Nov. 3, 1923 
Helminthosporium Disease of Wheat 
slight bimodal tendency, but this phenomenon has been discounted on 
the basis of experimental error and because the temperature optimum for 
the Helminthosporium disease probably is not a decidedly critical point, 
but a rather limited range. 
As Dickson gives only averages of a number of experiments, it can not 
be determined whether he is dealing with an actual or an apparent bimodal 
condition in Marquis wheat. It would seem that the interpretation of a 
double apex in a curve which represents the average results of a number 
of individual experiments must be considered from at least two angles: 
(1) As the possible expression of shifting optima in the several experi¬ 
ments making up the average, and (2) as the expression of a true bimodal 
reaction. In the second case we would, and in the first case we would not, 
expect to find the bimodal character showing up in the individual experi¬ 
ments. Therefore, an analysis of the data from the individual experi¬ 
ments would seem necessary to interpret any bimodal tendencies. It 
would seem, therefore, that Dickson's average data may represent only 
a shifting optimum. 
While the data herein presented indicate that the date of seeding in¬ 
fluences the severity of the Helminthosporium disease in winter wheat, 
positive recommendations concerning a general seeding practice can not 
be offered until field sowings have been made with spring wheat and bar¬ 
ley, and until more work has been done on the susceptibility of the plants 
under different conditions and at different stages in their development. 
This seems especially true when it is considered that spring wheat and 
barley develop during a period of rising temperatures, whereas winter 
wheat is first subjected to a period of descending temperatures, then to 
low temperatures fairly continuously, and later to rising temperatures. 
Obviously, it is not safe to apply the results of field experiments with 
winter wheat to spring wheat or barley by recommending early planting 
of the latter two cereals, but it does seem safe to assume that the late 
planting of winter wheat, when other more important factors are not 
affected adversely, will tend to reduce the amount of Helminthosporium 
injury to the underground parts. Proper soil drainage also should aid 
in reducing the disease. 
SUMMARY 
(1) Helminthosporium sativum P. K. and B. is a vigorous parasite, 
under certain conditions, on all parts of wheat and barley plants. 
(2) H: sativum has been claimed by certain workers to be the direct 
cause of the rosette disease of wheat (sometimes called footrot and 
take-all), but as yet there is no positive proof of this causal relation. 
(3) In certain districts, especially in the spring wheat belt, the Helmin¬ 
thosporium disease is at times very severe. 
(4) Controlled greenhouse experiments and field experiments were 
made to study the influence of soil temperatures and soil moistures 
on the infection of the subterranean parts of winter and spring wheat 
and barley plants. 
(5) In these studies fourteen constant soil temperature experiments 
and one controlled alternating soil temperature experiment were con¬ 
ducted in the Wisconsin soil-temperature tanks. Three soil-moisture 
experiments were made in the greenhouse, one of which was conducted 
in conjunction with a soil-temperature series. 
