The Take-all Disease of Cereals and Grasses 19 



roots a considerable amount of soil is often pulled up with them, giving 

 them a characteristic clubbed appearance. 



Under greenhouse conditions the take-all pathogene has been observed 

 to cause lesions on the roots of wheat seedlings within fourteen days after 

 planting, and to cause the death of the seedlings within another week. 



On culms and heads. — The first symptoms to be observed in wheat 

 plants under field conditions appear immediately after the plants have 

 entered the jointing stage and when they are from six to ten inches high. 

 These symptoms consist of a yellowing of the leaves and a dwarfing of 

 the plants. (The earliest date of observing these symptoms at Ithaca is 

 May 22.) The plants that are most severely affected soon die. By 

 flowering time the diseased areas in the fields are strikingly characterized 

 by the whitish color and the stunted stature of the plants contained in 

 them. These areas are often 15 feet or more in diameter and are usually 

 circular in outline. They contain from one to many plants. Their 

 edges often overlap in badly infected fields, so that one may walk across 

 such a field without leaving them. In some fields the disease occurs for 

 several feet along the drill rows. The individual plants are usually dead 

 and ashy white in color, and in the center of large areas are either killed 

 out or dwarfed to a few inches in height. Most of the diseased plants 

 are dead by flowering time, and on an average not more than one head 

 per plant is developed. 



The whitish color of the plant suggests the name white heads which is 

 used by some writers to designate the later stage of this disease. A char- 

 acteristic symptom is the marked reduction of the normal number of 

 tillers, many of which die soon after their formation. 



There is no striking change in the symptoms from the time of flowering 

 to harvest. However, the diseased leaves and culms may become sooty 

 due to the growth of saprophytic species of Cladosporium and Mucor. 

 The " white head " stage only was observed in rye. Rye shows no chlo- 

 rotic symptoms until after flowering, and therefore exhibits little or no 

 stunting and only a moderate shriveling of the kernels. 



The symptoms in barley as reported by Hori (1901) in Japan differ 

 from those of wheat in that they often appear within thirty to forty days 

 after the winter barley is sown. This stage is spoken of as the yelloiv-leaf. 

 The other symptoms on barley are essentially like those on wheat. 



On Agropyron repens the chlorosis and dwarfing were not conspicuous, 

 but many lesions were found on the perennial rootstocks. 



Signs 



The first signs appear very soon after the chlorotic symptoms (May) 

 and consist of a mat, or plate, of brown mycelium which extends from the 

 root upward for several inches above the crown. The mycelium is in the 

 leaf sheaths and between the culm and the inner leaf sheath, where it 



