REMEDIAL AND PREVENTIVE MEASURES. 137 



East Africa, states that it is with them the most effective measure at 

 their command for destroying the " green fly" in wheat fields. With 

 us it was used after the aphidid had fully established itself and was 

 literally swarming over the growing grain. Earlier, at the commence- 

 ment of an outbreak, the effect of its use might prove more satisfactory. 



Similar experiments were carried out with a heavy roller, such as is 

 generally used among farmers for crushing clods in fields and com- 

 pacting the ground. (See PI. IX, fig. 2). In this case the 'results 

 were even less satisfactory than with the brush drag, because the 

 roller acted only on the clods and other inequalities in the surface of 

 the ground. Where the wheat had been drilled the effect on the Tox- 

 optera was less decisive than where the grain had been sown broad- 

 cast. The wheat plants grow in the narrow furrows or grooves and 

 the insects that were displaced dropped down about the plants and 

 the passing roller struck only the ridges, leaving the insects practically 

 untouched. 



Where the invasion is not chiefly from outside the field itself, and 

 the pest makes its first appearance in spots, management is less 

 difficult. By plowing under these infested spots and immediately 

 harrowing and rolling them further damage may be effectually pre- 

 vented. The junior author had an opportunity to test this measure 

 in western Oklahoma. Covering these spots with straw, where easily 

 obtainable, and burning, is equally effective, but where this last 

 measure was applied by farmers in Oklahoma in 1907 the fields were 

 so completely overrun from the outside that the good effects were 

 entirely obliterated. 



As between these two methods of suppression, it must be borne in 

 mind that while the seriously affected spots in a field are very small, 

 a single load of straw will suffice to cover a number of them, prepara- 

 tory to burning, but after these areas become enlarged it is much more 

 practicable to plow them under. 



Besides the above-mentioned methods of control, experiments 

 were conducted with different kinds of spray materials. In all of 

 our control methods we endeavored to place ourselves in the position 

 of the farmer, and to use such apparatus as could be obtained locally. 

 Accordingly the junior author, upon reaching Hobart, Okla., the 

 first week in April, 1907, prepared to begin some spraying experi- 

 ments. The only spray apparatus that could be found in the town 

 was a knapsack pump. As stated above, since an outbreak of 

 Toxoptera starts in small areas, where the infestation originates 

 within the field, it was thought possible to accomplish something by 

 spraying these areas. As the infestation at Hobart seemed to be 

 quite general, apparently originating from migrations from farther 

 south and east, the small pump was found to be utterly useless. 

 From here the junior author proceeded to Kingfisher, Okla., where 

 there were clearly defined areas of infestation, and, together with 



