Historic, archived document

Do not assume content reflects current
scientific knowledge, policies, or practices.

_UNITE: 6TATES DEPARTMENT OF THE INTERIOR
a » ISH AND WILDLIFE SERVICE

ge ;
ae WASHINGTON 25, D. C.
g2 en \
Vie ayat § Leaflet WL - 337
‘ = ae) January 1952
» ea
a Bocuse OF COMMON RODENTICIDES

Research and experience, over the years, have thus far failed to produce a rat
poison that is universally effective, one that meets all requirements under all conditions.
A number are quite useful; most have one shortcoming or another. A rodent-control
investigator or operator finds it necessary to be familiar with the characteristics of all
useful poisons in order to select the one - or series - that best fits each particular
circumstance. Such factors as toxicity, dosage levels, and relative effectiveness are
obviously important. Less often considered, but of equal importance, are degrees of
acceptance and reacceptance and the development of tolerances. Odor and taste may be
considerations in some instances. Solubility of the material has a definite bearing on
bait mixing techniques. Safety precautions are an essential part of any procedure,
requiring attention to hazards to the user as well as to humans and animals that might
come into contact with exposed baits. The appended table is an attempt to classify the
common rodenticides so that they can easily be compared for these purposes.

It is obvious that full justice cannot be given to some of the categories in the
abbreviated space allowed in the tabulation; many do not lend themselves readily to one
word descriptions. Although an effort was made to qualify noteworthy variations with
footnotes, minute and technical differences had to be sacrificed for the sake of brevity.
For example, the degree of hazard existing when a poison is used is purely empirical
unless it can be assumed that normal precautions will be followed. The term "antidote"
actually means the counteracting of an effect, whereas most so-called antidotes of
economic poisons are in reality first-aid treatments, followed by palliatives and sedatives.
The statements listed in that column are simply abbreviated descriptions and are not
intended as complete directions. The differences between solutions and suspensions and
between different types of oils have led to a simple listing of whichever material serves a
useful purpose in bait mixing; even then some qualifications are necessary and occasional
variations in technique have to be ignored.

Not all animals react alike. Even within the same species some individuals are
considerably more resistant to toxic effects than the average. Some effects vary with
seasons, age classes, diet, and even with sexes. Dosage levels are usually calculated
to include the bulk of the above-average resistant animals. It is essential to understand
that no value accrues from increasing those levels. Such practice is doubly objectionable,
for acceptance is usually decreased while the hazard to other larger animals is greatly
increased. All that is accomplished is doubling the cost of the bait. Continued re-use of
the same poison in the same location, except as noted below, generally results in a decline
in acceptance, bait shyness, and poor control. Poisons highly effective in one place are
sometimes less effective in adjacent properties. A thorough knowledge of the materials
available will assist in overcoming these problems.

avJONaWWooad diov 9ILAOV ONY TOHOOIY TAHLG YO NILAOVONOW | a “Sivu O41 SB VNONL9OSraGO ANN

