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JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 16 
September emergence and the fraction of the brood that held over in 
the old summer stubble. Thus in April the three groups arising from 
the previous summer’s flaxseeds had again united. By July 1921 con¬ 
siderable loss from the hessian fly had occurred over all of northwestern 
Ohio. This was due almost entirely to the “late wave” or abnormal 
October emergence of 1920. At Columbus, where eggs of the “late 
wave” flies had been removed during October from several hundred 
plants, we watched the progress of damage during the fall and winter 
and compared it with the uninfested plants from which the eggs had 
been removed. In this way proof was secured that in central Ohio the 
most of the damage to the 1921 crop was done in the fall rather than in 
the spring and summer, which was evidently due to the high mortality 
of eggs deposited during cold weather in April. We also learned that 
the mid-October emergence had cost the Ohio State University ap¬ 
proximately four bushels of wheat per acre on the experimental plats. 
This damage was much greater in northern counties where the brood of 
flies was heavier. Southern Ohio counties, by united effort, in 1920 
eliminated the hessian fly as a menace in that part of the state. North¬ 
western counties, which had experienced two years of abnormal late 
emergence and egg-laying, had not yet completed the job. During the 
fall of 1921 and again in 1922 a large group of northwestern counties 
chose Sepember 25th as their first safe seeding date. They were suc¬ 
cessful in preventing 99% of the wheat acreage being sown before that 
time. During both of these years the hessian fly emergence had been 
nearly normal and egg-laying was over in time to make this date safe. 
Climatic conditions were also favorable for the growth of late sowed 
wheat. The result has been that northwestern Ohio has at last won their 
victory and has the hessian fly well under control. 
Commencing with the fall of 1920 the Ohio State University and State 
Experiment Station have each year conducted field emergence stations 
in two widely separated counties in northwestern Ohio. The manner of 
conducting these stations has been described in a previous publication. 1 
This paper has to do mainly with the follow-up records of the percentages 
of plant infestation during November and their relation to the time of 
sowing. We have resorted to the gathering of much local data in these 
counties as a basis for future recommendations. These percentages of 
plant infestation were taken from experimental sowing plats and from 
a large number of fields scattered over these counties. The correct seed¬ 
ing dates of fields were in many cases recorded by the township crops 
committeeman. The results of the field inspections have been published 
flournal of Economic Entomology, Vol. 14, No. 1, 1921. 
