A 2.0% zinc phosphide pellet and a 0.001% brodifacoum bait gave the lowest percentage post-treatment activity in a field test in which broadcast applications were followed shortly by rain. There was not a clear difference in performance between the single-feeding toxicants and the multiple-feeding anticoagulants in this experiment. A 0.075% cholecalciferol bait gave control comparable to some registered materials and shows promise for future development. A bait containing 0.0216% diphacinone gave significantly better control than one containing 0.005% diphacinone

Byers, R. E.

Merson, M. H.

English

DigitalCommons@University of Nebraska

University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln Eastern Pine and Meadow Vole Symposia Wildlife Damage Management, Internet Center for March 1983 RESULTS OF 1982 RODENTICIDE FIELD TESTS M. H. Merson Virginia Polytechnic Institute and State University R. E. Byers Virginia Polytechnic Institute and State University Follow this and additional works at: https://digitalcommons.unl.edu/voles  Part of the Environmental Health and Protection Commons Merson, M. H. and Byers, R. E., "RESULTS OF 1982 RODENTICIDE FIELD TESTS" (1983). Eastern Pine and Meadow Vole Symposia. 170. https://digitalcommons.unl.edu/voles/170 This Article is brought to you for free and open access by the Wildlife Damage Management, Internet Center for at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Eastern Pine and Meadow Vole Symposia by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. 13RESULTS OF 1982 RODENTICIDE FIELD TESTSM. H. Merson and R. E. ByersWinchester Fruit Research LaboratoryVirginia Polytechnic Institute and State UniversityWinchester, VA 22601Abstract: A 2.0% zinc phosphide pellet and a 0.001% brodifacoum baitgave the lowest percentage post-treatment activity in a field test inwhich broadcast applications were followed shortly by rain. There wasnot a clear difference in performance between the single-feeding toxi-cants and the multiple-feeding anticoagulants in this experiment. A0.075% cholecalciferol bait gave control comparable to some registeredmaterials and shows promise for future development. A bait containing0.0216% diphacinone gave significantly better control than one contain-ing 0.005% diphacinone.IntroductionIn the fall of 1982 eight rodenticide compounds were tested forefficacy in orchards against pine voles (Microtus pinetorum) and meadowvoles (~. pennsylvanicus). Three of the compounds (diphacinone,chlorophacinone, and zinc phosphide) are currently registered for useagainst field rodents. Pival, brodifacoum, and bromadiolone are cur-rently registered only for use against commensal rodents. In addition,two relatively new materials for rodent control in the U.S., reserpineand cholecalciferol, were tested.Two tests were performed. The first was designed to examine theeffect of precipitation immediately after bait application on theefficacy of mechanically broadcast bait treatments. Included in thisexperiment were handplaced treatments of reserpine and cholecalciferol.The second experiment compared the relative effectiveness of diphacinonebaits of two different concentrations applied at two different rates.MethodsField tests were conducted using a randomized complete block design.Each treatment (material and rate combination) was replicated three timesin randomly selected plots within blocks. Plots were blocked accordingto high, medium, and low activity from data collected in the firstactivity reading.Bait efficacy was determined on the basis of pre- and post-treatmentapple index activity readings and a final post-treatment trap-out of allplots. A more detailed description of the methods u~ed has been publishedpreviously (Byers, 1981).In the first test, broadcast applications of a 0.005% pival bait(Contrax-P), a 0.005% diphacinone bait (Ramik brown), a 0.005%bromadiolone bait (MAKI), a 0.005% chlorophacinone bait (Rozol), a 0.001%brodifacoum bait (VOLID), and two 2.0% zinc phosphide baits (ZP RodentBait AG and ZP Rodent Bait-Special) were made using a tractor-mountedmechanical spreader on 12 November 1982. Precipitation was expected that14evening. Hand placements of 0.01% reserpine and 0.075% cholecalciferolbaits were made under roofing shingle covers on 16 November 1982.In the second test, diphacinone baits (Ramik brown) containing 0.005%and 0.0216% active ingredient were mechanically broadcast at two differentrates. Included in the test for comparative purposes was another anti-coagulant bait containing 0.005% chlorophacinone (Rozol).Results and DiscussionIn the first test, 7.62 mm (0.30 in) precipitation fell in the 48hours beginning at 1830 hours on 12 November 1982. All the materialsbroadcast significantly reduced post-treatment activity levels belowthose in untreated control plots (Table 1). The greatest differencesbetween materials occurred in the percentage of sites active post-treatment. The trends in voles trapped per plot post-treatment and volesper site tended to follow the trends seen in percent active sites, butthere were few significant differences between materials for thesevariables.ZP Rodent Bait AG and brodifacoum bait (VOLID) plots averagedsignificantly (P < .10) fewer percent active sites than all other ma-terials tested. The original hypothesis was that the single-feedingmaterials (zinc phosphide, brodifacoum, bromadialone) would outperformthe multiple-feeding baits (chlorophacinone, diphacinone, pival) insituations