June, ’23 
mccolloch: hessian fly, resistant wheat 
293 
about the same time. The flies emerge by pushing off the lid at one end 
of the cocoon, the lid whose separation from the cocoon allows the es¬ 
cape of the adult moth. 
Judgingfrom reports and my own observations, this Tachinid is quite 
an effective enemy of the Oriental moth and it would be well worth 
importing and establishing, particularly in view of the increase of its 
host the last two years. 
At the close of this paper, the final business was transacted, which is 
given in the report of the business session. 
THE RESISTANCE OF WHEAT TO THE HESSIAN FLY—A 
PROGRESS REPORT 1 
By J. W. McColloch, Associate Entomologist, and S. C. Salmon, Professor of Farm 
Crops, Kansas Agricultural Experiment Station 
Abstract 
The study of the resistance of different varieties of wheat to the Hessian fly, 
Phytophaga destructor Say, has been under way for several years. The results dis¬ 
cussed in the present paper show that resistance does occur in the field and that this 
resistance is fairly constant. Soft wheats, as a class, are more resistant than hard 
wheats. The cause of resistance has not been determined, but many factors have 
been eliminated. The evidence indicates that it is due to physiological causes and 
that silica is in some way associated with it. 
In a previous paper, 2 the writers presented a preliminary report on the 
relation of small grains to Hessian fly (.Phytophaga destructor Say) injury, 
in which it was pointed out that the fly is able to discriminate between 
wheat, rye, barley and oats in ovipositing, and that there is a marked 
difference in the infestation of these grains and in the different varieties 
of wheat. In other words, certain kinds of small grains and certain 
varieties of wheat were resistant to the Hessian fly. The investigations 
have been continued whenever sufficient fly has been present and a large 
Contribution from the Department of Entomology, No. 84, and from the De¬ 
partment of Agronomy, No. 142, cooperating. This paper embodies some of the 
results obtained in the prosecution of projects Nos. 8 and 67 of the Kansas Agricultural 
Experiment Station. The writers desire to express their appreciation of the as¬ 
sistance rendered by Mr. J. H. Parker, Plant Geneticist, in the selection and propa¬ 
gation of certain of the plants, and to Messrs. H. Yuasa, M. G. Stahl, and F. C. Lewis 
for carrying out certain phases of the work. 
2 McColloch, J. W., and Salmon, S. C. Relations of Kinds and Varieties of 
Grain to Hessian Fly Injury. In Journ. Agri. Research 12:519-527, 1918. 
