HORN FLY, HAEMATOM IRRITANS (L.), RESISTANCE IN ONTARIO TO PYRETHROID AND ORGANOPHOSPHOROUS INSECTICIDES IMPREGNATED IN CA= EAR TAGS A Thesis Presented to The Facuity of Graduate Studies of The University of Guelph by SARAH M. BUTLER In partial fulfilment of requirements for the degree of Master of Science August, 1999 @ Sarah M. Butler, 1999
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HORN FLY, HAEMATOM IRRITANS (L.), RESISTANCE IN ONTARIO TO
PYRETHROID AND ORGANOPHOSPHOROUS INSECTICIDES IMPREGNATED
IN CA= EAR TAGS
A Thesis
Presented to
The Facuity of Graduate Studies
of
The University of Guelph
by
SARAH M. BUTLER
In partial fulfilment of requirements
for the degree of
Master of Science
August, 1999
@ Sarah M. Butler, 1999
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HORN FLY, HAEMATOBLQ IRRlTANS (L.), RESISTANCE IN ONTARIO TO
PYRJZHROID AND ORGANOPHOSPHOROUS INSECTICIDES IMPREGNATED
IN CA= EAR TAGS
Sarah M. Butler University of Guelph, 1999
Horn fly, Huemcltobiu im5mrs
organophosphorous insecticides impregnatec
a-) 9
d in cati
Advisor: Dr, G-A- Surgeoner
raistance to pyrethroid and
Ne ear tags was monitored by tag
efficacy evaluation in Perth, and by gIass tube bioassay in Perth and Glencœ, Oatario.
Location, ear tag treatrnent, and description of cattle and pasture shade conditions of f m used in 1997 and 1998, Perth, Ontario. Farm
........ numbers wf~:espond to numbered locations in Figure 1. -18
LC, LG, and resistance ratios ofpyrethroid and organophosphorous- resistant hom fies fiom Perth and Glencoe, ûntario, and susceptible flies from Rockwood, Ontario, detefmined &er 3 hours exposure to federate, 1998,. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . - 42
LC, LC9, and resistance ratios of pyrethroid and organophospborous- resistant hom fies fiom Perth and Glencoe, Ontario, and suscepti'ble flies fiom Rockwood, Ontario, determineci &er 24 hours exposure to diazinon, 1998 ........................................ . .47
iii
LTsr OF FIGURES
Figure 1 Location of fauns at Perth, Ontario for the 1997 and 1998 ear tag .................................. efficacy study. -19
Figure 2 Mean number (+ SE) of hom fies (Huemafo~iu i r r i ~ ) per side ofcattIe (n=lO) at Perth, Ontario, that were non-treated (location 3) or were treated with two Protecto? (2Q96 diazhon wlw) ear tags @cation 2). Significant diffierences (PsO.05) between ~rotectop and the non-treated animais are
................................. indicated by an asterisk (*). 3 1
Figure 3 Mean nimber (+ SE) of hom flies (Haem~lrobia imm) per side ofcattle (n=lO) at Perth, Ontaxio. that were noa-treated (Iocation 3) or were tnated with two ~ c t o g u a r d ~ (LW tetrachlorvinphos wlw) ear tags (location 6). Significant Merences Qa0.05) between Ectoguardo and the non-treated anirnals are indicated by an asterisk (*). ......................... 32
Figure 4 Mean number (+ SE) of horn fiies (Haemutobia imfm) per side ofcattle (n=10) at Perth, Ontario, that were non-treated (iocation 3) or were treated with two Stocka@' (8% cypermethrin w/w) eu tags (location 5). Signincant ciifFerences Ps0.05) between Stockaido and the non-treated animais are indicated by an asterisk (*). ........................ 33
Figure 5 Mean number (+ SE) of horn nies (Huematobia Mtcms) per side of cattle (n=10) at Perth, Ontario, that were non-treated (location 3) or were treated with two ~lirninator~ (1 1% diazinon, 6% cypermethrin wlw) ear tags (iocation 4). Significant merences (Ps0.05) between ~liminat0P and the
............... non-treated animals are indicated by an asterisk (*). -34
Figure 6 Mean number of hom fies (Haemutobia imiftms) per side of cattle (n = 10) at Perth, Ontario, that are non-treated or are tteated with two ~rotector~ (20 % diazinon wfw), two &toguardœ (10 % tewchlo~nphos wfw), two stockaïde (8 % cypermethrin w/w), or two E l i m i n a d (11 % diazinon and 6 % cypemethrin wlw) ear tags, 1997. .......... -35
Figure 7 Mean number (+ SE) of hom flies (Haemattobia i r r i ~ ) per side of cade (n=10) at Perth, Ontario, that were non-treated (location 3) or were treated with two ~rotector* (20% diazhon w/w) ear tags (location 1). Significant diierences (Pr0.05) between Protectorœ and the non-treateà animals are indicated by an astensk (*). ................................. -36
