February, '21] gossard and parks: hessian fly prevention 55 



those which had been generally accepted by our entomologists and 

 agriculturists as safe in previous years. 



Result of the Late-Sowing Campaign of 1919 



In the northern counties, probably nearly fighty percent, of the 

 growers waited for the suggested dates before sowing. In the central 

 and southern counties, about ninety percent, of the growers in counties 

 having farm bureaus waited for the proper dates. The wisdom of this 

 was seen in November, b\^ which time the early sowed wheat all over 

 Ohio had been destroyed by a verj- heavy fall brood of fly. Those who 

 sowed before the dates suggested, everywhere suffered heavy and some- 

 times total loss. This is well illustrated by the yields obtained from the 

 "date of sowing" plats on the Miami County Experiment Farm, which 

 are here given : 



Percent, of plants Yield in 



When Sowed infested Nov. 1919 July 1920 



Sept. 8 100 16..T bu. 



Sept .16 100 18.5 



Sept. 23 100 12.5 



Sept. 27 55 27.0 



Sept. 29 10 37.4 



Oct. 2 40.0 



Oct. 4 •. 37.8 



Oct. 13 36.1 



Oct. 20 21.6 



The seeding dates proved generally trustworthy for southern Ohio 

 but not for northern, where wheat was damaged if sown as late as Septem- 

 ber 26, or eight days later than recommended. By November, it was 

 determined that there was a range of only five days in the departure 

 of the fall brood from Lake Erie on the north to Cincinnati on the 

 south, instead of 14 days, as should be the case, if it had obeyed the law 

 of latitude. In southern Ohio less than 10 percent, of the wheat became 

 infested, but 80 percent, is our estimate for several northern counties. 



Preliminary Work of 1920 



During July, 44 counties were visited by the surveyors and the 

 distribution of the spring and summer damage was found to conform to 

 the previous fall infestation. The area of greatest density of infestation 

 had moved from north-central to north-western Ohio. In one county, 

 eighty-nine percent of all straws had been killed or damaged by the fly. 

 On many of the best farms in northern Ohio the average wheat yield 

 was not over eight bushels per acre, where in other years yields of 35 

 bushels had frequently been obtained. Many wheat fields were cut for 

 timothy. 



The survey showed that 44 percent, of all straws examined in the 

 state were either killed or damaged by fly. Material was collected in 



