2 BULLETIN 1137, U. S. DEPARTMENT OF AGRICULTURE. 
wide and 2 rods long. On November 11, after the adult Hessian flies 
had ceased to fly, determinations of the percentage of fly infesta- 
tion were made in all the plats by W. B. Cartwright, of the Bureau 
of Entomology. In the early part of the following spriag observa- 
tions were made in the same plats by Dr. R. W. Webb, of the Bureau 
of Plant Industry, to determine the percentage of rosette infestation. 
The results of these observations of infestation are given in Table 1. 
Table 1. — Infestations of Harvest Queen wheat by the Hessian fly in the fall 
of 1920 and by rosette in the spring of 1921 on plats near Granite City, III. 
Date of sowing. 
Plants showing infesta- 
tion (per cent). 
Hessian fly, 1 Rosette, in 
in the fall, the spring. 
2.5 


93.6 
85.6 
October 11 
96.0 
Since rosette develops very early in the spring, before the spring 
emergence of the Hessian fly adults, it is obvious that any possible 
connection between this insect and rosette can involve only the fall 
infestation of the Hessian fly. It will be noted from Table 1 that 
there is no direct correlation between the percentage of fall Hessian 
fly infestation in any of the plats and the percentage of rosette in 
the same plats the following spring. The fall fly infestation was in- 
significant or absent, while the percentages of rosette were very high. 
It is therefore quite evident that some other factor than the Hessian 
fly is the prime cause of wheat rosette. 
While all evidence indicates that the disease in question is not 
caused by an insect, particularly the Hessian fly, it is recognized that 
under certain conditions there is a possibility of confusing the symp- 
toms of the disease with certain of those produced by the Hessian 
fly, the wheat strawworm (Harmolita grandis Riley), and to a less 
extent the wheat stem maggot (Meromyza americana Fitch). It 
therefore seems advisable to give the chief points of similarity and 
difference between the symptoms of the maladies under discussion. 
The insects discussed in this paper have long been recognized as 
important wheat pests, and details of their respective life histories 
will not be included. Osborn (£), 2 Webster (5), and many others 
have recorded the life history of the Hessian fly. Phillips (3) has 
given similar information concerning the wheat strawworm, and 
Webster (4) has discussed the life history of the wheat stem maggot. 
SYMPTOMS OF WHEAT ROSETTE. 
A complete description of the symptoms of wheat rosette has been 
given by the senior writer in another publication (1). 
FALL PERIOD. 
Field symptoms. — As this disease is interpreted at the present 
time there are apparently no field symptoms in the fall. During 
the past two seasons a highly susceptible variety of wheat growing 
2 Serial numbers (italic) in parentheses refer to "Literature cited" on page 8 of this 
bulletin. 
