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Journal of Agricultural Research voi. xxvii, No. 6 
REVIEW OF PREVIOUS WORK 
A summary of what has been published on the factors which predispose 
to or protect plants from disease would comprise many bulky volumes. 
It should be axiomatic that different host plants and pathogenes are 
affected differently by environmental conditions. It is difficult or im¬ 
possible, therefore, to establish universally applicable principles, and, 
for this reason, only the most relevant literature is reviewed in this paper. 
Little (75), in 1883, stated that low, rich soils and heavy manuring, 
especially with nitrogenous manures, predisposed wheat to rust. Ander¬ 
son (j), in 1890, and Bolley (5), in 1889, expressed a similar opinion. 
Anderson found hard, flinty wheats resistant to rust. He thought 
resistance due possibly to the large amount of silica in such plants, 
and advised against the use of excessive quantities of nitrogenous fertili¬ 
zers. He recommends that salt, iron sulphate, and lime be used to 
prevent rust. 
Petermann ( 22 , p. 15-16) reported in 1902 that wheat manured with 
superphosphate was very badly rusted, while that fertilized with volcanic 
slag was almost free. He thought the difference in resistance was due to 
differences in the strength of the cell walls. 
In 1903, Ward (, 58 ), showed lack of minerals did not confer immunity 
from Puccinia dispersa Erikss. on bromes. 
Remer (24) observed in 1903 the effect of fertilization on cereal rusts 
in Silesia. He concluded that even a slight excess of nitrogen predisposed 
cereals to rust. Stable manure applied to soil previously devoted to 
clover predisposed wheat and oats especially. He thought that ex¬ 
cessive vegetative vigor, consequent lodging, and greater leaf surface 
favored the development of rust, and that acid phosphate usually in¬ 
hibited its development on plants grown in soils in which there was not 
too much nitrogen. Potash did not predispose his cultures to rust. 
McAlpine (16), in 1906, found that the most vigorous plants often 
were most severely rusted and that early maturity favored escape from 
rust injury. Johnson (74), in 1911, stated that wet soils and luxuriant 
growth predisposed timothy to the timothy rust, P. graminis phleipra- 
tensis Erikss. and Henn. Montemartini (20) stated that starved plants 
were immune from rust and that phosphates always increased resistance. 
Freeman and Johnson (8) cite general observations on the apparent pre¬ 
disposing effect of nitrogenous fertilizers. 
Biffen (4), in 1912, found P. glumarum most abundant on plants which 
had received a complete fertilizer. The amount of rust decreased with 
a decrease in the amount of fertilizer used. 
Comes (7) states that nitrogen predisposed plants to rust, while non- 
nitrogenous fertilizers, especially potash, tended to increase resistance. 
He found that the concentration of organic acids was lowered, and that 
resistance to infection was proportionately lowered. 
Spinks (30) studied the effect of nutrient salts on the susceptibility 
of wheat to P. glumarum and Erysiphe graminis DC., and of barley to 
E. graminis. He concluded that heavy applications of nitrogenous 
fertilizers increased the susceptibility of wheat to stripe rust, and of 
wheat and barley to powdery mildew. Potassium salts increased the 
resistance but did not counteract the effect of large amounts of nitrogen. 
Spinks concludes, however, that a highly resistant variety tends to 
remain resistant even when heavily fertilized with nitrogenous manures. 
Voelcker’s results (37) were essentially similar to those of Spinks. 
