Toxicological effects and resistance to pyrethroids in Boophilus microplus from Goiás, Brazil

Abstract

In order to monitor the susceptibility of Boophilus microplus to acaricides and improve control measures, the effects of cypermethrin, deltamethrin and permethrin on larvae obtained in the city of Goiânia in the Brazilian state of Goiás were studied. Although these pyrethroids are already sold as acaricides, their cost-benefit efficiency has been questioned. Fasting 14-21 day-old larvae were immersed in solutions of the acaricides under test, maintained at 27±1° C, and relative humidity over 80%, and observed under the stereoscope within an apparatus originally designed for studying the non-parasitic phase of the tick life cycle. The observed toxicological effects were: excitability, repetitive motion, decreased motor ability, detachment, paralysis, knock-down and cuticular proliferation of liquids and gases. The materials used in the manufacture of this apparatus consisted of disposable Petri dishes, "organza" cloth and paraffin, none of which are toxic to tick larvae. Mean death rates after 24h were 76.3%, 87.5%, 77.6%, 91.2%, 86.2% and 100% for 25 and 50ppm deltamethrin, 150 and 300ppm cypermethrin and 1250 and 2500ppm permethrin, respectively. The ticks were resistant to commercial concentrations of deltamethrin and cypermethrin. Only 2500ppm permethrin produced the mortality recommended by the Brazilian Ministry of Agriculture.

Evaluation of Rhipicephalus (Boophilus) microplus (Acari: Ixodidae) resistance to different acaricide formulations using samples from Brazilian properties

“…Ticks resistant to the product "alpha-cypermethrin 15 g" were found on a property in Brasília, which is also in the mid-western region of the country. This result confirms results obtained in Goiás, where only pyrethroids had efficacy below the recommended level (SILVA et al, 2000;FERNANDES, 2001).…”

Comparative in Vitro Study on the Efficacy of Some Commercial Insecticides against Rhipicephalus (Boophilus) annulatus Ticks

“…) annulatus larvae at the 3 rd day post treatment which was in agreement with Trevino, (1976) who found that diazinon at concentration of 250 µg/ml caused 100% larval mortality after 3 days of B. microplus. While Butox ® 50 insecticide reached 93.3% efficacy at both dilutions (1 ml/l and 2 ml/l) also after 3 days post treatment and this result was in harmony with results obtained by Fernandes et al, (2001) who found that the lethal capacity of deltamethrin against hard tick larvae of R. sanguineus after 30 hours was low, and the mean mortality percentages were 34, 40.2, 46, and 57.6 % after treatment with 0.5, 1, 2, and 3 ml/l, respectively. While disagreed with Cetin et al, (2009)who exposed larvae of A. persicus for 15 min to ceramic tiles treated at field application rates with deltamethrin (Impotek DMT_EW, 0.01 g ai/m 2 ) and they found that the deltamethrin achieved complete mortality at 1 hour post treatment.…”

Toxicity of extract of Magonia pubescens (Sapindales: Sapindaceae) St. Hil. to Control the Brown Dog tick, Rhipicephalus sanguineus (Latreille) (Acari: Ixodidae)

“…The females were placed in BOD incubators acclimatized to 27 ± 1ºC, RH > 80% and a 12:12h photoperiod. In order to obtain larvae of the same age, eggs batches were daily collected in separate polyethylene tubes with screw caps (Fernandes 2000(Fernandes , 2001). …”

“…The bioassays were carried out in a BOD incubator under the same conditions as described previously (Fernandes 2000(Fernandes , 2001. Larvae were exposed to the solutions in fi lter papers envelopes ( 327 cm 2 ), containing micropores to ensure adequate circulation of air.…”

“…In order to obtain larvae of the same age, eggs batches were daily collected in separate polyethylene tubes with screw caps (Fernandes 2000(Fernandes , 2001). An established method was used to determine larval susceptibility to plant extract impregnated fi lter paper, "the larval packet test (lpt)" (FAO 2004), incorporating slight modifi cations to improve practicality and reduce cost without compromising effi ciency (Fernandes 2000.The bioassays were carried out in a BOD incubator under the same conditions as described previously (Fernandes 2000(Fernandes , 2001. Larvae were exposed to the solutions in fi lter papers envelopes ( 327 cm 2 ), containing micropores to ensure adequate circulation of air.…”