Inhibition of carbamate-insensitive acetylcholinesterase by piperonyl butoxide in Helicoverpa armigera.

The cotton bollworm, Helicoverpa armigera, is a cosmopolitan, insecticide-resistant insect pest of food and fiber (Gunning et al., 1992). Acetylcholinesterase (AChE) is the insect target site for carbamate insecticides, and H. armigera has developed an insensitive form of AChE as a resistance mechanism (Gunning et al., 1996). Insensitive AChE is normally considered an intractable resistance mechanism in pests. The methenedioxphenyl compound, piperonyl butoxide (PBO), has a long history as an insecticide synergist in the control of resistant arthropod pests; it is known to inhibit mono-oxygenases and nonspecific esterases (Gunning et al., 1998). This work discusses PBO inhibition of AChE in H. armigera and explores synergism.