712 IOWA DEPARTMENT OF AGRICULTURE. 



with this pest is applicable in all cases. Among the more important meas- 

 ures to be recommended for actively combating the brown rat are: (1) 

 Poisons; (2) traps; (3) ferrets; (4) fumigation; and (5) rat-proof con- 

 struction of buildings. 



POISONING. 



Barium Carbonate. — One of the cheapest and most effective poisons for 

 rats and mice is barium carbonate, or barytes. This mineral has the 

 advantage of being without taste or smell; and, in the small quantities 

 used in poisoning rats and mice, is harmless to larger animals. Its action 

 on rodents is slow, but reasonably sure, and has the further advantage 

 that the animals before dying, if exit be possible, usually leave the prem- 

 ises in search of water. Its employment in houses, therefore, is rarely 

 followed by the annoying odor which attends the use of more violent 

 poisons. 



The poison may be fed in the form of a dough made of one-fifth barytes 

 and four-fifths meal, but a more convenient bait is ordinary oatmeal, with 

 about one-eighth of its bulk of barytes, mixed with water into a stiff 

 dough; or the barytes may be spread upon bread and butter or moistened 

 toast. The prepared bait should be placed in rat runs, a small quantity at 

 a place. If a single application of the poison fails to drive all rats from 

 the premises, it should be repeated with a change of bait. 



Strychnine. — Strychnine is a more virulent poison, but its action is so 

 rapid that the animals often die upon the premises, a circumstance which 

 prohibits its use in occupied dwellings. Elsewhere strychnine may be 

 employed with great success. Dry strychnine crystals may be inserted 

 in small pieces of raw meat, Vienna sausage, or toasted cheese, and these 

 placed in the rat runs; or oatmeal may be wet with a strychnine sirup, 

 and small quantities laid out in the same way. 



Strychnine sirup is prepared as follows: Dissolve a half ounce of 

 strychnia sulphate in a pint of boiling water; add a pint of thick sugar 

 sirup and stir thoroughly. A smaller quantity of the poison may be pre- 

 pared with a proportional quantity of water. In preparing the bait it is 

 necessary that all the oatmeal should be moistened with sirup. Wheat 

 is the most convenient alternative bait. It should be soaked over night 

 in the strychnine sirup. 



Other Poisons. — The two poisons most commonly used for rats and 

 mice are arsenic and phosphorus, nearly all commercial preparations con- 

 taining one or the other as a basis. While experiments prove that rats 

 have great powers of resistance to arsenic, it may sometimes be used 

 advantageously as an alternative poison. Preparations of phosphorus sold 

 by druggists are often too weak to be effective; and home-made mixtures, 

 when of sufficient strength, are dangerous, as rats may carry the baits into 

 walls or crannies and thus cause fires. For these and other reasons the 

 Biological Survey does not recommend preparations containing phos- 

 phorus. 



Poison in the Poultry House. — For poisoning rats in buildings and 

 yards occupied by poultry, the following method is recommended: Two 

 wooden boxes should be used, one considerably larger than the other, and 

 each having two or more holes in the sides large enough to admit rats. 

 The poisoned bait should be placed on the bottom and near the middle 



