6 BULLETIN 888, U. S. DEPARTMENT OF AGRICULTURE. 



Powdered pyrethrum stems were carefully tested and proved to be 

 of no value against these insects. 



TOBACCO POWDERS. 



A series of 27 tobacco powders ranging from 0.025 to 5.26 per cent 

 nicotine was thoroughly tested against chicken lice and the results 

 of these tests may be summarized briefly as follows: From 0.75 to 1 

 per cent of nicotine is of some value against these lice, but 1.15 or 

 1.25 per cent is as low as can be relied on for the best results, and even 

 then the powder must be very freely and carefully applied. 



NAPHTHALENE. 



A large amount of work has been done with naphthalene in various 

 forms as a remedy against chicken lice. 4 The data gathered show 

 that powders containing 20 per cent or more are Very effective but can 

 not be generally recommended, since as little naphthalene as 10 per 

 cent may temporarily injure the dusted fowls and 60 per cent may 

 kill them if the powder is well rubbed in. 



Finely powdered naphthalene was found to kill from 20 to 100 per 

 cent of the lice when sifted over the backs of fowls after they had 

 gone to roost at night. While in no case were the lice completely 

 eradicated by this treatment, and it is not as effective as the dusting 

 of the individual birds, it is considered that this method may be of 

 some value. 



Numerous tests with naphthalene (6.49 to 100 percent) nest eggs, 

 which have been frequently sold as remedies for lice on laving and 

 sitting hens, proved that they were of absolute^ no value. When 

 these eggs were placed in nests used by laying hens and allowed to 

 remain from 1 to 3 J weeks, no effect could be noted on the lice and in 

 several cases they were more abundant at the close of the experiment 

 than at the beginning. They were useless against lice on sitting 

 hens either when placed under the hen for two hours each week (as 

 recommended), or when allowed to remain under the hen for the 

 entire incubation period. Under the latter conditions, especially 

 during hot weather, the hens were frequently driven from the nest 

 and some of them were made very sick for two or three days. There 

 was also considerable evidence to show that the eggs were seriously 

 injured by the naphthalene, but not enough data are available to 

 prove this absolutely. 



MISCELLANEOUS POWDERED SUBSTANCES. 



The following is a list of powdered substances that were'found to 

 be effective against chicken lice when used as dusts: Arsenic trioxid, 

 barium fluorid, barium tetrasulphid, 5 borax, boric acid, cloves, naph- 



< Abbott, W.S. Naphthalene v. Chicken lice. In Jour. Econ. Ent., v. 12, no. 5, p. 397-402. 1919. 

 & Did not kill all the lice. 



