Cattle-Fever Ticks. 19 



are longer. Cotton ^ obtained at Knoxville, Tenn., during the years 

 from 1907 to 1909, inclusive, the periods given in the lower part of 

 Table 1. 



According to the experiments conducted by Cotton, the normal 

 duration of an infestation may be considerably shortened or even 

 suddenly brought to an end in infested pastures and fields by the 

 occurrence of exceptionally cold weather. He found that a certain 

 per cent of engorged females are destroyed by a temperature of 

 23° F., that all engorged females are destroyed by a temperature of 

 14° F. when not provided with a protective covering, and that ticks 

 provided with a covering of dry chaff were able to survive a tem- 

 perature of 12° F., but if the covering is wet they are killed as 

 readily as when unprotected. It was found also that ticks that have 

 deposited some eggs are much more readily destroyed than those 

 that have not done so. In addition it was demonstrated that all 

 unprotected eggs and all seed ticks are destroyed at temperatures 

 of 4° F. and 2° F., respectively, but that eggs protected by dry litter 

 can endure a much colder temperature. It is thus seen that the in- 

 festation of fields may be greatly reduced during cold spells and, if 

 the temperature falls to about zero, may be entirely destroyed. In 

 case the temperature falls only to a point at which all the females 

 are destroyed, the only result accomplished will be a shortening of 

 the period of infestation. 



It would be well for stock owners, in eradicating ticks, to take 

 advantage, so far as practicable, of all zero weather. It should be re- 

 membered, however, that cattle even during the coldest weather are 

 likely to harbor ticks which will be unaffected by the low tempera- 

 ture. The ticks when they drop will reinf est the place ; consequently, 

 when a spell of zero, weather occurs, if the cattle are not on the fields, 

 pastures, or ranges they should not be returned to them until freed 

 of ticks. If on pasture they should be removed at once and not re- 

 turned until made free of ticks bj^ one of the methods suggested in 

 this bulletin. 



TIME REQUIRED TO FREE CATTLE OF TICKS ON UNINFESTED FIELDS. 



Although the method is not often used, it is nevertheless possible 

 to free cattle of ticks by placing them on a series of uninfested fields. 

 This plan is based on the fact that the female tick must drop from 

 the host to the ground before eggs can be laid and before young ticks 

 will develop. 



The shortest time in which seed ticks 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 



1 Bulletin 94, Agricultural Experiment Station of the University of Tennessee. 



