The Take-all Disease of Cereals and Grasses 



17 



TABLE 3. Effect on Yield of Ten Varieties of Winter Wheat Grown in Triplicate 

 Plots Resulting from the Different Degrees of Dwarfing Caused by Take-All 



seeds per head, the weight of the seeds, and the yield per plant. The 

 reduction in weight of the seeds means that the seeds from wheat plants 

 which were stunted by the disease will be so shriveled that they will be 

 worthless as grain and most of them will be so light as to be blown out 

 with the chaff in threshing. In addition to the reduction in the grain 

 yield, there is a very marked degree of reduction in the amount of straw 

 produced. This reduction in the yield of straw was apparently as high 

 as 20 to 25 per cent, on an average, for all affected wheat plants. 



The amount of reduction in the average number of heads, the number 

 of seeds produced, the weight of the seeds, and the yield per plant, did 

 not vary appreciably between the plants of different varieties which were 

 in the same class as to dwarfing or having the same degree of infection, 

 and the difference in the amount of loss between two fields or varieties 

 \\:is due to different percentages of plants occurring in the four classes. 

 ( lass 2, in which the affected plants were not stunted, contained 46.75 

 per cent of all the plants. Since there was 50.2 per cent reduction in 

 yield in this class, the total theoretical yield which would have been 

 realized if all the plants had been free of take-all was reduced 23.4 per 

 cent. In the same way, for the 23.13 per cent of all plants in class 3, 



