and reports of speckled leaf-blotch 

 were proportionately more numerous. The disease was already prev- 

 alent to a considerable extent when field work was begun, as is shown 

 by our first report of it, a 20-acre field of Red Wave in Madison county 

 having an infection involving 75 per cent of the plants. Table 20. Fully 

 25 per cent of the leaf surface was occupied by spots, and the lower 

 leaves of the plants were so seriously infected as to have the appearance 

 of "firing." From that time on, the disease was found to be prevalent 

 and abundant wherever looked for. Speckled leaf-blotch is now known 

 to occur in 23 counties distributed widely over the state, as shown on 

 Map 0. 



The infections found in wheat fields in the 23 counties are shown 

 in Table 20, from which it appears that 89.4 per cent of the wheat plants 

 were diseased, and that 32.2 per cent of the leaves on each diseased 

 plant showed leaf blotches. On this basis it would appear that this 

 disease injured 28.78 per cent of the leaves of the wheat plants grown in 

 the state in 1923. It is not to be supposed that such a marked injury 

 can result otherwise than in an appreciable reduction both in the quality 

 and quantity of grain produced. 



