Baseline susceptibility and cross‐resistance in Aphis gossypii Glover (Aphididae: Hemiptera) to phorate and sulfoxaflor

Susceptible discriminating doses of phorate (0.2 g/L) and sulfoxaflor (0.01 g/L) against cotton aphid Aphis gossypii Glover were determined by laboratory bioassay where aphids were sprayed with insecticide with the aid of a Potter spray tower. All of the populations tested were susceptible to sulfoxaflor, and only a pirimicarb resistant strain had cross‐resistance to phorate. If phorate is used as a side dressing in Australian cotton for insect control, neither pirimicarb, or any other chemical associated with insensitive acetylcholinesterase type one resistance, should be used as the first foliar spray for any subsequent aphid control.