The effect of eyespot (Cercosporella herpotrichoides Fron.) on wheat and the influence of nitrogen on the disease

The effect of eyespot throughout the season on wheat receiving different amounts of nitrogen was studied in pot experiments. Plants inoculated in December showed chlorosis of outer leaves in February. Among plants with high nitrogen, eyespot killed 11%, caused straggling of 31% and whiteheads in 14% of the surviving ear-bearing straws, reduced yield of straw by 8% and of grain by 16%. The loss in straw yield was due to reduction in plant number, that of grain was about half due to reduction in number of ears and half to production of lighter grains. Among plants with low nitrogen the disease killed 23% of the plants, caused straggling of 86% and whiteheads in 18% of the surviving ear-bearing straws, and reduced yield of straw by 23% and of grain by 44%. The loss in straw yield was due to death of plants, that of grain was about two-thirds due to the production of fewer ears and one-third to that of lighter grains. In the high-nitrogen series the number of shoots at the time of maximum tillering was reduced by 29%; in the low-nitrogen series the disease caused reduction in height, a very uneven crop, delay in ear and anther emergence, and an increase in tail corn from 4% in the controls to 30% in the inoculated plants. All inoculated plants became infected, but those receiving high nitrogen had only 49% of the ear-bearing straws with severe lesions at harvest, while those receiving low nitrogen had 86%. The larger number of tillers produced when nitrogen was applied may have enabled the less severely diseased shoots to survive and bear ears while the most severely infected died.