Mar. io, 1923 
Rosette Disease of Wheat and Its Control 
795 
The outstanding result of the variety tests is that the great majority 
of winter wheat varieties are resistant to or immune from rosette. While 
this ratio between resistant or immune and susceptible varieties is 
unusual, it is paralleled in the cases of the Lahaina, Sereh, and Fiji 
diseases of sugar cane. 
INFLUENCE OF SEEDING DATE 
In order that information might be obtained on this phase of the 
problem, a series of sowings was made during the fall of 1919 on land 
which developed uniform rosette infestation during the previous season. 
Two susceptible strains of Harvest Queen wheat (Salzer’s Prizetaker and 
white-chaffed Red Cross) were used in the experiment. Each variety 
was sown on five different dates, except that, through error, Early May 
wheat was sown in the place of the first sowing of the white-chaffed Red 
Cross. 
Each sowing consisted of a single strip 54 inches in width and 6 rods 
long. All seed was sown with an 8-spout disk drill. Seed was treated 
with formaldehyde and sown at the rate of 6 pecks per acre on Sep¬ 
tember 18 and 24, October 4 and 16, and November 18. The results 
are given in Table IX. 
t ■ 
Table IX. —Percentage of rosette disease developed in strains of Harvest Queen wheat 
(Salzer’s Prizetaker and white-chaffed Red Cross) sown in plots 54 inches by 6 rods, on 
jive different dates in IQIQ, at Granite City, III. 
Strain of Harvest Queen wheat. 
Percentage of disease in plots seeded on different dates* 
Sept. 18. 
Sept. 24. 
Oct. 4. 
Oct. 16. 
Nov. 24. 
Salzer’s Prizetaker. 
. 95 
No sowing. 
90 
78 
90 
78 
79.0 
73-8 
4-5 
0. 28 
White-chaffed Red Cross. 
In the first four sowings there was normal fall emergence, but from 
the sowing of November 18 emergence did not take place until spring. 
In the first sowings there was a little Hessian-fly injury in the fall. 
In the October 16 sowing considerable winterkilling took place. Both 
of these complications made it necessary to calculate the amount of 
Hessian-fly and frost injury in other neighboring plots not affected by 
the rosette disease in order that corrections might be made in the 
rosette disease plots. 
Except in the November 18 sowing, a high percentage of disease 
developed in all the plots. Reference to Table X will give the exact 
percentage of the disease in each plot after corrections have been made 
for injury by Hessian fly and frost. It is quite evident that the date 
of sealing influences the development of the rosette disease, but this 
relation seems not to be of such nature as to permit economic application. 
It is remarkable that the disease should be so slight in the sowing that 
did not emerge until spring (PI. 8, B). 
The result of this field experiment shows very conclusively, on the 
basis of the November 18 sowing, that the problem is largely a seasonal 
one, and it bears out the general contention that the disease can not 
be produced successfully in a high percentage of plants under ordinary 
greenhouse conditions or in the field out of the regular season for the 
winter wheat plant. 
