Incidence and characterization of resistance to pyrethroid and organophosphorus insecticides in Thrips tabaci (Thysanoptera: Thripidae) in onion fields in Isfahan, Iran

• Thrips tabaci populations showed widespread resistance to OPs and pyrethroids.
• Enhanced detoxification played a major role in resistance to organophosphates.
• T929I target-site mutation was detected in pyrethroid resistant populations.
• Resistant populations show cross resistance to other tested OPs and pyrethroids.
• No cross-resistance was detected to acetamiprid, spinosad and azadirachtin.

ABSTRACTOnion thrips, Thrips tabaci Lindeman, is the main pest of onion-growing fields in Isfahan and is mainly controlled by frequently spraying several insecticides. To investigate the resistance status and mechanisms, the susceptibility of ten field populations collected from Isfahan onion-growing regions were tested to several currently used pesticides. Resistance to the tested insecticides was observed in most populations when compared with the susceptible reference population. Enhanced detoxification, implicated by the use of inhibitors of major metabolic detoxification enzymes, was observed in the populations resistant to profenofos and chlorpyrifos. In the deltamethrin resistant populations, the amino acid substitution T929I was detected in the voltage gated sodium channel, which is known to confer pyrethroid resistance. These data are a first step towards more efficient resistance management tactics through early detection of resistant onion thrips in Iran.

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