where precipitation might make the baits unavailable or un-acceptable soon after treatment. In such cases, ample time would not beavailable for the voles to feed sufficiently on the multiple-feedingbaits to obtain a lethal dose.The results obtained with VOLID and ZP Rodent Bait AG are consistentwith this hypothesis, but , exceptions occurred in the case of Rozol, whichperformed as well as ZP Rodent Bait-Special, and MAKI which left thehighest post-treatment activity of any material. This inconsistencycannot be explained on the basis of the ability of the pellets to with-stand weather and consequent availability. Pellets of all materialscould be found 5 days post-treatment. Rozol appeared to be most ad-versely affected by the rain, but performed about average in the test.In contrast, MAKI pellets were affected very little by the rain andcould be found readily in the treated plots, but MAKI gave relativelypoor reductions in activity. This suggests that factors other thanweatherability such as bait acceptability were also operative.The handplaced treatment of cholecalciferol gave control comparableto that of some of the registered rodenticides (Table 1). Modificationsin the formulation could possibly improve the performance of cholecalci-ferol to the point where it would be commercially competitive. Reserpinegave relatively poor control. This could be due to the vole speciescomposition found in the test orchard which was almost exclusively pinevoles. Poorer results have been obtained in laboratory tests withreserpine against pine voles than against meadow voles (Merson and Byers,unpublished).15In the second field test, there was a marked difference in perfor-mance between the 0.005% and 0.0216% diphacinone baits (Table 2). The0.005% diphacinone bait left significantly (P < .10) more activity post-treatment than the 0.0216% diphacinone or the 0.005% chlorophacinonebaits. The improved performance of diphacinone relative to chlorophacinone,which was achieved by increasing the concentration of diphacinone 4-fold,is consistent with what is known about the toxicity of these materialsand illustrates the need to match bait concentrations with the toxicity tothe target organisms. The observation that essentially the same level ofcontrol was obtained with the 13.1 kg/ha rate of application of the 0.0216%diphacinone bait as with the 23.1 kg/ha rate could indicate that some down-ward adjustment in the 23.1 kg/ha rate could be made without compromisingefficacy.Literature CitedByers, R. E. 1978. Performance of rodenticides for the control of pinevoles in orchards. J. Amer. Soc. Hort. Sci. 103(1):65-69.Byers, R. E. 1982. Field method for evaluation of rodenticides forcontrol of Microtus pinetorum in apple orchards. Pages 77-85 inE. W. Schafer, Jr. and C. R. Walker, eds. Vertebrate Pest Controland Management Materials, Third Conf. ASTM STP 752. AmericanSociety for Testing Materials.Table 1. Results of a field test of rodenticide baits broadcast or handplaced to control meadow andpine voles in a Virginia orchard. November 1982.Highl~ activeActive sitesw(%)Vole~ per Vole~ per%Rate No. sites (%) plot siteMaterial (kg/ha) plots 3 Nov 30 Nov 3 Nov 30 Nov 2-7 Dec 2-7 Dec ControlBroadcastYControl 3 81 aV 73 a 91 a 94 a 35.0 a 1.17 a 0Pival 0.005% 21.6 3 80 a 11 bc 90 a 33 bc 5.3 bc 0.18 bc 85(Contrax-P)Bromadiolone 0.005% 12.7 3 76 a 26 b 86 a 48 b 10.0 bc 0.33 bc 71(Maki)Diphacinone 0.005% 24.2 3 78 a 23 b 93 a 39 bc 13.3 b 0.45 b 62(Ramik brown).....Chlorophacinone 0\0.005% (Rozol) 19.6 3 78 a 7 c 92 a 26 cd 4.7 c 0.16 bc 86Brodifacoum 0.001% 14.1 3 73 a 2 c 89 a 16 de 3.3 c 0.11 c 91(Volid)Zinc phosphide 2.0% 11.3 3 69 a 3 c 89 a 27 cd 6.0 bc 0.20 bc 82(ZP Rodent Bait-Special)Zinc phosphide 2.0% 10.4 3 71a 3 c 87 a 9 e 2.7 c 0.09 c 92(7P Rodent Bait AG)Table 1. Results of a field test of rodenticide baits broadcast or handp1aced to control meadow andpine voles in a Virginia orchard, November 1982, continuedHigh1~ activeActive sitesw(%)Vo1el per Vo1el per%Rate No. sites (%) plot siteMaterial (kgjha) plots 3 Nov 30 Nov 3 Nov 30 Nov 2-7 Dec 2-7 Dec ControlHandp1acedzControl 3 81 a 73 a 91 a 94 a 35.0 a 1.17 a 0Cholecalciferol0.075% 11.2 3 73 a 22 bc 94 a 34 bc 8.7 b 0.31 b 75Reserpine 0.01% 11.2 3 83 a 31 b 92 a 52 b 17.7 ab 0.61 ab 50Zinc phosphide 2.0% 2.2-3.4 3 80 a 7 c 88 a 10 c 3.3 b 0.11 b 91(ZP Rodent Bait AG)......w Values transformed to arcsine ,,..------v for analysisx Values transformed to V X+O.5 for analysis.y Treatment on 12 November 1982, 7.62 mm precipitation in the 48 hours after treatment.z Handp1acement on 16 November 1982.v Mean separation by Duncan's multiple range test, 10% level.Table 2. Results of a field test of diphacinone (DPN) and chlorophacinone (CPN) baits broadcast for thecontrol of meadow and pine voles in a Virginia orchard 6 Dec 1982.Highl~ activeActive sitesx (%)Voles perRate No. sites (%) plotYMaterial (kg/ha) plots 30 Nov 23 Dec 30 Nov 23 Dec 27-31 DecControl 3 83 az 80 a 100 a 92 a 39.3 aDPN 0.005%v 11.4 3 84 a 37 b 99 a 50 b 13.0 beDPN 0.005%v 19.3 3 85 a 46 b 100 a 69 b 20.0 abDPN 0.02l6%v 13.1 3 81 a 9 c 99 a 19 c 5.3 cdDPN 0.02l6%v 23.1 3 84 a 5 c 100 a 18 c 4.0 cdCPN 0.005%w 24.6 3 86 a 5 c 100 a 9 c 1.7dvole~ persite27-31 Dec1.31 a0.43 be0.65 b0.18 c0.13 c0.06 c%Con.!:.rol067498790~ex>96x Values transformed to arcsine v--x--- for analysis.Y Values transformed to~ for analysis.z Mean separation by Duncan's multiple range test, 10% level.v Ramik brown formulation.w Rozol pellet.