————

ATALVIGAWWI NVIDISAHd V VIVO SAVMIV 'AAILO3443 ATIVOSN SI YaLVM WHYM 4O SSv70 v NI ‘(OWOlaBNOM. BBNOR “ono ‘wwae ic
Lvs JO 1N4NOOdS31A8VL | “IVILNASS3 SI G3adS ‘G3LON SV 1d39X3 Giv LSYI4 SV G|SN auv SOILAW3 11 COW > ‘LV AVMYON 1S1¥LOL 3OVM3AV) SHOW HO SAVG OI-s HO4 GauINDAU OW 1 40 SaS0a 3A‘SS300NS ©
‘Y3GMOd 3SOO7 ONIMVHNI JO YSONVG OS IV ‘NIMS 3H1 NI SHV3N9 YO SLND HOMOMHL NAXVL 3B NVO‘o1 “SLINS3Y 31138 3AIO GNV 3IBVIIVAY auV STIINDS 91xXOL 3HOW3A31 318V1d399V WNWININ &
“"3181SSOd ONINOSIOd SINOYHO 6 ‘SLOJYIG 1387 Sv 3SN‘WHO4 31Svd NI %E-1 WON4 AYA SNOILvHvdau¥d IWION3WWOO'e
‘BAISSHOV Nv SV G3SN 38 AVW 3LSVd HONVIS 8 ‘9W009 SV HOIH SY 1S3L SHIGMOd ASHVOD 3WOS ‘AVA S3GVHD dSN 4O S3ZIS 31IDILuVd z
‘NOISNAdSNS YO NOILNIOS YaLVM Vv SV G3SOdXx3 3a OST AVW Zz ‘ANNSOdX3 LSHI4 NO ‘KINO SLVY AVMYON 1
ONILOV 1SVJ AY3A @m@e JOIN 3SNOH GNV ‘SLVY 400Y ‘SLVY AVMYON ISNIVOV 3AI193453 eee
ONILOV 1SVj we AINO J0IN @e0e3e SLVY 4OO¥ GNV SLVY AVMHON LSNIVOV 3AI1L03443 ee
ONILOV MOS @ SLVY AVMYON ISNIVOV JAIL03443 @
SNYOHdSOHd SV AWS /31VYSGON SNYOHdSOHd SV AWVS) SFA ON ON OSNOYULS| SNOULS|/ONOYULS| ON ON goo9s | doo9 3QIHdSOHd ONIZ
ae eee
SNOISN4SNVUYL
goo1@ JIOHM) LHOIIS SA | ‘SOVHYYOWSH TWNY3LNI] SAA ON} SIA ANON | LHOITS|} ANON qoo9 | dood NIYVSYUM
GNV ‘XY NIWWLIA ‘LNVINDVOO-ILNY
oe eee
oe 128
a30Naw BYuNTivs AYOLY Snes
-WOO3Y 3LVIINSOIHL -UldS3Y ‘S9VWVG JNINOOd
wniaos anv 3aiaoi| SNSYLX3 -N3 NV AaNGIx ‘govHyHo| BON |,SAA|} ON} ANON | LHOIIS|) ANON aoo9 | aoo09 WAITIWHL
WNIGOS ‘378vI7134 “mn we W3H TWNILSALNI-OuLSV9 ose
3LV4I1NS
oa 3LVYSGOW oa
gON SAA ON ANON gINOULS ANON YO00d YyIv4 JNINHOAMLS
sen ecee
woow Yuva VIXAHdSV ‘NOILSNVH ontaaee
NI d33y ‘3A 1LVaaS ONV -X3 ‘W3LSAS SNOAY3N : al v
USLVM NI TvOouvHO ‘sain| JLVYSGOW 4O NOILWINWILS-uadns| @ON ANON |,9NOULS| ANON 400d ulv4 9°0 9 SNINHOAYLS
-NIW Ol Y3L4V O1L3N3 ON pow 3NG SNOISINANCS ORO
W31SAS ‘$8192/°Z0 | 3OIW=O1 (0801 GNNOdWODd)
zi4dNON | 3W3YL XS SNOAYAN IWYLN39 GNV| ON LH9INTS |} LHOITS| ANON qoo9 |} agoo9 ‘ya /'20 2h 4O0U=o 31Lvia90vo0uNONTs
pe LYV3H JO SISATWHVd MWMYON=G'| oo Wwnidos
ONILINOA 4O
SISATVYVd LYV3H
aavdvo SIvWINY OL] LHOITS i S3A SJA | 31v¥300W| ,ONOULS| 31V4300N 4yoO0d | ulv4 Ol} ,OOS enaueee
aN RIND. Ge onan eloy ayI1-SItvLI910 Li
+ —+ — -
OMI Sv) S710 aN 30vwva | mOATan
SLV4 GIOAV ‘Y3LVM a é
ONV OILYVHLVO folLawa|2LVYaGOW ONV gee aN SO BLSue SHA ON | SNOULS| SNOYLS/ONOYULS Y¥IV4 qoo9 GO Pye | “SnyYOHdSOHd
34043a 3Lv4IINS Y3dd09 ae «= OSA Tad LuvaH ee
W3LSAS SNOAY3N
< TWYLN3O JO SISATVUVd
ALV4INS WNISANOWW | LHOITS NOMOUBas aeeialisiale ON ptH9ITS | ANON 400d | ¥OOd O2| +OGZ | alvNoguvo wniuve
ew ‘SWSvdS IWNILS3LNI e =
i | (Q3ZINOYDIN)
oa ALVYSGOW] oON | ON oa ON |,S3A | ON | ANON |,3iv¥3acoW) 3NON | S3A | ON | Ulv4 | UlV4 S'| G2 3aIxo SNOINaSYY
: {oe s Oe 65 ; j Y E: Sol eae. 0 lee
NOM! 40 3alxo aaLoad4v Wal %
'u3LvM aNV ‘TIW|3LVYSIGOW] ON on {7848 BARMAN AvHANAS ON |,S3A] ON | ANON |93ivy3c0W] 3NON | S3A| ON | Ulva | YIVS g 2001 JQIXOINL SINSSYV
‘VISANOVW 4O TIN a ‘NO|LONYLS3q A3NGIy | L a eo
(SONNT SHL NI aints (VAYNOIHLTAHLdYNVHd7¥)
ANON |31VY30dOW) ON ON dO NOILONGOYd-43A0)| ON ON | S3A] LHOINS {31vy3G0OW] LHOITS| S3A | ON | YOOd | GQ09/| ,G009 Gal 8 NLNV
NoISn443 WWunad
a e
Sera DO. ao = eal | wi40 Srl |aolsel mo Tome: - |
Seam 92 | oe asva|asva| aug; EMT] oS Bie [S'S | Sel Beet 1S cen earns Gea ee ae
cpwm| v2 ° = = ° a ° moi eco Zo 2a
SALOGILNY axnm| 4 Size (Hivsa soyasnvo) lee Cu HAEYM SEN lio Suey Ge te ee S| co ml eam lester m gb
le sal lec tel ess pie m OFS [> p> im, || aemlicc ss w= xls SNOSIOd
o|}z 34 > v i U > m SEa= 2
Oo} 21/42 NOILOV af 2: || po ata ey = - 9
a | 4 ONIXIN LIVE 3 nia. Ole Oo |(ScOnl mes dec °
STVWINY YFHLO OL NI aasn uaiauvo| = 2 eee eo Glare ell aren o 8
GNV SNVWNH O1 NOILV134 27 c 2 °

