﻿98 BULLETIIsr 1369, U. S. DEPARTMENT OF AGRICULTURE 



jected into the cysts; derris used in dry form, as an ointment with 

 petrolatum, or in suspension in water when injected into the cysts, 

 or applied as a wash {111) ; iodoform and petrolatum, also pyre- 

 thrum and petrolatum, when applied as an ointment; and very fine 

 tobacco dust and nicotine dust used in powder form. 



The results of the writers' work seem to indicate rather clearly 

 that the percentage of mortality is not so high in the case of H. hovis 

 as with H. lineaturti. 



The treatment of cattle in practice requires the application of a 

 method which will be as effective as possible under adverse con- 

 ditions. When treatments are given by the livestock owners them- 

 selves, washes applied to the entire back of the animal are probably 

 the most dependable, in that the inexperienced operator is more 

 likely to treat all of the grubs than if the latter have to be found 

 individually. On the other hand, there may be some objection to 

 the use of washes on the entire back of the animal under certain 

 adverse weather conditions. An objection to the use of the syringe 

 is that the instrument is an item of expense and may be broken even 

 if carefully handled. This tends to commend the oil can if the 

 grubs are to be injected individuall3^ In the writers' experience 

 they have found that an oil can with a comparatively slender curved 

 point is the most convenient to use. If the aperture in the spout 

 is not too large the spout can be utilized to advantage in finding the 

 grub hole. One advantage in the use of an ointment such as iodo- 

 form -petrolatum is that the operator can easily recognize which 

 grubs have been treated. The use of powders is favored by those 

 who do not wish to wet the animals during the winter, but some 

 objection might be had to them on account of the possibility of the 

 dust getting into the buckets during milking. With certain washes, 

 however, the dust is left in the hair after the animal has dried. A 

 careful application of dust to the backs of cattle is almost as certain 

 to reach all grubs as the use of a wash. 



Tobacco infusion has been advocated for the destruction of grubs 

 in the backs of cattle by Carpenter, Phibbs, and Slattery {19). 

 Although results of the writers' preliminary tests with similar infu- 

 sions were not satisfactory, they continued their experiments after 

 receiving Carpenter's favorable reports. In his early publications 

 he gave no idea of the strength of the decoctions he used, and it ap- 

 pears that he must have employed infusions with a higher percentage 

 of nicotine than the writers were able to obtain from American to- 

 bacco dusts by using his formula. When, however, tobacco dust 

 from the same source as that employed by Carpenter (see Table 11, 

 tobacco infusion No. 2) was used, the mortality obtained (65.38 per 

 cent) was not nearly so high as reported by Carpenter. With most 

 of American tobacco dusts, which run from 1 to 1% per cent nico- 

 tine, great difficulty was found in obtaining an infusion containing 

 0,5 per cent of nicotine. In order to get such a percentage the 

 amount of tobacco dust advised in Carpenter's formula was doubled, 

 being 8 pounds of tobacco dust, 4 pounds of stone lime, and 1 gal- 

 lon of water. In preparing this the lime was first slaked in the 

 water, and then the tobacco dust was stirred in and allowed to stand 

 about 24 hours. The mass was then placed in a sack and pressure 