RESULTS OF 1982 RODENTICIDE FIELD TESTS

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University of Nebraska - Lincoln 
DigitalCommons@University of Nebraska - Lincoln 
Eastern Pine and Meadow Vole Symposia Wildlife Damage Management, Internet Center for 
March 1983 
RESULTS OF 1982 RODENTICIDE FIELD TESTS 
M. H. Merson 
Virginia Polytechnic Institute and State University 
R. E. Byers 
Virginia Polytechnic Institute and State University 
Follow this and additional works at: https://digitalcommons.unl.edu/voles 
 Part of the Environmental Health and Protection Commons 
Merson, M. H. and Byers, R. E., "RESULTS OF 1982 RODENTICIDE FIELD TESTS" (1983). Eastern Pine and 
Meadow Vole Symposia. 170. 
https://digitalcommons.unl.edu/voles/170 
This Article is brought to you for free and open access by the Wildlife Damage Management, Internet Center for at 
DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Eastern Pine and Meadow 
Vole Symposia by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. 
13
RESULTS OF 1982 RODENTICIDE FIELD TESTS
M. H. Merson and R. E. Byers
Winchester Fruit Research Laboratory
Virginia Polytechnic Institute and State University
Winchester, VA 22601
Abstract: A 2.0% zinc phosphide pellet and a 0.001% brodifacoum bait
gave the lowest percentage post-treatment activity in a field test in
which broadcast applications were followed shortly by rain. There was
not a clear difference in performance between the single-feeding toxi-
cants and the multiple-feeding anticoagulants in this experiment. A
0.075% cholecalciferol bait gave control comparable to some registered
materials and shows promise for future development. A bait containing
0.0216% diphacinone gave significantly better control than one contain-
ing 0.005% diphacinone.
Introduction
In the fall of 1982 eight rodenticide compounds were tested for
efficacy in orchards against pine voles (Microtus pinetorum) and meadow
voles (~. pennsylvanicus). Three of the compounds (diphacinone,
chlorophacinone, and zinc phosphide) are currently registered for use
against field rodents. Pival, brodifacoum, and bromadiolone are cur-
rently registered only for use against commensal rodents. In addition,
two relatively new materials for rodent control in the U.S., reserpine
and cholecalciferol, were tested.
Two tests were performed. The first was designed to examine the
effect of precipitation immediately after bait application on the
efficacy of mechanically broadcast bait treatments. Included in this
experiment were handplaced treatments of reserpine and cholecalciferol.
The second experiment compared the relative effectiveness of diphacinone
baits of two different concentrations applied at two different rates.
Methods
Field tests were conducted using a randomized complete block design.
Each treatment (material and rate combination) was replicated three times
in randomly selected plots within blocks. Plots were blocked according
to high, medium, and low activity from data collected in the first
activity reading.
Bait efficacy was determined on the basis of pre- and post-treatment
apple index activity readings and a final post-treatment trap-out of all
plots. A more detailed description of the methods u~ed has been published
previously (Byers, 1981).
In the first test, broadcast applications of a 0.005% pival bait
(Contrax-P), a 0.005% diphacinone bait (Ramik brown), a 0.005%
bromadiolone bait (MAKI), a 0.005% chlorophacinone bait (Rozol), a 0.001%
brodifacoum bait (VOLID), and two 2.0% zinc phosphide baits (ZP Rodent
Bait AG and ZP Rodent Bait-Special) were made using a tractor-mounted
