14 



ward, has alreudy been explained. At present the Bureau of Ento- 

 mology is conducting- experiments in fall wheat sowing- in nine States, 

 covering- approximatel\" the country between latitude 33" and 46'. 

 Here wheat is being- sown every ten days during- Septeml)t>r. Octo- 

 ber, and November, year after year, with the expectation of determin- 

 ing the approximate date of safety for seeding in th(> fall to evade 

 attack of the fly. While these experiments have not ])een going on 

 for a long- enough ti nu^ to give results sufficiently definite, covering- 

 all variations in the weather during these months, it is safe to say that 

 wheat may probably be sown, without danger from Hessian fly attack, 

 in northern Michigan soon after the first of September; in southern 

 Michigan and northern Ohio, about September 20; in southern Ohio, 

 after the first week in October; in Kentuck}- and Tennessee, October 

 10 to 20; in Georgia and South Carolina, October 25 to November 15. 

 •So far these dates are onl}* approximate, and serve to show in a general 

 way about the time when the fall brood of the fly will have largely disap- 

 peared over the wheat belt east of the Mississippi River. As the 

 larger part of the fall brood appears and is gone within a week, it is 

 possible for a farmer to so time his seeding as to avoid it, and this is 

 by far the most practical and efi'cctive preventive measure that can be 

 applied. 



CKOl' ROTATION'. 



Aside from the general benefits to be derived from crop rotation, it 

 compels the Hessian fly, when it emerges from the stubble in the fall 

 (or spring in the Northwest) to travel a greater or less distance to 

 reach young wheat plants. 



If, during this season of migration, storms or heavy winds occur, 

 these frail creatures will be driven about or beaten down until a com- 

 paratively small number survive to reach their destination. On the 

 other hand, if they are not obliged to leave the field where the}' 

 emerge, this mortalit}- will be vastl}^ lessened. 



BURNING feTUBBLE. 



This is the most efficient measure of all. as fire will reach and 

 destroy not only the Hessian fly ))ut all other insects infesting the 

 stubble, including the joint-worm. Unfortunately, it can not be gen- 

 erally carried out. Over a large portion of the Middle ^^'est timothy 

 and clover are sown, either with the wheat or during late winter or 

 early spring, and therefoi'e stu))ble-g-round can not l)e burned over. 

 Fields not followed by grass or clover can usually be burned over if 

 the grain is cut rather high at harvest and a mower is run over the 

 field and the mown grass, weeds, and stubble allowed to dry for a few 

 daj's just before the burning. This is nuudi the more feasible measure 

 in the Northwest, and ou"-ht to be more creneralh- followed. 