SAGIOILNAGOY NOWWOO 3HL 4O SOILSIYSALOVYVHO SWOS

Warfarin, red squill, zinc phosphide, and ANTU are generally recommended for
use by the public. They are usually available commercially and are the ones with which
the untrained individual is the least likely to experience difficulties. Commercial
preparations of prepared baits containing arsenic, phosphorus, and strychnine are
commonly sold on the retail market; their use is best restricted to indoor protected
stations where accidental poisoning hazards are minimized. Barium carbonate, once
rather widely recommended, is rarely used today as it is too weak to be effective.
Thallium sulfate is very dangerous and quite costly; except for some grain-treated
baits used for mouse control, it is used almost exclusively by professional operators.
Sodium fluoroacetate, or Compound 1080, is not available to the general public because ©

of its extreme toxicity.

Of the first four materials mentioned above, red squill is considered among the least
hazardous poisons for the untrained individual to handle. Its emetic factor offers
protection to animals capable of vomiting. However, since some farm animals do not
vomit, care must be taken to prevent their contact with the material. Red squillisa
relatively distasteful mild poison, hence its shortcoming; so much must be incorporated
into the bait that some rats object to the taste and soon learn to refuse it. ANTU, if used
properly, will give good results against Norway rats, but is ineffective against roof rats
and, like squill, is of no value against house mice. The strong reluctance of rats to
accept a second dose as well as the marked tolerance which is developed have combined
with the accidental hazards to reduce sharply the use of ANTU throughout the country.