Figure 8 Mean number (+ SE) ofhorn Ses (Haematoobia intant) per side o f d e (n=10) at Perth, Ontarh, that are non-treated (location 3) or are treated with two Ectogud (1% tetrachlominphos w/w) ear tags (iocation 6). Si@cant daféruices (Ps0.05) between -oguardo and the non-treated
........................ anirnals are indicated by an astaisk (*). -37
Figure 9 Mean numba (+ SE) of hom fies (Haematobiu irritclns) per side of cattle @=IO) at Perth, Ontario, that are non-treated (location 3) or are treated with two Bovaidœ (8% fenvafemte w/w) ear tags (iocation 5). Sipinuint ditferences (Ps0.05) between Bovaidœ and the non-treated animals are indicated by an asterisk (*). ................................. - 3 8
Figure 10 Mean nuniber (+ SE) ofhom fies (tiixmaiobiu imrons) per side o f d e @=IO) at Ped~ , -*O, that are non-treated (location 3) or are treated with two Elirninato~ (1 1% diazinon and 6% cypermethiin wlw) ear tags (location 4). SisnifiCant differences @sO.OS) between ~fiminator@' and the non-treated animals are indicated by an asterisk (*). .............. .39
Figure 1 1 Mean number of hom nies (Haentcltobiu ikriiarrs) per side of cattie (n= 10) at Perth, Ontario, that are non-treateû or are treated with two Protectorœ (2û% diazinon wlw), two Ectoguardœ (100h tetrachiorvinphos wlw), two Bovaid. (8% fenvalerate w/w), or two Eliminator@ (1 1% d i d o n and 6% cypermetbrin wfw) ear tags, 1998. ............... -40
Figure 12 Mortality dose-response with 95 % confidence limits for pyrethroid and organophosphorous-cesistant hom flies (Haematobia iet411s)
LC, =O.Os8 fkom Perth, Ontario, and susceptible flies LC,=O. 15xlû3 fiom RockWood, Ontario, exposed to fenvalerate for 3 hours, July
Figure 13 Mortality dose-response with 95 1 confidence limits for pyrethroid and organophosphorous-resistant hom flies (Hmmatobia imtMI) ~ ~ ~ = 0 . 4 l x l û ~ fkom Penh, Ontario, and susceptible flies ~C,=0.45~10~ fkom Rockwood, Ontario, exposed to fenderate for 3 hours, August 20121, 1998. ........................... -44
Figure 14 Mortality dose-response with 95 %-confidence limits for pyrethroid ancl organophosphorous-resistant hom flies ( H m ~ o b i a imlmrr) LC,=O. 12 fiom Glencoe, Ontario, and suscepti.%le flies ~C,=0.45~10~ from Rockwood, Ontario, exposed to fenvaierate for 3 hom, August 20/21, 1998 ..................................... . . . . . 45
Figure 15 Mortaiity dose-response with 95% confidence limits for pyrethroid and organophosphorous-resistant horn flies (Hmmatobia im't~~t~) KM = 1-29 from Perth, Ontario, and susceptible flies LC,=0.59 from Rockwood,
... Ontario. exposed to diazinon for 24 hours, August 20/21, 1998. 48
Figure 16 Mortdity doee-response with 95% confidence limits for pyrethroid and organophosphorous-raistant horn flies (Haem4tobt'a irn'tm) LCC = 1.94 fcom Glencae, Ontario, and susceptiile flies LC, = O . S fiom Rockwood, Ontario, expoJed to diazinon for 24 hours, August 20/21, 1998 .......................................... 49
Figure 17 Mortality dose-responre with 95% confidence limits for pyrethroid and organophosphorous-resistant horn flies (Hcumatobia imtmrr) LCm =O.Ol3 nom Perth, Ontario, e x p d to chlorfenapyr for 24 hours, September 4, 1998. Morialiîy of susceptible flies from RockWood, Ontario. was 1 0 % at d l concentrations presented. ........... -51
Figure 18 Mortality dose-response with 95 % confidence limits for pyrethroid and organophosphorous-tesistant horn flies (Hocmatobia irriians) LC,=0.012 fkom Glencoe, Ontario, exposecl to chlodenapyr for 24 hours, September 5, 1998. Mortality of susceptible nies fkom
. . . . Rockwood, Ontario, was 100% at al1 concentrations presented 52
Figure 19 Percent of inhibited acetylcholinesterase activity in pyrethroid and organophoaphorous-resistant horn fly (Haemutobia irn?izns) heads fiom Perth and Glencoe, Ontario, and susceptible horn fiies nom Rockwood, Ontario exposed to wncentratiom of diazinon for 24 hours, August 20
Acetylchoünesterase is an enzyme located in the post-synaptic membrane and
fiuctions to hydrolyse the esta bond ofthe neurotransmitter acetylcbobe- Inhibition of tbis
enzyme by the irreversiôle binding of ocgaaophosphorous compouads resuits in the
accumulation ofacetylchohe Pt the synapse.
