Journal of Medical Entomology (2008) 45, 905-911

Robert J. Miller, Andrew Y. Li, Mary Tijerina, Ronald B. Davey and John E. George (2008)
Differential response to diazinon and coumaphos in a strain of Boophilus microplus (Acari: Ixodidae) collected in Mexico
Journal of Medical Entomology 45 (5), 905-911
Abstract: Boophilus microplus, collected from Nuevo Leon, Mexico, were found to be highly resistant to diazinon but not highly resistant to coumaphos, suggesting that different mechanisms of resistance were present in these ticks than other Mexican organophosphate (OP)-resistant ticks reported previously. When exposed to coumaphos and piperonyl butoxide or triphenylphosphate, the LC₅₀ estimate was reduced by 3.5- and 6.3-fold, respectively, suggesting that mono-oxygenases and/or esterases were involved in resistance to coumaphos. Additionally, it was determined that this strain had an Acetylycholinesterase (AChe) that was insensitive to the active form of coumaphos, coroxon, taking at least 24 min longer to reach 50% reduction in AChE activity compared with the susceptible strain. When exposed to diazinon, none of the synergists tested significantly lowered the LC₅₀. However, it was determined that it took six times longer to reach 60% inhibition of AChE in the resistant strain compared with the susceptible strain when exposed to the active form of diazinon, diazoxon. Insensitive AChE seems to be very common in OP-resistant B. microplus. The potential benefits for the development of a field-portable AChE inhibition assay kit are discussed.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website
Database assignments for author(s): Andrew Li, John E. George, Ronald B. Davey

Research topic(s) for pests/diseases/weeds:
pesticide resistance of pest

---

Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Rhipicephalus microplus		Mexico