mechanical spreader on 12 November 1982. Precipitation was expected that
14
evening. Hand placements of 0.01% reserpine and 0.075% cholecalciferol
baits were made under roofing shingle covers on 16 November 1982.
In the second test, diphacinone baits (Ramik brown) containing 0.005%
and 0.0216% active ingredient were mechanically broadcast at two different
rates. Included in the test for comparative purposes was another anti-
coagulant bait containing 0.005% chlorophacinone (Rozol).
Results and Discussion
In the first test, 7.62 mm (0.30 in) precipitation fell in the 48
hours beginning at 1830 hours on 12 November 1982. All the materials
broadcast significantly reduced post-treatment activity levels below
those in untreated control plots (Table 1). The greatest differences
between materials occurred in the percentage of sites active post-
treatment. The trends in voles trapped per plot post-treatment and voles
per site tended to follow the trends seen in percent active sites, but
there were few significant differences between materials for these
variables.
ZP Rodent Bait AG and brodifacoum bait (VOLID) plots averaged
significantly (P < .10) fewer percent active sites than all other ma-
terials tested. The original hypothesis was that the single-feeding
materials (zinc phosphide, brodifacoum, bromadialone) would outperform
the multiple-feeding baits (chlorophacinone, diphacinone, pival) in
situations where precipitation might make the baits unavailable or un-
acceptable soon after treatment. In such cases, ample time would not be
available for the voles to feed sufficiently on the multiple-feeding
baits to obtain a lethal dose.
The results obtained with VOLID and ZP Rodent Bait AG are consistent
with this hypothesis, but , exceptions occurred in the case of Rozol, which
performed as well as ZP Rodent Bait-Special, and MAKI which left the
highest post-treatment activity of any material. This inconsistency
cannot be explained on the basis of the ability of the pellets to with-
stand weather and consequent availability. Pellets of all materials
could be found 5 days post-treatment. Rozol appeared to be most ad-
versely affected by the rain, but performed about average in the test.
In contrast, MAKI pellets were affected very little by the rain and
could be found readily in the treated plots, but MAKI gave relatively
poor reductions in activity. This suggests that factors other than
weatherability such as bait acceptability were also operative.
The handplaced treatment of cholecalciferol gave control comparable
to that of some of the registered rodenticides (Table 1). Modifications
in the formulation could possibly improve the performance of cholecalci-
ferol to the point where it would be commercially competitive. Reserpine
gave relatively poor control. This could be due to the vole species
composition found in the test orchard which was almost exclusively pine
voles. Poorer results have been obtained in laboratory tests with
reserpine against pine voles than against meadow voles (Merson and Byers,
unpublished).
15
In the second field test, there was a marked difference in perfor-
mance between the 0.005% and 0.0216% diphacinone baits (Table 2). The
0.005% diphacinone bait left significantly (P < .10) more activity post-
treatment than the 0.0216% diphacinone or the 0.005% chlorophacinone
baits. The improved performance of diphacinone relative to chlorophacinone,
which was achieved by increasing the concentration of diphacinone 4-fold,
is consistent with what is known about the toxicity of these materials