Inhibition of acetylchoiinesterase can be quantified through the detemination of
acetylcholinesterase activity (Eliman a al. 1961) when standardid to protein concentration
(Bradford 1976). The colorimetric assays, wbich have been adopted to a microplate r d e r
(Galgani and Boquene 199 1). provide an indication of acetyIcholinesterase activity @ h a n
et al. 1961).
3.5.1 Determ0n&n of Acetylckou'nalape Acft0vily
Acetylcholinesterase levels in adult hom fiies were measured using the methd of
Ehan et al. (1 961). in which the hydrolysis ofthe substrate analogue acetylthiocholw iodide
(ATChI) is measured colorirnetridy by the absorbance of2-nitro-S-tbi0berizoate at 405 nxn,
after the r d o n of S,S'-dithiobis-2-nitrobenu,ic acid @TNB) with the i i i thiocholine.
Kinetic reactions were monitored using a microplate reader that determines wan
acetylcholinesterase adivities by linear regrasions of absorbante-thne data @bores a ai.
1988)-
Hom flies were coiiected fiom Perth, Glenca, and Rodouood, aspiratad into the
glass bioassay tubes, and provided with a citrated bovine blood meai as dcscribcd above (p.
22). Pyrethroid and organophosphorou&nsistant Penh and Glencoe, and ~~1scepti'ble
Rockwood hom fies were exposed for 24 hours to concentrations of d i d o n mghg fiom
0.13 &cm2 to 5.0 &cm2. Approximately 20 hom fiies nom each location wae kcpt in non-
treated glas tubes (1 ml acetone only) as wntrols. After 24 hours ~ t p o s w , flics were
wllected and fiozen at -80°C (Xu Md B d 1994). Smples wac Lcpt at -80°C and were
analysed 4 7 and 9 weeks ifta coliection. Ffy hads, which contain 72.9% of totd body
acetylcholinesterase (Xu and Bull 1994). w a e rernoved and hornogenates of 5 hcads were
made in 8 ml of phosphate buff i (pH 7.2). Sampkr were caitrifirged for 20 minutes at
10,000 x g. Thme 30 pl aiiquots of eich sample wae placed in a % wdl niaoplate. DTM)
(30 J )(Sigma D-8130) and 100 3 phosphate buffer @H 7.9) were added to each sample
well and inaibatad for 10 minutes. After incubation 30 pl of ATCM (Sigma A-5751) was
added to each sample weU. Activity was measured using a Bio-Rad (mode1 3550-UV)
microplate reader at 405 rn for 10 minutes. Absohance readings were made at 1 minute
intervais, Sumng each microplate M o r e each reading. Protein concentrations ofthe samplcs
were detennined fiom a standard avve developcd with bovine m m aibumin (Pierce 23209)
as desaibed by Bradford (1 976). Acetylcholinata~se activity was calcufated using the
formula (EUman et al. 1% 1):
Activity= * absmefFx light path x ample volume
AA change in absorbana (OD) &S. weE 13.6 cm2 (absorbame d c i e n t ofthionitrobenzoic at 405 nm) Iight path 0.5547 cm for total volume of 190 pl
The standardized activity was CalcuIated ushg the fomuia @ d o r d 1976):
Standardîzed actîvity = Actikitv Protein concentration
4 RESULTS AND DISCUSSEON
4.1 Ear Tag Efïicacy 1997 and 1-
Weekly mean numbers of hom flies on cattie &Perth, Ontario treated with athatwo
~rotectoe (20% diazhon wlw). or two EctoguardO (lm tetrachlowinphos w/w), or two
Stockaid6 (8% cypemahrin w/w), or two EIuninetd (1 1% d*nnon, 6% cypennethrin
W/W) ear tags for the 1997 season are plotîed with the non-treated means in Figures 2 - 5.
