June, ’23 
PARKER: HESSIAN FLY 
301 
locally and have been used to good advantage in the fall seeding cam¬ 
paigns. At the present time the few early sowed fields that we can 
find scattered over these counties furnish the only evidence of what 
would have happened had the wheat been sown at the time formerly 
practiced. These fields stand as testimony that the job was well done 
and that the control that was brought about was due to cooperative 
effort of the farmers and not by natural agencies. 
The hessian fly control in northern Ohio has been difficult because of 
the following reasons.: 
1— Farmers had been used to seeding wheat during the middle of 
September. 
2— The fly-free dates as they occurred varied considerably through¬ 
out four of the five years. They were as follows: 
1918— Sept 18th in northern counties to Oct 4th at Ohio River 
1919— Sept 28th “ “ “ “ “ 3rd “ “ 
1920— Oct 10th “ “ “ “ “ 6th “ 
1921— Sept 22nd “ “ “ “ “ 4th “ 
1922— Sept 23rd “ “ “ “ “ 2nd “ 
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The record of field infestation as it occurred during the five years in 
the counties in northwestern Ohio including or adjacent to the site of the 
* 
two emergence stations is shown in the tables. Where two or more fields 
of the same seeding date were examined the average infestation for all 
is given. 
Hessian Fly Fall Infestation Determined by Examination of Approximately 100 Plants in 
Each Field 
Erie and Sandusky Counties 
Williams County. 
When Sowed 
Percent Infested 
When 
Sowed 
Percent Infested 
Sept 10 
24% 
Sept 
3 
12% 
11 
34% 
10 
1% 
12 
34% 
17 
0% 
13 
38% 
20 
0% 
14 
17% 
15 
15% 
18 
8% 
20 
2% 
21 
0% 
* 
22 
0% 
25 
1% 
28 
0% 
1919 
Sept 22 
58% 
Sept 
6 
90-100% 
23 
63% 
12 
70-80% 
24 
47% 
17 
30-50% 
25 
38% 
18 
30-50% 
26 
41% 
20 
20-30% 
27 
6% 
22 
10-20% 
29 
1% 
24 
10% 
30 
0% 
1920 
25 
0% 
Sept 15 
79% 
Sept 
15 
52% 
17 
80% 
16 
41% 
23 
100% 
17 
47% 
27 
35% 
18 
30% 
29 
32% 
19 
36% 