and illustrates the need to match bait concentrations with the toxicity to
the target organisms. The observation that essentially the same level of
control was obtained with the 13.1 kg/ha rate of application of the 0.0216%
diphacinone bait as with the 23.1 kg/ha rate could indicate that some down-
ward adjustment in the 23.1 kg/ha rate could be made without compromising
efficacy.
Literature Cited
Byers, R. E. 1978. Performance of rodenticides for the control of pine
voles in orchards. J. Amer. Soc. Hort. Sci. 103(1):65-69.
Byers, R. E. 1982. Field method for evaluation of rodenticides for
control of Microtus pinetorum in apple orchards. Pages 77-85 in
E. W. Schafer, Jr. and C. R. Walker, eds. Vertebrate Pest Control
and Management Materials, Third Conf. ASTM STP 752. American
Society for Testing Materials.
Table 1. Results of a field test of rodenticide baits broadcast or handplaced to control meadow and
pine voles in a Virginia orchard. November 1982.
Highl~ active
Active sitesw(%)
Vole~ per Vole~ per
%Rate No. sites (%) plot site
Material (kg/ha) plots 3 Nov 30 Nov 3 Nov 30 Nov 2-7 Dec 2-7 Dec Control
BroadcastY
Control 3 81 aV 73 a 91 a 94 a 35.0 a 1.17 a 0
Pival 0.005% 21.6 3 80 a 11 bc 90 a 33 bc 5.3 bc 0.18 bc 85
(Contrax-P)
Bromadiolone 0.005% 12.7 3 76 a 26 b 86 a 48 b 10.0 bc 0.33 bc 71
(Maki)
Diphacinone 0.005% 24.2 3 78 a 23 b 93 a 39 bc 13.3 b 0.45 b 62
(Ramik brown)
.....
Chlorophacinone 0\
0.005% (Rozol) 19.6 3 78 a 7 c 92 a 26 cd 4.7 c 0.16 bc 86
Brodifacoum 0.001% 14.1 3 73 a 2 c 89 a 16 de 3.3 c 0.11 c 91
(Volid)
Zinc phosphide 2.0% 11.3 3 69 a 3 c 89 a 27 cd 6.0 bc 0.20 bc 82
(ZP Rodent Bait-
Special)
Zinc phosphide 2.0% 10.4 3 71a 3 c 87 a 9 e 2.7 c 0.09 c 92
(7P Rodent Bait AG)
Table 1. Results of a field test of rodenticide baits broadcast or handp1aced to control meadow and
pine voles in a Virginia orchard, November 1982, continued
High1~ active
Active sitesw(%)
Vo1el per Vo1el per
%Rate No. sites (%) plot site
Material (kgjha) plots 3 Nov 30 Nov 3 Nov 30 Nov 2-7 Dec 2-7 Dec Control
Handp1acedz
Control 3 81 a 73 a 91 a 94 a 35.0 a 1.17 a 0
Cholecalciferol
0.075% 11.2 3 73 a 22 bc 94 a 34 bc 8.7 b 0.31 b 75
Reserpine 0.01% 11.2 3 83 a 31 b 92 a 52 b 17.7 ab 0.61 ab 50
Zinc phosphide 2.0% 2.2-3.4 3 80 a 7 c 88 a 10 c 3.3 b 0.11 b 91
(ZP Rodent Bait AG)
......
w Values transformed to arcsine ,,..------v for analysis
x Values transformed to V X+O.5 for analysis.
y Treatment on 12 November 1982, 7.62 mm precipitation in the 48 hours after treatment.
z Handp1acement on 16 November 1982.
v Mean separation by Duncan's multiple range test, 10% level.
Table 2. Results of a field test of diphacinone (DPN) and chlorophacinone (CPN) baits broadcast for the
control of meadow and pine voles in a Virginia orchard 6 Dec 1982.
Highl~ active
Active sitesx (%)
Voles per
Rate No. sites (%) plotY
Material (kg/ha) plots 30 Nov 23 Dec 30 Nov 23 Dec 27-31 Dec
Control 3 83 az 80 a 100 a 92 a 39.3 a
DPN 0.005%v 11.4 3 84 a 37 b 99 a 50 b 13.0 be
DPN 0.005%v 19.3 3 85 a 46 b 100 a 69 b 20.0 ab
DPN 0.02l6%v 13.1 3 81 a 9 c 99 a 19 c 5.3 cd
DPN 0.02l6%v 23.1 3 84 a 5 c 100 a 18 c 4.0 cd
CPN 0.005%w 24.6 3 86 a 5 c 100 a 9 c 1.7d
vole~ per
site
27-31 Dec
1.31 a
0.43 be
0.65 b
0.18 c
0.13 c
0.06 c
%
Con.!:.rol
0
67
49
87
90
~
ex>
96
x Values transformed to arcsine v--x--- for analysis.
Y Values transformed to~ for analysis.
z Mean separation by Duncan's multiple range test, 10% level.
v Ramik brown formulation.
w Rozol pellet.


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RESULTS OF 1982 RODENTICIDE FIELD TESTS

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