It should not be used more often than at four month intervals to obtain best results and
baits containing the material should not be left in place for more than three or four days.

Zinc phosphide is not widely used, partly because it is not readily available and
partly because of its high toxicity and strong odor. However, this offensive odor and
unattractive color provide a safety factor. Most domestic animals will not touch baits
prepared with it, but rodents seem to like the pungent odor of phosphorus compounds.
Furthermore, all species of rats and mice, both domestic and native, readily accept
zinc phosphide treated baits. The net result is that of the three poisons thus far
mentioned, it is the most likely to produce universally satisfactory results.

A greater degree of protection to other animals, when either zinc phosphide or
ANTU is used, may be obtained by incorporating tartar emetic (antimony and potasium
tartrate) in the bait mixture. Approximately equal amounts with ANTU or three parts
of tartar emetic to eight parts of zinc phosphide provide about the same relative degree
of protection to other animals as may be expected in the case of red squill.

Warfarin, outstanding in its value to the general public, is the most recent material
to be added to the list. It incorporates a radically different principle of control by poisons.
An anti-coagulant, this chemical must be taken daily over a period of several days as
opposed to the single dose compounds, The animals, apparently not associating the
cumulative effect of internal hemorrhaging with their food supply, return to feed on
warfarin treated baits again and again. Thus the problem of bait shyness is largely
overcome. At the same time, hazards to other animals from single accidental feedings
is greatly reduced. Since repeated feedings are required, permanent covered bait
stations provide an excellent technique for exposure; relatively large supplies of bait
obviate the necessity for daily care. Warfarin possesses the added advantage of being
effective against all species of rats and mice.

Much of the research in rodenticides today is directed along the lines of the
anti-coagulants. Used dry, in a cereal mixture such as cornmeal, or with a little
oil added to prevent dusting, insects and mold may attack the finished product. Most
insecticides and mold inhibitors leave objectionable tastes that cause marked reduction
in acceptance, so investigations are being made of candidate materials to overcome
this problem. Although warfarin is exposed in such dilute mixtures that primary
poisoning by accident would require the ingestion of a huge quantity of bait, that
occasionally has happened. Also, a few cases of secondary poisoning have been
reported, due to pets feeding daily on dead or dying rats or mice poisoned with
warfarin. Efforts should be made, then, to recover rodent carcasses whenever
possible. As with other poisons, the majority of complaints of warfarin failure can
be ascribed to faulty technique in exposure or failure to maintain a fresh, acceptable
bait supply until the entire rat colony has been eliminated. Since some rats may not
start feeding on the bait until it has been exposed for some time, or feeding may be
intermittant, two or three weeks may be necessary to produce results; a mouse colony
may require as long as thirty days to complete their removal.

No mention has been made of desirable bait materials, since local availability
and cost are determining factors. Then too, acceptance is so widely varied, even on
adjacent premises, that selection must be left to the judgment of the operator. Often
only trial and error will provide the correct answer, pre-baiting being the most useful
technique. Here, again, knowledge of the characteristics of the various poisons is
important, as many of the bait formulations are based on the specific chemical that is
used. Weather conditions should be considered before exposure. Above all, hazards
to other animals must receive top attention; using materials and employing techniques
best calculated to destroy rodents without attracting or being easily available to others.

The destruction of rats and mice is one of the important steps in attaining
permanent rodent control. Poisons represent the most efficient and useful tools in
accomplishing this end. Full advantage should be taken of the particular characteristics
of each of the rodenticides, selecting those most likely to produce the desired results
under the specific conditions where they are being used.

ware wee COUT wact? -™ fra) OS