250 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 10 



"follow up" work to learn the results of individual attempts to control 

 the insect. 



In 1916 there was early observed in this county a great difference in 

 the degree of injury caused by the spring brood of the Hessian fly. The 

 grain in some fields suffered but little while in other fields it was ruined 

 by the fly. Frequently the most seriously injured grain had been sown 

 after the fly-free date. This fact the farmers were always sure to re- 

 member and especially if, as occasionally happened, a neighboring field 

 which was sowed before the fly-free date had escaped with less injury. 



To explain these differences, as well as to secure some definite data 

 on the value of an unorganized effort to control the Hessian fly, a ques- 

 tionnaire was prepared, and 306 fields in this county were visited and 

 the owners consulted. Among the questions asked these growers 

 were the following : 



1. When was the field sowed? 



2. Was volunteer wheat present in the seed-bed at seeding time? 

 None, medium or much? 



3. Did early sown wheat join? 



4. What crops occupied the field in 1914 and 1915? 



5. Was any stubble burned in 1915? 



It was desired to determine the answers to the following questions 

 pertaining to the control of the Hessian fly over an entire county: 



1. What per cent of McPherson county wheat-growers beheved in 

 and had waited until the fly-free date for their county to sow wheat in 

 1915? 



2. How much protection was afforded the 1916 crop by sowing after 

 the fly-free date without regard to the amount of volunteer wheat present 

 in the seed-bed? 



3. What effect did the presence of different amounts of volunteer 

 wheat at seeding time, in fields sown after the fly-free date, have upon 

 the injury done by the spring brood of 1916? 



These fields were visited usually in company with the farmer and the 

 wheat carefully examined for injury by Hessian fly. Account was 

 taken of the presence of lodged straws, dead tillers and number of flax 

 seeds found present in representative samples taken in different parts 

 of the field. The infestation was then classified as slight, medium or 

 heavy, as the case might be, and so tabulated together with the other 

 records given by the farmer. No data on the 1916 yields were ob- 

 tained as this survey was conducted during July, and factors other 

 than Hessian fly contributed to make the yields variable. 



This work was made possible in the Hmited time available through 

 the assistance of R. R. Reppert of the Department of Entomology, 