Figure 6 summacÛes weekly mean n u m k n of horn fTies on cattle at Perth, Ontario for
al1 ueatments in 1997. Boch orgawphosphomus t p g ~ (Protector0and -do) provided
poor hom 8y wnuol in 1997. The Protecd (20% diazinon w/w) tags provided a
statistidy signincant reduction of honi flies as compared to the non-treated herd in the week
of June 27 and the week of September 5, 1997 Figure 2). The air temperature inaeased
nom daily highs of 20" C at the end of August to daiiy highs of 25 OC in the fint week of
September 1997, resulting in adult emefgence and thadore increased fSr numbers in
September. The ~rotecto? herd (location 2) may have experienced stati*sticaliy sigdcant
reductions of hom fies compamd to the non-treated herd (Iocation 3) in week 12 because
they had access to a 2 acre woodlot which provided shade and coola temperatures. Low
numbers of fies on control cattle throughout the season codd have r d t e d Born r@ar
manure removal ftom the feed bunk area located just outside the müking barn, thus reducing
the number of oviposition sites. As well, unseasonably dry conditions fbr the summer o f 1997
may have affected moisture content of manure, and thus reduced lame and pupae d v d .
The ~ctoguard' (10% tetrachlorvinphos wlw) tags provided statistically signifiant reduction
of fiies as wmpared to the non-treatcd herd for one week der tag application (F~igure 3).
27
The large increase in fly numbers on Ektogutud0 treated ca#k observed in the nnt week of
September 1997 may have resulted h m i n d addt emergeme because of warm
temperatures, and the low amount of s u e adable at this location (6) comparecl to o h
treatment locations. ûver the entire 1997 season, the ~otector' and Ectoguarde tags
provided no statistical season meui reduction in horn %es u cornpanxi to the non-treated
herd.
nie pyrethroid tag stockaid*@% cypennethrinw/w) provided statistidysigniûcaut
horn fly reduction as comparexi to the non-treated had in the weeks of Jdy 5, and August 24-
September 5,1997 (Figure 4). Cattie wae moved the wak ofhgust 16,1997 to a pasture
that had access to a wooded area ( i d o n 5). Stotisticaiiy signifiant reductions in homfly
numbers as compared to the non-treated herd for August 24 - Septanber 5, 1997 rnay have
been due to the increase in shade provided. Statisticaüy higher numbers of horn flies as
compared to the non-treated herd were o b d on cattle in the wadrs ofJuly 23 and August
8, 1997. Temperatures during the weeks fiom July 23 - Augua 8, 1997 ranged fkom daily
highs of 25-27°C. This increase in temperature may have contn'buted to increaseû
degradation of the pyrethroid on the animal, as well as increased metabolism in the bect.
Over the entire season, stockaidm provided a 23.8% reduction in horn fies as compared to
the non-treated herd.
The ~limu>ator' (1 1% diasinon, 6% cypermethrin wlw) wmb'mtion tag provïded
statisticaiiy signifiant reductions in horn fly numbers as compared to the non-treated &rd for
8 weeks after tag application Figure 5). ûva the enth seasm the ~liminator* tag reduccd
horn Ses by 71.7% as compareci to the non-treatd herd.
Weekly mean numbers of horn flics on cattie at Perth Ontano treated with either two
ProtectoP (20% diazinon w/w), or two Ectoguard0 (IW tetrachiorvinphos w/w), or two
~ o v a i d . (8% favalemte wlw), or two Eliminator@ (1 1% diainon, 6% cypametlnin wlw)
ear tags fot the 1998 sason are plotteci with the non-treated maris in Figures 7 - 10. Figure
11 sumrnarivs weekly mean number of hom flies on cattle at Perth, OMM0 for ali
treatments in 1998. The 1998 season was longer than the 1997 season- 16 weeks versus
12 weeb. respectively. Ullseasonably w a m temperatures in &y 1998 d t e d in ear1y
emergenœ of hom fly adults, -fore application of insecticide irnpregnatad ear tags was
earlier than in 1997.
