Brun, Luc-Olivier

Horizon / Pleins textes

J.  Aust. ent. Soc., 1992, 31: 301-302 301 
RESISTANCE TO DELTAMETHRIN IN BOOPHILUS MICROPL US 
(CANESTRINI) (ACARINA: IXODIDAE) IN NEW CALEDONIA 
i 
L. O. AB^^^ 
E 
ORSTOM, Institut Français de Recherche Scientifique pour le Développement en Coopération, B. P.‘ A 5, Nouméa, 
New Caledonia. 
Abstract 
A strain (S) of Boophilus microplus collected from the east coast of New Caledonia was compared 
with a strain (R) from the west coast for resistance to deltamethrin. The R strain was significantly more 
resistant than strain S with a 5.7 fold resistance factor determined at the LDro using the larval packet 
technique. This is the first report of synthetic pyrethroid resistance in B. microplus in New Caledonia. 
Since its accidental introduction to New Caledonia in 1942, the cattle tick Boophilus microplus 
(Canestrini) has been controlled successfully through dipping or spraying with the following acaricides: 
Cooper’s arsenic dip (1943-1950); Rucide (DDT, 1950-1973); Rhodiacide (ethion, 1973 until the present 
on some farms). 
In 1980; control failure with ethion led to the demonstration of a highly resistant strain (Brun et al. 
1983) from the Thio region. Following a large B. microplus outbreak and death of cattle, ethion was replaced 
on this farm by Butox (deltamethrin) in November 1982. Butox was initially used in alternate years with 
Bayticol (flumethrin) and then continuously since 1987. As control problems were recently reported with 
deltamethrin, laboratory tests were conducted on a strain from this particular location to check for resistance. 
Two field strains were compared: a susceptible strain (S), with no history of exposure to deltamethrin, 
collected from Poya on the west coast; and a second strain (R) from a beef cattle farm in the Thio region 
experiencing control problems with deltamethrin. Cattle ticks from this farm were also the first record 
for ethion resistance in New Caledonia (Brun et al. 1983). 
The strains were compared using the FAO recommended dosage-mortality technique (Stone & Haydock 
1962; Anon. 1971) for detecting and measuring acaricide resistance. Both strains were collected in August 
1991, and brought to Nouméa for study. 
Females were cultured at 27 f 1 OC and 85-90% r.h. for about 4 weeks for oviposition and hatching. 
Unfed larvae were dropped into impregnated paper packets in clusters of about 100-200 with each treatment 
replicated three times. The packets were then stored flat in an incubator under the same controlled 
temperature and humidity conditions for 24 h before mortality assessment. Ticks able to move were counted 
as alive. 
Strain S had a LDfo of 14.2 ppm (95% fiducial limits 13.1-15.4) with a slope of 4.81 (S.E. 0.15). 
Strain R had a LDro of 81 ppm (95% fiducial limits 64.7-102.4) with a slope of 2.79 (S.E. 0.07). Strain 
R had a resistance factor of 5.7. 
As previously demonstrated in Australia after about 20 years’ non-use of DDT (Roulston et al. 1981), 
a survey for DDT resistance in New Caledonia has shown that the DDT resistance gene was still detectable 
although this compound has been banned since 1973 (Brun et al. 1984). In this previous study, the DDT 
resistance of ticks from the R strain was demonstrated using a 2% discriminating dose and only 97.7% 
mortality was observed. Because of the presence of resistance to DDT in the field, and the cross resistance 
demonstrated elsewhere (Nolan et al. 1977), the significance of this first pyrethroid resistant strain in New 
Caledonia should be investigated. In Australia, control of the DDT-resistant strain (DDT-R) cross resistant 
to pyrethroids was achieved with increased concentrations (Nolan et al. 1979), and was enhanced by 
organophosphorus (OP) compounds (Nolan and Bird 1977). Although the R strain from Thio should be 
controlled by a similar approach, the recent occurrence of three new pyrethroids resistant strains causing 
serious implications for chemical control in Queensland (Nolan et al. 1989) raises important concerns for 
the future of synthetic pyrethroids in controlling cattle tick in New Caledonia. 
Acknowledgments 
and correction of the manuscript. 
I am indebted to Mr C. Marcillaud for technical assistance and Dr D. M. Suckling for comments 
References 
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[Manuscript received 20 November 1991. Accepted 27 March 1992.1 


Resistance to deltamethrin in Boophilus microplus (Canestrini) (Acarina: Ixodidae) in New Caledonia

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