494 



DISEASES OF CATTLE. 



nient, while those which fail to find a host will die in the pasture 

 from starvation. 



Animals may be freed of ticks in two ways. They may be treated with 

 an agent that will destroy all the ticks present, or they may be rotated 

 at proper intervals on tick-free fields until all the ticks have dropped. 



Time required to kill ticks hy starvati&ii. — The time required for 

 the ticks to die out after all animals have been removed from infested 

 fields and pastures varies considerably, depending principally on cli- 

 matic and weather conditions. The dates when pastures will be free 

 of ticks, beginning during each month of the year, are given in the 

 following table : 



Time required to free pastures from ticks by starvation. 



Date of removal of all animals 

 from pasture. 



Date when pas- 

 ture will be free 

 from ticks. 



Date of removal of all animals 

 from pasture. 



Date when pas- 

 ture will be free 

 from ticks. 



July I 



August 1 



September 1 



Octoljer 1 to November 1, inclusive 

 December 1 



March 1. 

 Mayl. 

 Julyl. 

 Augtist 1. 

 August 15. 



December 15 to March 15, inclusive. 



Aprill 



April 15 



May 1 to June 15, inclusive 



September 1. 

 September 15. 

 October 15. 

 November 1. 



The above table is based on investigations by Hunter and Hooker ^ 

 at Dallas, Tex., and by Graybill ^ at Auburn, Ala. All the periods 

 obtained by Newell and Dougherty (1906)^ in work carried on at 

 Baton Rouge, La., which is much farther south, are shorter. The 

 above periods should be found ample for all localities lying no far- 

 ther north than Dallas, Tex., or Auburn, Ala. The periods necessary 

 to starve out an infestation for many localities in the southern part of 

 the infested region are no doubt somewhat shorter than those given 

 above. In general, moisture and cold prolong and dryness and heat 

 shorten the duration of an infestation. If various portions of the 

 same pasture differ with regard to temperature and moisture, as is 

 frequently the case, some parts become free of ticks before others do. 

 Other things being equal, high, dry, unshaded land becomes tick 

 free sooner than low, damp, shady land. 



The simplest and safest plan in most cases, however, will be to 

 follow the foregoing table in the region indicated for it. It is prob- 

 able that the periods given in the table should be lengthened a little 

 for the northern part of the infested region. The experiments con- 

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

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



1 Bulletin 72, Bureau of Entomology, U. S. Department of Agriculture. 



2 Bulletin 130, Bureau of Animal Industry, U. S. Department of Agriculture. 

 ' Circular 10, State Crop Pest Commission of Louisiana. 