nie protector (2% diazinon w/w) tags provided strtisticaiiy signiacant reductions
of hom fies as wmpared to the non-treated herd spofadically throughout the season (walr
of June 4,28, July 2.3 1, and August IO, 1998) (Figure 7). niaie statistical reductions may
the r d t of acass to more shade at the Protectop site (location 1). The Ectoguado (10./.
tetrachiorvinphos w/w) tags provided statistical hom fly reduction for 6 weeks post
application (Figure 8). Mer 6 weeks, horn fly numben increased on Ectoguard* ereated
animals to levels that were staîistidy signincantly higher than the non-treated animals. This
difference in fIy numbers may have beai because of mure management around the milking
barn at the wntrol hwd location (3), or besaust less shade was adable at the Ectoguard0
location (6). Over the entire 1998 season, both organophosphorous tags, Protectop a d
~ctoguardo, did not provide a statistically significant reduction in horn fly numkn as
compared to the non-ueated herd.
The pyrethroid tag Bovaidœ (8% fenvaierate w/w) provided statistcaily significant
horn fly reduction fiic 7 weeks post tag applÉltion (Figure 9). Afkr 7 mdo horn tly
numbers on Bovaida treated cattle were not statisticaily signifimtiy difkmt h m the
non-treated herd or were statistidy higher. Over the entire 1998 sauon, the ~ o v a i d ~ tag
did not provide a statistically significant reduction of horn aies as compareû to the non-
treated herd.
The Eliminatorm (1 1% diahon, 6% cypermethrin w/w) tag provided a statisticaily
significant reduction in horn flks fot the weeks of May 30 - August 10, with the exception
of the week of June 4 (Figure 10). Ova the 6 sason the ~liminatof' tag d u c c d fly
numbers by 60.1% as compared to the non-treated M.
Ali tags tested in the P d area in 1997 and 1998 were wasidaed Mures becwse
impregnated tags un d u c e horn fly numbas by to for the entire eason
(Ahrens and Cocke 1979; Miller et al. 1984; Byford a al. 1992; Surgeoncf et al. 1994),
indicating that resistance to both organophosphorous and pyrethroid mseaicides is ooamiag.
Sample Dates 1997
Figure 2 Mean number (+ SE) of horn fies (Haemotobia imi&am) per side of cattie @=IO) at Perth, Ontario, that were non-treated o d o n 3) or were treated with two Protectore (2W diazinon wlw) ea. tags (iocation 2). Signihmt differences (PzO.05) between Protecto? and the non-treaîed animais are indicaîed by an astensk (*).
Sample Oates 1997
Figure 3 Mean number (+ SE) of hom flies (Himaiobia hitans) per side of cattle @=IO) at Perth, Ontario, that were non-treated (iocation 3) or were treated with two Ectoguard0 (Io./. tetrachlorvinphos wh) ear t a p (location 6). Significant Mérrnces (Ps0.05) b e e n Ectoguardo and the non-treated animais an indideci by an asterisic (*).
Sample Dates 1997
Figure 4 Mean numba (+ SE) of hom fiies (Haemutobia irritaPts) per side o f d e @=IO) at Perth, Ontario, that were non-treated Gocation 3) or were treated with two Stockaido (8% cypermethrin wlw) ear tags (location 5). Signifiant dinerences (PrO.05) between Stockaida and the non-treated a n k d s are indicated by an asterisic (*).
Sample Dates 1997
Figure 5 Mean numba (+ SE) of hom fies (Nlematobia in+-) per side of cattle @=IO) at Perth, Ontario, that were non-treated flocation 3) or were treated with two Elimiaotor ( I l% diazinon, 6% cypermethrin wlw) ear tags (iocation 4). SipifIcant différences (Pr0.05) between ~liminnt~P and the non-treated animais are indicated by an asterisic (*).
(o~=u) ap!s rad sa!U uroy 40 raqurnu ueaw
é: 0 P Z ,
e Sample Dates 1998
Figure 7 Mean number (+ SE) of hom fües (Haematobiu Mians) per side of c d e (n=lO) at Perth, Ontario, that were non-treated (location 3) or were treated with two Protaop (2% diainon w/w) ear tags gocation 1). Signincant differences (Ps 0.05) betweai protector@ and the non-treated anirnals are indicated by an asterisk (*).
QI' Sample Dates 1998
Figure 8 Mean number (+ SE) of hom fies (Hmm4fobia imtons) per side of d e (n=lO) at Perth, Ontario, that are non-treated (location 3) or are treated with two Ectoguardm (1W tetrachlocvinphos w/w) ear tags @cation 6). Signiscant differences (Pr0.05) h a n Ectoguardœ and the non-treated anunals are indicated by an a*aisk (9.
