TEXAS FEVER. 



487 



the periods given in the table should be lengthened a little for the 

 northern part of the infested region. The experiments conducted 

 thus far in various places indicate this, and it will place the eradica- 

 tion work in that region on the safe side. For example, E. C. 

 Cotton^ obtained at Knoxville, Tenn., records for September and 

 April somewhat longer than those given above. They are as follows : 



Cattle removed April 15; pasture free of ticks November 13. 

 Cattle removed September 15 ; pasture free of ticks July IS. 



In localities with temperature and other conditions similar to those 

 at Knoxville, Tenn., these periods should l)e followed. 



Time required to render cattle free of ticks 'ichen placed on unin- 

 fested fields. — Before discussing plans for rendering farms tick free, 

 involving the use of the information given in the foregoing table, it 

 will be necessary to indicate how animals may be entirely freed from 

 ticks by placing them on uninfested fields. This is based on the fact 

 that the female tick must drop from the host to the groimd before 

 eggs can be laid and before young ticks will develop. 



The shortest time in which seed ticks Avill appear after engorged 

 females have been dropped is 20 days. Consequently cattle placed 

 on a tick-free field during the warmer part of the year are not in 

 danger of becoming infested again with yoimg ticks until 20 days 

 have elapsed. The time required for all the ticks to drop after cattle 

 have been placed on uninfested land varies with the temperature, 

 being much longer during the Avinter than during the summer. The 

 time required, beginning at various times of the 3'ear, is given in the 

 following table : 



Tune requirerJ for all ficl-s to ciroi) fro)>i cattle placed on tick-free land. 



When tickv cattle are pl!ice<1. oa 

 tick-free land during — 



All ticks will 

 have dropped 



August Six weeks. 



September Do. 



October ! Eight weeks. 



November j Nine weeks. 



January Ten weeks. 



February \ Seven weeks. 



M'hen ticky cattle are placed on 

 tick-free land during — 



i March. 

 I April.. 

 I May... 

 I June. . 

 i July... 



All ticks will 



have dropped 



in— 



Seven weeks. 

 Six weeks. 



Do. 



Do. 

 Fi\e weeks. 



Freeing cattle of ticks hy rotation on tick-free land. — The plan of 

 freeing cattle of ticks by rotating them from one lot or field to an- 

 other is as follows: Beginning at any time from Februar}'^ to Sep- 

 tember, inclusive, the cattle are removed from the tick-infested pas- 

 ture to a tick-free lot or field and kept there for not more than 20 

 days. During this time a considerable number of ticks will drop. 

 In order to prevent the cattle from becoming reinfested (by seed 



* Bulletin 81, AgricuUiiral Experiment Station of the University of Tennessee. 



