36 TECHNICAL BULLETIN 17 



An attempt was made to check up the moisture relations of the 

 disease under field conditions. In a series of six square-rod plots, three 

 were planted to barley and three to wheat. The north half of the barley 

 plots was planted with Manchuria and the south half with Lion; the 

 north half of the wheat plots was planted with Marquis, the south with 

 Bluestem. A field drill was used for planting. Several days before 

 planting, the soil was inoculated by applying //. sativum grown on 

 sterilized wheat seed. One half gallon of the culture was applied to 

 each square rod. After the seed was planted, one of the barley plots 

 and one of the wheat plots was sprinkled for ten minutes each morning 

 and evening, a second of each was sprinkled for five minutes each morn- 

 ing and evening, and to the third no water was added. During the 

 first part of the season, very little infection appeared on any of the 

 plants except Lion barley. The weather was very cold during the first 

 two weeks after seeding and scarcely any infection occurred. There 

 was no seedling blight on the unwatered plot, very little on the moder- 

 ately watered plot, and only a moderate amount on the heavily watered 

 plot. Infection occurred mainly on the above-ground parts, resulting 

 in leaf spots and lesions on the sheaths. Less than I per cent of the 

 plants were killed. After the first two weeks, the amount of infection 

 increased very rapidly on the heavily watered plot, so that at the end 

 of six weeks 100 per cent of the plants were infected, and most of 

 them were severely attacked. On the moderately watered plot about 

 80 per cent of the plants were infected, the severity of the infection 

 ranging from light to moderate plus. On the unwatered plot, about 

 50 per cent of the plants were infected, the severity of the infection 

 ranging from light to moderate. 



The method of applying the water tended to keep a film of moisture 

 on the lower, shaded leaves, forming almost a moist chamber near the 

 surface of the soil. The sprinkling also offered a good opportunity for 

 the spores to be splashed from the soil onto the leaves. During June, 

 the weather was very hot. As a result of this combination of circum- 

 stances, the plants on the heavily watered plot were literally covered 

 with H. sativum lesions. In many cases the plants were so badly in- 

 fected at the base that they rotted off. This was not true to such a 

 marked extent on the moderately watered plot owing, probably, to the 

 fact that the surface of the soil was not kept wet enough to maintain 

 a more or less constant layer of moisture just above the surface of the 

 ground. The Manchuria barley was moderately affected, but the wheats 

 only slightly. 