Mean number of horn nies per side (n=10) O C cn
O O $ a Pretreatment
May 30
Jun 4
15
2 1
28
Jd 2
10
17
24
3 1
Au@ 10
17
24
3 1
Sep 8
14
2 1 J
~ r l Mean number of hom flies per side (n-10)
May 30
Jun 4
15
21
28
Jul2
I O
17
24
31
Aug 10
17
24
31
14
21
(O ~ = u ) app rad sa!U woy p raquinu ueaw
Fenvalerate LC, values and raistance ratios for pyrethroid and
organophosphorous-resistant honi flies nom Perth and Glenm, Ontario, and susceptible
horn flies nom Rockwood, Ontario, are presented in Table 2. Dose-response cwes for
al1 fenderate bioassays are presented in Figures 12 - 14. Susceptible hom nies collecteâ
for raistance ratios determined August 20121 were nOm a Rockwood daky k d that had
been exposed to a 0.5% pyrethrin barn spray on August 6, 1998 (Tim May, R.R 3,
Rockwood ON). This spray may have selected for flies more tolerant to fenderate and
therefore may have lowered the resistanct ratios.
Table 2 LC,, LC, and resistance ratios of pyrethroid and organophosphorous-rcsistint hom nies from Perth and Gltncot, Ontario, and susceptible flics trom Rockwood, Ontario, determincd afttr 3 hours exposun to fenvalerate, 1998.
Dite Source EN EH Slope Resictance Ratio - -
July 10 Pe fth 0,038 0.32 1,77 (0.026,0.059) (O. 15,2.09) 253
Iuly 1 1 Rockwood 0.15 x 105 0.1 1 x 1W2 1.89 (0.99x104,00.20x10-3) (0.64x10",0.45~10-~)
- -
August 20 Perth 0,041 1 ,O4 1.17 (0.024,0.061) (0.43,7.65) 1 OS
August 2 1 Rockwood 0.38 x lu3 0.18 x. 1c2 2.72 .+ (0.25 x 1@, 0.56 x W3) (O. 13 x IO'*, 0.37 x 10'3
LC, and LC, values are expressed in &cm2 (95% confidence limits). Resistance ratios are dotedned as RLCdSLC,.
SusceptiMe hom fiy population
Resistant hom fly population - - - - 95% confidence limits
Concentration of fenvale rate pglcm2
Figure l2 Mortality dose-response with 95 % confidence limits for pyrethoid and organophosphorous-resistant hom flies (Haematobiu irnlon~) LCm=0.038 fiom Perth, Ontario, and susceptible flies LCm =O. 1SxlV fiom RockWood, Ontario, e x p d to fenderate for 3 hours, h l y 10/11, 1998.
Susceptibte horn fly population Resistant horn fly population
---- 95% confidence limits
I o5 1 0 ~ 1 o - ~ 1 0-1 1 00 I O'
Concentration of femlerate Clglcd
Figure 13 Mortaiity dose-response with 95% confidence limits for pyretbroid and organophosphorous-resistant hom flies (Hoenxatobia U350 = 0.41x10-' from Perth, ontario, and suscepti'ble flies LC50 =0.45xlU3 fiom Rockwood, Ontario, e x p e d to fenvalate for 3 hours, August 20121, 1998.
SusceptiMe hom fiy population Resistant hom fiy population - - - - 95% confdence limits
Concentration of fenvalerate j@cm2
14 Mortaiity dose-response with 95 % confidence limits for pyrethroid and organophosphorous-resistant hom flies (Haem4tobia imlms) LC,=O. 12 from Glencoe, Ontario, and susceptible flies LC,=0.45xlV fiom Rockwood, Ontario, exposexi to fenvalerate for 3 hours, August 20121, 1998.
4.2.2 LMàzhn Bioassay
Diazinon LC, values and resistance ratios for pymhroid and organopho~phorous-
resistant horn flies fiom Perth and Glencoe, Ontario, and susceptible aies fiom Rochivood,
Ontario, are presented in Table 3. Do~e-response cums for the diazimn bioassays are
plotteci in Figures 15 and 16. The resistanoe ratios obBerved for diazinon raistant dies
were low compared to resistance ratios observeci for tizmderate resistant flies. However,
MIme of both organo~hosphorous tags (protectoi 20% diazinon, and ~ctogupid. 10%
tetrachlorvinphos) indicate that mistance to organophosphorous insecticides is a problem.
