of different components being alike as judged 
by final results. 
Value of Resistance: The resistance of wheat 
varieties to the Hessian fly is a long-time il- 
lustration of the value of such varieties. 
In Kansas from 1871, when it reached the 
eastern counties, until the late 1930's and 
1940's, when resistant varieties provided the 
needed control, the Hessian fly caused yearly 
losses from $5 million to $25 million in out- 
break years. Kawvale, approved in 1932 in 
Kansas, was the first Hessian fly-resistant 
wheat variety released by an experiment sta- 
tion and recommended for growing byfarmers 
in a State. It reached a maximum of over one- 
half million acres in Kansas about 1939 (Clark 
and Quisenberry, 1948) (table 3). Pawnee was 
released to Kansas farmers in 1943 because 
it was superior to Kawvale in several agro- 
nomic and milling quality characters. By 1951, 
it had reached its maximum acreage in Kansas 
of nearly 7 million acres, including more than 
90 percent of the wheat acreage in 27 counties. 
Principal acreage was in the eastern half of 
Kansas, where the Hessian fly had been com- 
monly injurious. For this area also the highly 
fly-resistant variety Ponca was approved for 
farmer use in 1951, and reached a maximum 
Kansas acreage of 1,787,500 in 1959. Mean- 
while, the resistant varieties had a disastrous 
effect on the Hessian fly population in the 
eastern half of Kansas, despite all counties 
still having some susceptible varieties (fig. 3). 
Furthermore, the leading resistant variety, 
Pawnee, carried at best only about 50 percent 
resistance. A new Hessian fly-resistant 
variety, Ottawa, was released in 1960 and 
reached a Kansas acreage of about 800,000 
by 1964, It is still increasing in acreage. 
Meanwhile, in 1958 a severe outbreak of 
wheat streak mosiac occurred in north-central 
Kansas, All Hessian fly-resistant wheat 
varieties are susceptible to that mosaic, but 
some Hessian fly-susceptible wheats carry 
some tolerance to the disease. Those varieties 
increased in acreage at the expense of Hessian 
fly-resistant ones. There has not been time 
enough between the first widespread outbreak 
of wheat streak mosaic in 1950 and 1958 to 
find tolerance to it and combine the tolerance 
with fly resistance. Hybrids with both char- 
acters are now in yield nurseries. The effect 
on the fly population of the decreasing acreage 
of resistant varieties was quickly evident 
(table 4). 
The Fort Hays Branch Experiment Station 
was in the area of heavy infestation and af- 
forded new evidence of the effectiveness of the 
resistant varieties. It also afforded an op- 
portunity to compare the variety Turkey, which 
was commonly grown in Kansas when work 
begain on Hessian fly resistance in 1914, with 
recently fly-resistant varieties (fig. 4). A re- 
turn to the use of more resistant varieties 
over the areain 1963 and 1964 was accompanied 
by a short drought that further reduced the fly 
population. A review of the history (table 4) 
of the use of these resistant wheat varieties 
shows that it has been necessary to replace 
older resistant varieties with new ones asnew 
varieties improved, for other characters be- 
come available. 
The Hessian fly has always been considered 
highly destructive (Hyslop, 1938; Brown, 1964). 
It ranked ninth among the 49 individual in- 
sects for which estimates of damage were made 
by Hyslop. In Kansas from 1923 to 1927, the 
estimated average annual loss was 18,500,000 
bushels, or 15 percent of the crop; and from 
1926 to 1935, the estimated annual loss was 
5,731,000 bushels worth $4,033,000 (depression 
dollars) (Hyslop, 1938). During 1947-60 in 
Table 3.--History of Kansas Hessian fly-resistant wheat varieties. From Kansas 
(State Bd. Agr. Div. Statistics reports) 








Year 
Variety distributed 
ee 
DIO OOS0'O"0, DOr 
Kansas maximum 
acreage and year 

500,000 
6,663,830 
1,787,533 
872,562 

Remarks 








(1939) Now replaced by Pawnee. 
(1951) Kawvale resistance. 
(1959) Marquillo and Kawvale resistance. 
(1964) Ill. No. 1 resistance. 


