Patterns of Resistance to Various Acaricides in Some Jamaican Populations of Boophilus microplus12

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Abstract
Relative susceptibility of 6 Jamaican strains of the southern cattle tick to 15ndash;26 acaricides was determined by bioassay on 2- to 3-wk-old unfed larvae. Propoxur, promecarb, dimethoate, phosphamidon, and diazinon were the most toxic while ppDDT and dicofol were the least toxic to almost all strains. Lindane and chlordimeform were among the most effective acaricides on some and least effective on other strains. The Jamaican strains displayed certain levels of specificity in their responses to an acaricide. Carbaryl, propoxur, dicofol, ppDDT, and most organophosphates were almost evenly toxic; differences in LC50 values between any 2 strains were less than 7-fold. However, allyxycarb, naled, promecarb, chlorfenvinphos, dimethoate, fenitrothion, dicrotophos, chlorphyrifos, and crotoxyphos had 11- to 105-fold differences in their toxicity, while the LC50 values of pirimiphos methyl, lindane, and chlordimeform varied by ca. 226-, 1470-, and 25,800-fold, respectively. Comparison with the susceptible Yeerongpilly strain reveals that 4 strains have developed ca. 9- to 16-fold resistance to carbaryl; one had 31-fold and 3 others had ca. 143- to 165-fold resistance to lindane. St. Thomas strain was ca. 31- and 65-fold resistant to dimethoate and dicrotophos while the St. Ann and Clarendon strains were ca. 20- and 69-fold resistant to chlorfenvinphos and crotoxyphos, respectively.