-
Table 3 LC,, LC, and resistancc ratios of pyrethroid and organophosphorous-resistant horn nies from Perth and Glencoc, Ontario, and susçeptible flics from Rockwood, Ontario, dttermincd alter 24 houra cxposure to diazinon, 1998.
August 2 1 Rockwood O, 59 3.18 2,48 (0.44,0.74) (2.43,4.69)
August 21 Glencoe 1.94 12,54 1,38 3,3 (1 .25,2,92) (7.26,30.59)
LC, and LC, values are expressed in @cm2 (95% confidence limits). Resistance ratios are determined as RLCdSLCM.
1 0 Susceptible hom fiy population 1 1 . Resistant hom fly population - - - - 95% confidence limits
Concentration of diazinon Iig/m2
Figure 15 Mortality dose-response with 95% confidence limits for pyrethroid and organophosphorous-nsistant horn flies (Haematobia im'tm) Km = 1-29 from Penh, Ontario, and susceptible flies LC,=O.S9 from Roc-, Ontario, exposed to diazinon for 24 hours, August 20/21, 1998.
a SusceptiMe horn ffy population Resistant hom fly population ---- 95% confidence limits
-.
I
.4 r
4
6'
l
r
10-5 1 o4 i o3 1 o - ~ 1 O-' 1 o0 1 01
Concentration of diazinon pg/cm2
Fgve 16 Mortality dose-response with 95% confidence l i m h for pyrethroid and organophosphorous-resistant hom flies (Hmltcofobia im'tum) = 1.94 fiom Glencoe, Ontario, and susceptible aies &=OS9 fkom Rochvood, Ontario, exposed to diazinon for 24 hours, Auguft 20/21, 1998.
(Sheppard and Joyœ 1998). m l t e d in 100% mortdity of pyrethioid and
organophosphotou~-rais- and suscepbiile ' horn fly strains. Therefore, lower
concentrations were prepared so that a differential mortaiity was observable. The
chlorfenapyr LC, values for resistant Perth and Glencoe horn fly populations were
determined as 0.013 pgfcrn2 and 0.012 pgfcm2, respectnieLy. September 4 and 5, 1998.
Dose-response moctality of pyrethroid and organophosphomus-mistant horn flies fiom
Perth and RockWood, Ontario are presented in Figure-s 17 and 18, mpectively. Mortality
of pyrethroid and organophosphotous-supceptible horn f lks fiom RockWood was 100 % at
al1 levels tested (lowest concentrations tested was 1.25 x 1W2 rcgLcm3. 'IbeJe preliminuy
results suggest that chlocfenapyr resistance wuld develop in orgamphosphorous and
p yrethroid-mistant horn flies because LC,,,s for resistant flies are alrrody higher thPn for
susceptible flies. These results disagree with those of Sheppard ami Joyce (1998) who
observed a 5 fold increased sensitivity to chlorfenapyr in pyrekoii-cesistant horn flies as
compared to a susceptible strain. Sheppard a d Joyœ (1998) predict that high levels of
rnixed function oxidases in pyrethroid resistant horn flies (Sheppard 1995) are responsible
for a rapid conversion of chlorfenap yr to the active toxic form AC 303268.
Hom fly population 95% confidence limits
Concentration of chlorfenapyr p@cm2
Flgure 17 Mortality dose-response with 95% confidence limits for pyrethroid and organophosphorous-resistant horn flies (Haemc~tobia irn'tans) LCm=0.013 fmm Perth, Ontario, exposed to chlorfenapyr for 24 hours, Septernber 4, 1998. Monality of susceptiile flies from Rockwood, Ontario, was 100% at al1 concentrations presented.
I Hom fiy population 95% confidence limits
i o4 103 1 1 O-'
Concentration of chlorfenapyr Crg/cm2
Figure 18 Mortality dose-response with 95 % confidena limits for pyrethroid and organophosphorous-resistant hom flies (Haematobia irritaas) Km =0.012 from Glencoe, Ontario, exposed to chlorfenapyr for 24 houn, September 5, 1998. Morraiity of suscepa%le flies from RockWood, Ontario, was 100 % at al1 concentrations presented.
4.4 Colorimetrîc Acetykholinesterase Asay
The effects of diazinon on pyretïuoid and organophosphorous-resistant and
susceptible hom fly acetylcholinestense activity are presented in Figure 19.
