OXIDATIVE METABOLIC RESISTANCE TO CYANOPYRETHROIDS IN THE HORN FLY (DIPTERA, MUSCIDAE)

I propose that the high level of resistance to cyanopyrethroids found in cyhalothrin-selected horn flies is caused by an enzyme system that oxidatively inactivates the cyano group. This theory is supported by lower resistance to noncyano pyrethroids, lower response to the synergist piperonyl butoxide with noncyano pyrethroids, resistance ratios and synergism coefficients among the cyanopyethroids that follow a pattern predicted by chemical stability of the molecule, and reported literature of distinctly different responses to cyano and noncyano pryrethroids in other animal systems.