Feb. 9, 1924 
Effect of Fertilizers on Stem Rust of Wheat 
347 
plats at University Farm. By the method described below a severe 
epidemic was obtained each year. 
Common barberry bushes, covered with wheat straw containing 
teliospores, were grown in the field. This straw was placed around the 
barberry bushes late in the fall and was allowed to remain until the 
leaves had unfolded in the spring. Abundant aecia developed on the 
barberry leaves. Winter wheat was sown early in the fall around the 
barberry bushes. This resulted in the production of urediniospores on 
the winter wheat early in the spring. The wheat plants in the fertilizer 
plats were then sprayed with a water suspension of aeciospores from the 
barberry leaves and urediniospores from the winter wheat. The plants 
were sprayed every other day after sunset, or during the day in wet, 
cloudy weather, until a heavy epidemic was assured. In addition, 
flower pots, containing wheat seedlings, well covered with uredinia, 
were placed in the plats. Large quantities of rusted material were 
developed in the greenhouse and there held in readiness to be placed in 
Fig. i.—S cale for estimating percentage of stem rust. The shaded spots represent rust, and the figures 
represent approximately the rust percentages computed on the basis of the maximum amount of sur¬ 
face covered by rust as shown in No. 6, which represents 37 per cent of surface covered with rust pus¬ 
tules and is arbitrarily selected as 100 per cent. Other percentages are based on No. 6. (From Office of 
Cereal Investigations, United States Department of Agriculture.) 
the field at the proper time. Spore suspensions for spraying also were 
made from this material. Hand inoculations were made in the field in 
the same manner as in the greenhouse. For this purpose control rows 
of a susceptible variety were sown along the side of the plat. After the 
inoculum had been placed on the seedlings, they were covered with a 
bell jar, or inverted flower pot, for 48 hours, the soil being kept wet 
around the jar or pot during this period. 
The scale (fig. 1) used in the stem-rust investigations made by the 
Office of Cereal Investigations of the United States Department of 
Agriculture, was used in estimating the percentage of rust. 
The final percentages of rust infection were estimated just before the 
plants ripened. They were made by several experienced observers, 
some of whom did not know the disposition of fertilizers in the plats. 
The estimates made by the different individuals did not vary over 5 
per cent for any one plat. 
Estimates of the degree of lodging, the severity of stem rust on the 
peduncle, sheath and leaves, the amount of seed shriveling, and the 