Acety lcholinesterase activity of exposed fly heads k exprwsed as a percent of non-exposed
wntrol values. Mean activity in control aies for the thrœ populations tested (Perth,
Glencoe, and Rockwood, Ontario) mis aot significantly différent at Pr0.05 (Student's t-
test). Mean activity at 100% was 89.8 nmoIehg protcia/mia. PreIiminsry mdts
demonstrate thM the pyrethroid and otganophosph~f~~~-cesistant Perth rid Glencoe
populations had 10 - 50% Iess acetylcholinestcrase inhibition than the susceptible
Rockwood population when expoaed to mmentrations ofdiazinon. The mistant Perth Pnd
GIencoe horn Oies may have a reduced sensitivity to ~atylcholinesteraae inhibition by
diazinon, and for may metabolically degrade diazinon at a higher rate than the suscepti'ble
population (Guerrero et al. 1999). Low fly collection numben in August 1998 at the P d
location lirnited the number of heads available for the wlorimeaic iuxtylcholiaestetase
assays and as a result the assays were based on one collection &te. Further research is
recommended.
Percent inhibited acetylchollnesterase activlty after 24 houn of expsosure
5 CONCLUSIONS
Failure of proteclor' (20% diazinon wlw), ~ctoguard* (10% tetrachlorviaphos
(11 56 diazinon, 6% cypermethrin) tags, and LC, biuassay results indicate that horn flies
in Perth, Ontario have developed multiple resisîanœ to p p t h i d and a&uropbDBphosphorops
iosecticides used in impregnated cpttle ear tags. LC,,, bioessays tevealed thnt ~ie~istance
to fenvalerate (Surgeoner et ai. 19%) has remaïneci high (mistance ratio 289) in horn flics
from Glencoe, Ontario. The resistame ratio detemined for diazioon (3.3) and repotted
lack of control with pyrethroid and organopbosphorous impregnated ear tigs implies that
multiple resistance exists in Glencœ. Resistaace of horn flies to organophosphorous
andor pyrethroid insecticides impregnated in cattle ear tags is a fairly recent development
in Ontario. Surgeoner et al. (1994) and Lindsay et al. (19%) were the fint to document
horn fl y resistance to pyrethroids in Glencoe and organophosphorous insecticides in Perth,
respectively. MultipIe mistance to organophosphorous and pyrethroid insecticides bas not
been documented in Ontario prior to this thesis rrsuuch. However, horn fiy resistance in
Ontario is not as severe a problem as in the USA where resistance ratios have reached
600x in the fieid for pyrethroids and 1ûx for organophosphorous insecticides (Butler
1999).
Effective reduction of horn flies with impregnated tags cumntiy available is no
longer a control option in the Perth and Glencoe areas. Producers in the Perth area may
be able to retum to the ~liminator' (1 1 % diazinon, 6 96 cypermethrin) tag which provided
60.1 - 71.7% season reduction, but must fint use a strategy that has a different active
ingredient (such as the avermectùi pour-on, ~vomsc'). Producers in al MU of Ontario
m u t rotate insecticide mode of action on a yearly b i s a d shodd remove impregiirtcd
ear tags at the end of ihe seamn to prevent M e r resistanœ deveIopment, Also, the irse
of alternative methods of application, e.g. back rubbers, pour-ons and sprays, although
often more costly and labour intensive, may prolong the usefulncss of pyrethids and
organophosphorous insecticides for the control of hom nies in meas where mirbure has
not yet occurred.
Evaluation of a potential new active ingredient for ear tsgs. chlorfenapyr (AC
303630). by glas tube bioassay demonsmted excellent cesistant anci susceptiile fly
mortality (100%) at al1 concentrations suggested by Shepperd and Joyce (1998),
0.1 pg/cm2 to 0.8 fig/cm2. At concentrations ranging from 1.25 x 1C2 pg/cm2 to 0.2
pg/cm2, pyrethroid and organophosphorous-cesistant nies from Perth and Glencoe,
Ontario. were less sensitive to expure than the susceptiile flies nom RockWood,
Ontano. Although the differential mortality observed in the resistant populations may
suggest the potential for resistance development to chlorfenapyr, the high mortality
achieved in both resistant and susceptible horn fly populations îdicate that chlorfeaapyr
could be a useful new tool for horn fly management.
Preliminaty results of colorimetric assays demonstrated higher l a
acety lcholinesterase inhibition (10-50 1) in pyrethroid and orgamphosphorous-resistant
horn tlies than in susceptibles when exposed to concentrations of diazinon.
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